THE REPRODUCTIVE SUCCESS OF
THE HOODED MERGANSER (Lophodytes cucullatus) AT
MOSQUITO CREEK WILDLIFE MANAGEMENT AREA
by
Kimberly S. Ludt
Submitted in Partial Fulfillment ofthe Requirements
for the Degree of
Master ofScience
in the
Biological Sciences
Program
YOUNGSTOWN STATE UNIVERSITY
July, 2003
The reproductive success ofthe Hooded Merganser (Lophodytes cucullatus) at
Mosquito Creek Wildlife Management Area
Kimberly S. Ludt
I hereby release this thesis to the public. I understand this thesis will be housed at the
Circulation Desk ofthe University Library and will be available for public access. I also
authorize the University or other individuals to make copies ofthis thesis for scholarly
research.
Signature:
Approvals: ~ .:J!dOC!3
Date
ABSTRACT
The goal ofthis study was to examine factors that influence the reproductive
success ofhooded mergansers, Lophodytes cucullatus, nesting at Mosquito Creek
Wildlife Management Area (MCWMA). I examined nesting activities ofthe hooded
merganser at MCWMA from March through July 1998. I collected at least two
unincubated hooded merganser eggs from active nests to determine eggshell thickness
and organochlorine (OCs) concentrations. My data were compared with an intensive
study ofnest boxes at MCWMA in 1994 and 1995 and with previous studies and
historical collections ofeggshells.
The mean eggshell thickness ofhooded merganser eggs was 0.605?0.004 mm,
9% thicker than a previous study done in 1981. Based on eggshell thickness, it appears
that OCs are not a concern. However, results ofthis study indicate a population of
nesting hens that appear to be stressed by high nest density. An increase in nest box use
from 21% (1994-1995) to 33% (1998) was inversely correlated with a decrease in nesting
success from 80% (1994-1995) to 69% (1998). In addition, a significant decrease in
hatching success was noted from 90% (1994-1995) to 79% (1998) (p<0.05) while
intraspecific nest parasitism increased from 13% (1994-1995) to 75% (1998). In
conclusion, it appears that reproduction in this population ofhooded mergansers is being
influenced by nest box management, which promotes high density nesting, high levels of
parasitism and nest abandonment, and not by external factors, such as environmental
contaminants.
iii
ACKNOWLEDGMENTS
Sincerest thanks to my advisor, Courtenay Willis, for her guidance, patience, and
encouragement throughout this journey. I thank her for turning my ears and eyes to an
avian world I never knew. And I sincerely thank Renee Falconer for all her support and
guidance and for giving me a greater appreciation ofchemistry. I thank both Courtenay
and Renee for not giving up on me.
I would like to acknowledge Dr. Usis, Dr. Martin, Dr. Schroeder, and Dr.
MacLean for their support and the YSU Biology Department. I am grateful to Andi
Leone for running my samples. I thank Lloyd KiffofThe Peregrine Fund and Gary
Heinz from Patuxent Wildlife Research Center for their advice and Matt Phillips for
measuring eggshell thicknesses. Thanks to Mike Renner and Jim Grahl ofthe Ohio
Division ofWildlife for all their assistance at Mosquito Creek Wildlife Management
Area. I am truly appreciative ofmy supervisor, Tim Morgan, for encouraging me and
allowing me to take time offwork to complete my thesis.
I am indebted to my friends and family that helped me check nest boxes no matter
what the weather; Courtenay, Bob Ludt, JeffDick, Jason Anderson, Lisa Clouser,
Shannon DiBell, Erica Richards, Kim Mascarella, Ryan Alter, Dave Hochadel, Scott
Crawford, and Corina Crawford. They helped to make each trip to the nest boxes an
adventure.
I will be forever grateful to my parents for their love and support and giving me
the opportunity to attend college. Above all, I thank my husband for all his love,
patience, and understanding through my field work and writing.
IV
TABLE OF CONTENTS
ABSTRACT 111
ACKNOWLEDGMENTS IV
LIST OF TABLES V11
LIST OF FIGURES.......................................................................... V111
CHAPTER PAGE
I. INTRODUCTION
Natural History ofHooded Mergansers... 1
Factors Influencing Reproductive Success. 4
Use ofOrganochlorines..... ... ........ 4
Organochlorine Impacts on Birds. .. ... 8
Susceptibility ofHooded Mergansers 11
Occurrence ofNest Parasitism 13
II. METHODS
Null Hypotheses 15
Study Site " ............... .. 15
Behavioral Observations 20
Nest Box Checks 20
Collection ofSamples 21
Egg Analysis " .... ...... ........ 22
Water Analysis 26
Sediment Analysis " ..... 27
GC Analysis " ......... ........ 28
Statistical Analysis............ ...... ..... ................... ...... ... .. .. 28
II. RESULTS
Behavior Observations........ .................. ............ ... ... ... .... 30
Laying Chronology..... .. .. ... ... ........ ...... ... .... .. ...... .. .. . . 30
Egg Parameters 33
Nest Box Summaries 36
Parasitism " " ............ .......... ......... 42
Lab/GC Analysis............... ...... .............. ................... .. .. 47
III. DISCUSSION
v
Laying Chronology. .... ............. ... ............................. .......... 48
Egg ParaIlleters................................................................. 49
Eggshell Thickness............................................................ 49
Reproductive Success and Parasitism ofHooded Merganser............ 51
Reproductive Success and Parasitism ofWood Ducks................... 53
Lab/GC Analysis.............................................................. 54
Conclusions.................................................................... 56
Future Work............... ................................................... 56
REFERENCES......................................................................... 57
APPENDIX A
Field Data................................. ........ ......................... ... 63
APPENDIXB
Equations 74
vi
TABLE
LIST OF TABLES
PAGE
1. Hooded merganser eggshell thickness comparisons (mean ? SE) from previous
studies and historical collections. A decrease in eggshell thickness is shown from the
pre-OC era, through OC use, and after most OCs were banned in the late 1970's....12
2. Summary ofhooded merganser nest box activity at MCWMA. The data from this
study was compared to a study done in 1994 and 1995 on the same ponds using 2x2
contingency tables (Willis 1996) .40
3. Summary ofmeans and standard error ofsuccessful hooded merganser nests at
MCWMA. Means and standard error are also shown for parasitized (intraspecific)
and non-parasitized hooded merganser nests for comparison .41
4. Summary ofwood duck nest box activity at MCWMA. The data from this study was
compared to a study done in 1994 and 1995 on the same ponds using 2x2 contingency
tables (Willis 1996) 43
5. Intraspecific and interspecific nest parasitism summaries ofhooded merganser and
wood ducks at MCWMA. The data from this study was compared to a study done in
1994 and 1995 on the same ponds using 2x2 contingency tables (Willis 1996) .46
6. Comparison ofeggshell thickness ofhooded mergansers at MCWMA with previous
studies and historical collections. A decrease in eggshell thickness is shown from the
pre-OC era, through OC use, and after most OCs were banned in the late 1970's. In
1998, hooded mergansers using nest boxes at MCWMA appear to have eggshells
close to pre-OC era thickness 50
7. Field measurements for eggs measured at Eagle (E) and Wood Duck (WD) Marsh.
Sample #'s indicate eggs that were collected for lab analysis 63
8. Field and lab measurements for 83 eggs collected from Eagle (E) and Wood Duck
(WD) Marsh 69
9. Nest box summaries for hooded mergansers and wood ducks nesting at MCWMA.
D = drop nest, T = tree swallow nest, G = grackle nest, A = abandoned nest, P =
predated nest, S = successful nest 71
vii
FIGURE
LIST OF FIGURES
PAGE
1. Location ofstudy site at Mosquito Creek Wildlife Management Area in Trumbull
County, Ohio 17
2. Location ofnest boxes used for this study at Eagle Marsh and Wood Duck Marsh...19
3. Topographic map ofstudy site at MCWMA. Numbers on each pond indicate the
location ofwater and sediment samples 24
4. Chronology ofhooded merganser egg laying at MCWMA. Time 1 = March 24,
when first eggs were found. Each block represents 10 days with the first block
starting at 1 32
5. Chronology ofwood duck egg laying at MCWMA. Time 1 = March 24 when first
eggs were found. Each block represents 10 days with the first block starting at 1.....35
6. Correlation between reproductive success ofhooded mergansers and eggshell
thickness at MCWMA. Reproductive success was determined from the % ducklings
that hatched in successful nests (# eggs hatched/# eggs laid). The correlation
coefficient (r8 ) was 0.444, P=O.232 (SPSS 1998) .38
7. Interspecific nest parasitism ofan active hooded merganser nest at MCWMA.
Hooded merganser eggs are white, considerably larger, and more spherical than wood
duck eggs, which are beige, smaller, and more elliptical .45
Vlll
1
INTRODUCTION
The goal ofthis study was to examine factors that influence the reproductive
success ofhooded mergansers, Lophodytes cucullatus, nesting at Mosquito Creek
Wildlife Management Area. My objectives were (1) to compare local organochlorine
levels and eggshell thickness with data from previous studies and historical eggshell
collections, (2) to correlate the eggshell thickness ofunincubated hooded merganser eggs
and reproductive success ofhooded mergansers using nest boxes, and (3) to determine if
nest box parasitism has influenced the nest box use and reproductive success ofhooded
mergansers at MCWMA over the past five years.
Natural History ofthe Hooded Merganser
The hooded merganser is a small North American duck in the tribe mergini (Batt
1992). It measures approximately 45 cm in length and 700 g in weight (Bellrose 1976),
comparable in size to the wood duck, Aix sponsa. It is the smallest ofthe mergansers.
Long, narrow, serrated bills distinguish them as a merganser. Male and female hooded
mergansers are sexually dimorphic most ofthe year (Dugger et at. 1994). The male is
mostly black and white with a white crest bordered in black. The female is brown with a
grayish brown crest. Both sexes have white wing markings on the secondaries and
tertials (Gooders and Boyer 1986, Bellrose 1976).
The breeding range ofthe hooded merganser is found throughout the northern half
ofthe US and southern Canada (Phillips 1986). They are more commonly found in
forested areas in the Great Lakes region (Dugger et at. 1994). Eastern birds winter
mainly in the southeastern United States and western populations winter around northern
2
California (Bellrose 1976, Root 1988). However, wintering mergansers can be found
throughout the entire southern United States, north ofMexico (Bellrose 1976).
Wooded streams, sloughs, and ponds in swamps are habitat preferred by the
hooded merganser (Bellrose 1976). However, nests have been recorded in grasslands in
man-made boxes in Minnesota (Zicus and Hennes 1988) and in non-forested riparian
corridors in North Dakota (Doty et al. 1984).
The population size ofthe hooded merganser is not very well known due to its
secretive nature. In 1976, the population was estimated to be around 76,000 individuals
(Bellrose 1976). However, due to the 70,000 to 100,000 birds harvested each year by
hunters (U.S. Department ofthe Interior 1988), this is likely an underestimate. Based on
harvest numbers, estimates ofannual survival, and an assumption of100% annual
mortality due to hunting, estimates lie between 270,000-385,000 birds (Dugger et al.
1994). Nest box management may be effective in increasing local hooded merganser
populations.
Hooded mergansers are top predators in aquatic ecosystems. They forage visually
by diving in clear aquatic habitats, such as forested ponds, rivers, streams, and flooded
forest. Their slender serrated bill is used for grasping and handling mobile prey such as
fish and aquatic insects (Dugger et al. 1994).
Prior to arriving on breeding grounds, hooded mergansers are paired. At
Mosquito Creek Wildlife Management Area in northeastern Ohio, hooded mergansers
arrive from late February to early March. Shortly after arrival, females begin checking
nest boxes and/or tree cavities. They also use pre-excavated cavities, commonly from
pileated woodpeckers (Dryocopus pileatus) in both living and dead trees within close
3
proximity to water (Morse et al. 1969). Nest boxes are typically placed over or near
water and are filled partially with wood chips. Nest construction begins with laying. In
constructing a nest, no new material is added. A nest bowl is made from materials
present in the cavity or nest box and by scratching an indentation.
Hooded merganser eggs are white and almost spherical. Eggs range in length
from 51.3 to 56.7 mm, in width from 42.5 to 45.4 mm, and in weight from 51.5 to 62.9 g.
They have disproportionately thicker shells compared to other species ofducks. Average
eggshell thickness (mean ? standard error) at the equator from 17 states is 0.576 ? 0.007
mm (White and Cromartie 1977).
Hens typically lay one egg every other day. Clutch size ranges from five to
twelve eggs (Baicich and Harrison 1997). Final clutch size may be considerably larger if
the nest is parasitized. After the clutch is nearly complete, down is plucked to line the
nest and cover the eggs. The female incubates for approximately 30 days. The male
leaves the female shortly after she begins incubation. The female incubates the eggs,
taking two to three breaks throughout the day. About 72 hours prior to hatching, chicks
begin tapping and peeping. Thirty to forty-eight hours before hatching, a star shaped
crack appears, and 12-24 hours before, the first hole appears. Within 24 hours of
hatching, chicks jump offthe nest and begin diving and feeding (Dugger et al. 1994).
Both intraspecific and interspecific nest parasitism are commonly found in nesting
hooded mergansers. Parasitism occurs when a female lays her eggs in the nest of
another. Hooded merganser hens will lay eggs in other hooded merganser nests
(intraspecific) and will also parasitize the nests ofwood ducks (interspecific). Also,
interspecific parasitism is common between hooded mergansers, common goldeneye
4
(Bucephala clangula) and common mergansers (Mergus merganser) where their breeding
range overlaps (Dugger et al. 1994).
Factors Influencing Reproductive Success
In a study completed on nest boxes at MCWMA in 1994 and 1995, hooded
mergansers were found to be using 21 % (15/73) ofavailable nest boxes. Their nest
success was 80% (12/15) and hatching success was 90% (151/168) (Willis 1996). Nest
success was determined by dividing the number ofsuccessful nests by the number ofnest
attempts. Hatching success was determined by dividing the number ofeggs hatched by
the number ofeggs laid. Both nest success and hatching success are proportions used to
determine overall reproductive success. Reproductive success is defined as the
proportion ofnests that successfully hatch at least one duckling (Dugger et al. 1994).
This study was used to determine the reproductive success ofhooded mergansers using
nest boxes at MCWMA and determine ifthere had been any changes from the 1994-1995
study to 1998. There are two factors that were considered in this study as possible
impacts on the reproductive success ofhooded mergansers using nest boxes at MCWMA,
organochlorine contamination and nest parasitism.
Use ofOrganochlorines
Organochlorines (OCs) were introduced commercially over 70 years ago as
pesticides and polychlorinated biphenyls (PCBs). They are hydrocarbons that have any
number ofhydrogen atoms replaced with chlorine atoms (Manahan 1994).
Organochlorines have similar properties. Because they are resistant to oxidation and
5
hydrolysis, OCs are persistent in the environment, remaining in soils and sediments years
after their use has discontinued (Bunce 1994).
Organochlorines are semi-volatile and can be transported great distances in the
atmosphere. They are removed from the atmosphere by wet or dry deposition. They
have relatively low solubility in water (Bunce 1994). Because they are non-polar, they
have a high affinity for sediments which are high in humic matter (Manahan 1997). Due
to their lipophilic nature, they have the ability to bioaccumulate in the fatty tissues of
individual organisms and biomagnify in the food chain. Bioaccumulation is the uptake
and concentration ofenvironmental chemicals by living systems. Itoccurs when an
organism has taken in, by diffusion or ingestion, a chemical, such as an organochlorine,
contained in sediment, soil, food, or water. Biomagnification refers to the passage of
chemicals up the food chain, from the herbivores to the carnivores or top predators
(Manahan 1997). As the chemical passes up the food chain the concentration increases.
The organochlorines ofinterest in this study were PCBs, DDT (1,1,1-trichloro 
2,2-bis-(p-chlorophenyl)ethane), DDE (l,1-dichloro-2,2-bis(p-chlorophenyl)ethylene),
aldrin (l,2,3,4,10,10-hexachloro-1 ,4,4a,5,8,8a-hexahydro-1,4-endo,exo-5,8 
dimethanonaphthalene), dieldrin (1,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a 
octahydro-1,4-endo,exo-5,8-dimethanonapthalene), heptachlor (l,4,5,6,7,8,8a 
heptachlor-3a,4,7,7a-tetrahydro-4,7-methanoindene), and heptachlor epoxide
(1,4,5,6,7,8,8a-heptachloro-2,3-epoxy-3a,4,7,7a-tetra-hydro-4,7-methanoindene). These
compounds were selected because they are some ofthe most common contaminants
found in ecosystems and are among the most widely studied organochlorines in aquatic
systems.
6
In 1929, PCBs were first commercially manufactured and sold in North America
under the tradename ofAroclor (Bunce 1994). The Aroclor products each carried a four
digit number in which the first two digits represent the 12 carbon atoms ofbiphenyl while
the percent by weight ofchlorine in the mixture was represented by the last two numbers
(Bunce 1994). By substituting one to ten chlorine atoms onto the biphenyl structure, 209
different PCB compounds can be formed (Manahan 1994). PCBs were produced for use
as dielectric fluids in power transformers and capacitors, plasticizers, de-inking fluids for
recycling newspapers, and in production ofnon-carbon copy paper (Bunce 1994). In
1966, PCB's were first noticed in wildlife and shortly thereafter found to be ubiquitous in
the environment (Bunce 1994). The manufacturing, processing and distribution ofPCB's
were banned in 1976 under the Toxic Substance Control Act (Manahan 1994). The
continued use ofPCB containing transformers and disposal ofPCB waste are two
important sources ofcontinued contamination today.
In 1939, Paul Muller discovered DDT's capability as an insecticide (US PHS
1992 a). DDT was sprayed during World War II in the jungles ofthe Pacific islands and
Asia in order to prevent insect-borne diseases such as typhus and malaria (Bunce 1994).
Besides being used against typhus and malaria, DDT was used all over the world
agriculturally to control insects (Bunce 1994). Its agricultural use thrived because it was
cheap, effective, had a low acute toxicity to mammals, and was persistent (Bunce 1994).
DDT gets into bodies ofwater by direct spraying for insects over open waters, from
wastes ofDDT producers, or with its metabolites, DDE and DDD, through runofffrom
contaminated soils. In 1972, the EPA banned the use ofDDT, except in cases ofpublic
7
health emergencies. Itis still produced and used in some Central and South American
countries and in India (US PHS 1992 a).
Aldrin and Dieldrin are two structurally similar synthetic compounds used as
insecticides. In 1948, aldrin was first introduced as a pesticide (US EPA 1986 a). Once
in the environment, sunlight and bacteria readily convert aldrin into dieldrin. For this
reason, dieldrin is predominantly found in the environment. These two compounds were
primarily used to control com pests (by treating the soil) and in the citrus industry from
1950 until 1970. Other uses ofdieldrin and aldrin included; general crop protection from
insects, timber preservation, and termite proofing ofplastic and rubber coverings of
electrical and telecommunication cables, plywood and building boards. The EPA
cancelled all uses ofthe compounds, except as a termiticide, in 1974, although this use
has since been cancelled also (US PHS 1992 b).
In 1952, heptachlor was registered for use as an insecticide in the United States.
From 1953 to 1974, heptachlor was applied extensively to soil and seeds to protect com,
small grains, and sorghum from pests. In both cultivated and uncultivated soils it was
used to control ants, cutworms, maggots, termites, thrips, weevils, and wireworms.
Nonagriculturally, it was also used to control termites and household insects. Heptachlor
is broken down to the more toxic heptachlor epoxide in the body ofanimals and in the
environment by bacteria. Both compounds enter surface water from waste discharges of
facilities producing heptachlor and from runoffoftreated soils. Heptachlor is also a
component ofthe pesticide cWordane and can enter the surface water by the same means
(US EPA 1986 b). The EPA cancelled most registered uses ofheptacWor in 1974, and as
of 1988, sale, distribution, and shipment ofheptachlor products were prohibited in the
8
United States. Currently, heptachlor is only permitted to be used commercially for the
control offire ants in power transformers (US PHS 1992 c).
Organochlorine Impacts on Birds
Ten to twenty years after their initial use, OC residues were discovered in
wildlife. Some ofthe first records ofOC residues in wildlife were in birds (Barnett 1950,
Mitchell et al. 1953). One ofthe earliest studies looked at the effects ofinsecticides on
game birds, after several reports ofdead pheasants in apple orchards in Washington came
out. Besides acute fatal toxicity at high concentrations, DDT was found to cause
symptoms such as tremors, paralysis, and erratic flight (Barnett 1950). Another early
study focused on the concentration ofDDT in the food source ofaffected birds,
earthworms (Lumbricus terrestris). Shortly after American elms (Ulmus americana)
were sprayed for Dutch elm disease on the University ofIllinois campus, dead and dying
American robins (Turdus migratorius) were found. Earthworms were concentrating
DDT and its metabolite DDE mainly in their crop and gizzard from feeding on leaflitter
which had been sprayed. The robins would feed on the contaminated worms, as well as
feed them to their nestlings. This resulted in tremors and eventually death to the robins
(Barker 1958).
Barkers study led to more studies involving different species at various levels of
the ecosystem. OCs were soon found in many different ecosystems and biota with the
highest concentrations in top predators (Hunt and Bischoff 1960, Meeks 1968, Korschgen
1970, Niethammer et al. 1984). Chlorine-36 ring-labeled DDT was applied to a marsh
and traced through an entire wetland system; water, phytoplankton, sediments, aquatic
plants, invertebrates, fish, amphibians, reptiles, birds, and mammals. Concentrations of
9
raried at each level depending on diet but in general concentrations tended to
;e up the food chain (Meeks 1968). Niethammer et al. (1984) found similar results
ow lakes in northeastern Louisiana. Tertiary consumers (top predators) tended to
igher concentrations ofOC residues and primary consumers (herbivores) had the
levels.
Today, OCs are still ofconcern due to the great impact they have on various bird
ltions, especially top predators. Impacts are mainly on eggshell thickness and
uction. For example, DDT and its metabolites inhibit calcium deposition in avian
s by inhibiting the production ofthe enzyme, carbonic anhydrase (Friend and
:r 1970). Carbonic anhydrase is the enzyme which makes calcium from the
;tream available to the oviduct for deposition ofthe eggshell (Peakall 1970). By
:ing this enzyme, resulting eggshells are often too thin to withstand the weight ofan
lting adult (Molholt 1994). Several field studies ofDDT and DDE found a high
nce ofcracked eggs and eggshell thinning in different species ofbirds (Ohlendorf
[985, Henny et al. 1984, Kiffet al. 1979, Hickey and Anderson 1968). In black-
ed night-herons, Nyetieorax nyetieorax, when levels ofDDE exceeded only 8 ppm
, the incidence ofcracked eggs increased, resulting in smaller clutch sizes (Henny
[984). To confirm the relationship ofDDT and eggshell thinning, studies have
lone comparing eggshell thickness prior to and after the widespread use ofOCs. In
eggshell thicknesses ofcommon and red-breasted mergansers (Mergus serrator)
;ompared to pre-1947 museum collections. Eggshells ofboth species were found to
nificantly thinner in 1977 compared to before 1947, (23.5% and 17.7%
:tive1y) (White and Cromartie 1977).
10
lues are declines
ebeker et al. 1992,
ltions of
leo sparverius)
week (Henny et
nallards (Anas
~metatarsus) and
~ dieldrin than
ctural
with OC residu~s,
~andible was
~se behavioral
I
I
11978, Haegele
ontaminated site
:rred to nests built
!l nest
Inated with a
!
~ compared to 14
lS causing a
~bryonic
~es (Streptopelia
n doves fed DDE.
11
Males spent less time on activities such as nest site selection, wing-flipping, preening,
and bow-cooing (Haegele and Hudson 1977).
Susceptibility ofHooded Mergansers
Hooded mergansers are top aquatic predators that consume mostly fish,
crustaceans, and aquatic insects (Dugger et al. 1994). Due to the ability oftheir prey to
bioaccumulate contaminants, hooded mergansers are at risk ofreceiving relatively high
doses oforganochlorines from their food sources (White and Cromartie 1977). Previous
studies have investigated organochlorine residues and eggshell thinning in hooded
mergansers, as well as in common and red-breasted mergansers. These studies have been
conducted in New York, Maine, New Hampshire, Vermont, Michigan, Iowa, North
Dakota, Arkansas, Missouri, Tennessee, and Minnesota (Table 1) (White and Cromartie
1977, Zicus et al. 1988). These states were divided into three regions: northeast, mid 
west, and south central. The lowest levels oforganochlorine residues and thickest
eggshells were found in the south central region. The highest levels oforganochlorine
residues and thinnest eggshells occurred in the northeast. Eggshells were found to be
8.3% thinner in a study from 1973-1975 (White and Cromartie 1977) ofhooded
mergansers from 10 different states than in pre-1927 museum collections. In a 1981
study, eggshells were found to be 9.6% thinner in Minnesota than in years prior to DDT
use (Zicus et al. 1988).
No studies were found that examined the impact ofOCs on hooded mergansers
and their eggshell thickness in Ohio. In this study I attempted to determine how hooded
mergansers nesting in Ohio compare to the previously mentioned studies in other states.
12
Table 1. Hooded merganser eggshell thickness comparisons (mean ? standard error) from
previous studies and historical collections. A decrease in eggshell thickness is shown
from the pre-DC era, through DC use, and after most DCs were banned in the late 1970's.
Sample Size
OCTime Date Thickness (#clutches/ Location Source
Period (mm) #eggs)
White and
Pre-DC 1880-1927 0.628?0.025 6/55 lA, MI, Comartie,
MN,ND, 1977
WI
Faber and
During use Pre-1947 0.614?0.009 ?/44 WI Hickey,
1973
Faber and
During use 1970 0.599?0.017 ?/11 WI Hickey,
1973
White and
During use 1973-1975 0.576?0.005 28/174 lA, MI, Comartie,
MN,ND, 1977
WI
Post DC 1981 0.568?0.007 21/70 MN Zicus et aI.
1988
13
Occurrence ofNest Parasitism
Nest parasitism, also called brood parasitism, occurs when a hen lays her eggs in
the nest ofanother. When they are laid in the nest ofthe same species it is called
intraspecific nest parasitism. When eggs are laid in the nest ofa different species it is
called interspecific nest parasitism. Nest parasitism, both intraspecific and interspecific,
is a common occurrence in cavity nesting waterfowl such as hooded merganser, wood
duck, and common goldeneye (Morse et al. 1969, Semel et al. 1988, Andersson and
Eriksson 1982, Bouvier 1974).
Nest parasitism appears to impact reproductive success ofwaterfowl using nest
boxes. At Max McGraw Wildlife Foundation, Illinois, a significant decrease was found
in hatching success between 1976 and 1987 in wood ducks using nest boxes. A
significant increase in intraspecific nest parasitism was inversely correlated with the
decrease in hatching success (Semel et al. 1988). In natural conditions, such as tree
cavities, normally parasitism tends to be less frequent and hatching success tends to be
greater. Bellrose and Holm (1994) found hatching success to be 94% and intraspecific
nest parasitism to be 12% for wood ducks in natural nest cavities. In comparison, the
hatching success ofwood ducks using nest boxes at MCWMA was 86% and intraspecific
nest parasitism was 98% (Willis 1996). Interspecific nest parasitism also tends to have
an impact on reproductive success. Doty et al. (1984) found a decrease in hooded
merganser and wood duck nest success in nests where interspecific nest parasitism (what
they called dual nests) occurred. Hooded merganser nest success was 73%, wood duck
nest success was 79%, and dual nest success was 65%.
14
A possible explanation for the increase in nest parasitism in waterfowl using man
made nest boxes may be the density and visibility ofthe nest boxes. Semel et al. (1988)
tested this by comparing wood duck nests that were visibly isolated, visibly clumped, and
well-hidden. Hatching success ofwell-hidden nests was 82.0% and visibly isolated and
visibly clumped nests were 73.7% and 74.1 %, respectively. Parasitism was only 30% in
well-hidden nests and 50% for visibly isolated and clumped nests, combined. Overall the
study showed that hatching success was inversely correlated with population density,
frequency ofparasitism, and clutch size. Some ofthe negative impacts found due to
parasitism were nest abandonment, damaged eggs, and eggs laid after incubation began
(Semel et al. 1988).
In 1994-1995, intraspecific nest parasitism ofhooded mergansers nesting at
MCWMA was only 13% (2/15) and interspecific nest parasitism by wood ducks was
80% (12/15) (Willis 1996). This study attempted to determine ifthere had been a change
in nest parasitism ofhooded merganser using nest boxes at MCWMA and ifthere was an
impact on their reproductive success.
15
METHODS
Null Hypotheses
This study was designed to test the following null hypotheses:
1. Eggshell thicknesses ofhooded merganser at Mosquito Creek Wildlife
Management Area do not differ from eggshell thicknesses ofhistorical
collections.
2. Eggshell thicknesses ofhooded mergansers at MCWMA do not differ from
eggshell thicknesses ofprevious studies.
3. The reproductive success in the hooded merganser from this study does not
differ from the reproductive success in 1994 and 1995 at MCWMA
4. Eggshell thickness does not correlate with reproductive success ofhooded
mergansers at MCWMA.
5. Organochlorine concentrations ofhooded mergansers at MCWMA are not
greater than concentrations from previous studies.
Study Site
I conducted this study on Eagle Marsh and Wood Duck Marsh at Mosquito Creek
Wildlife Management Area in Trumbull County, Ohio (Fig. 1). The northern tip ofthe
Mosquito Creek Reservoir is located in the wildlife management area. The rest ofthe
reservoir extends south into Mosquito Creek State Park between State Route 88 and 305.
The West side ofEagle Marsh, which is divided by North Park Avenue, is 13 ha in size
and contained nine nest boxes (Fig. 2). Wood Duck Marsh, which is located on State
Figure 1. Location ofstudy site at Mosquito Creek Wildlife Management Area in
Trumbull County, Ohio.
Mosquito Creek Wildlife Management Area
Trumbull County
17
Figure 2. Location ofnest boxes used for this study at Eagle and Wood Duck
Marsh.
'115
~/~
'Ill fll
II"
lft4 Ii:
19
20
Route 87, approximately one mile east ofState Route 45, is 113 ha in size and contained
approximately 58 nest boxes, 40 ofwhich were used in this study (Fig. 2). The majority
ofthe nest boxes are old fiberglass water softener cylinders placed 1 to 2 m directly
above the surface ofthe water on predator proofposts. A few nest boxes consist ofold
metal rocket boxes, which are aluminum cylindrical structures with a pointed top. I
selected these study sites for two reasons: (1) at least 20 pairs ofhooded mergansers were
known to use these nest boxes in the past five years (Willis 1996 and ODNR-DOW nest
records 1992-1996), and (2) close proximity to Youngstown State University allowed for
intensive nest box checks.
Behavioral Observations
From February 26 until March 22, 1998, I made behavioral observations on Eagle
Marsh. Every other morning from 0700 until 0930 h, I recorded visits to nest boxes by
hooded mergansers and wood ducks. These observations were made in order to
document first nesting attempts ofthe season by hooded mergansers and by wood ducks.
Observations were made from my vehicle parked on North Park Avenue using a spotting
scope and binoculars.
Nest Box Checks
Permits were obtained from the US Fish and Wildlife Service and the Ohio
Department ofNatural Resources (ODNR), Division ofWildlife to conduct research at
MCWMA. Beginning on March 24, 1998, I monitored the nesting activities ofhooded
mergansers and wood ducks. Johnboats provided by Ohio Department ofNatural
21
Resources, Division ofWildlife (ODNR-DOW), and a canoe provided by YSU
Department ofBiology were used to access nest boxes. I checked nest boxes after 1200
h, in order to avoid disturbing females during the egg-laying stage. Itgenerally took one
hour to check nest boxes on Eagle Marsh and three hours to check nest boxes on Wood
Duck Marsh. During each nest visit, I recorded the number ofhooded merganser eggs
and wood duck eggs. I numbered each egg from each species with a Sharpie marker on
the blunt end ofthe egg before placing it back in a box. Ifeggs from both species were
present in the same box, I numbered them separately. I measured the length and width of
all hooded merganser eggs with Mitutoyo calipers to the nearest 0.02 mm and weighed
them with a Pesola scale to the nearest 0.5 g. Once a female began incubating, her nest
box was not checked for three weeks in order to minimize the risk ofabandonment.
After three weeks, I visited each nest box to record final clutch size in order to estimate
hatching success.
Collection ofSamples
I randomly removed two unincubated hooded merganser eggs (Zicus et al. 1988)
from each active hooded merganser nest, one egg per nest visit. One egg was removed
early in the egg laying stages and one late in the laying stage in order to minimize bias
towards either end ofthe laying period. Active hooded merganser nests contained at least
five hooded merganser eggs that were laid at a rate ofone egg per two days. Any
parasitic hooded merganser eggs were removed from active wood duck nests after seven
wood duck eggs were laid. Abandoned hooded merganser eggs were also collected from
nest boxes. A previously active nest was considered to be abandoned ifa full clutch,
22
between five and twelve eggs, had been laid but never incubated. Abandoned eggs were
collected during the first week ofMay in order to allow another hen to nest in the box.
Three entire clutches were removed from three different nest boxes to account for within
clutch variation (Zicus et al. 1988). One clutch from Eagle Marsh, containing 12 eggs,
was removed from an abandoned hooded merganser nest that was parasitized by at least
one other hooded merganser hen. The other two clutches were collected from Wood
Duck Marsh. The first clutch, containing 10 eggs, was removed from an active wood
duck nest, which was being parasitized by at least one hooded merganser hen. The
second clutch removed was from an abandoned nest, which contained 12 eggs, and was
also parasitized by at least one hooded merganser hen. Five eggs were collected from a
drop nest as well. A drop nest is a nest containing less than five eggs that was never
incubated. All collected eggs were stored at 5?C until further analysis.
Water and sediment samples were collected from four random locations on Wood
Duck Marsh on July 7, 1998 (Fig. 3). Samples were collected from Eagle Marsh at three
random locations on September 1, 1998 (Fig. 3). Water samples were collected in pre 
cleaned 4-L amber solvent jugs. One 4-Ljug was filled per sample location. Water
samples were stored at ?5C until further work up. Sediment samples were collected at
the same locations as the water samples using a core-sampling device. Core samples
were frozen upright at -15?C in plastic tubes until extraction and work-up.
Egg Analysis
Prior to processing each egg, I remeasured its length, width, and weight and
measured the volume by water displacement (White and Cromartie 1977). I cut each egg
Figure 3. Topographic map ofstudy site at MCWMA. Numbers on each pond
indicate the location ofwater and sediment samples.
24
/
/
L.::'1
~l
A_ ',1
<'70 r'.C'> . ' :'UI '",":", .
. 7' .o I
. ~,)'lt I
25
open near the equator with a scalpel, placed the contents in a four-ounce pre-cleaned jar,
and froze it at -15?C until analysis. Eggshells with membranes were air dried at room
temperature for at least 30 days (White and Cromartie 1977). Using a Starrett T216RL
micrometer with ball attachments, eggshell thickness was measured to the nearest 0.001
inch at three random spots near the equator to obtain a mean thickness. The mean
thickness in inches was then converted to mm. The eggshells were also weighed using a
Denver Instruments M 120 scale measuring to 0.0001 g.
Egg contents were homogenized with a Brinkmann Homogenizer. Four to 9 eggs
were pooled together based on eggshell thickness, which resulted in 12 samples (A-L).
Approximately 5 g ofeach egg were pooled together and approximately 109 ofthe pool
were removed for work-up. Sodium sulfate was mixed with the 109 sample to dry the
egg and spiked with 50 J.!L ofd6-aHCH (deuterated alpha-hexachlorocyclohexane)
(O.lng/J.!L). The egg was then placed in a pre-cleaned cellulose thimble and Soxhlet
extracted for 7 h in dichloromethane (White and Cromartie 1977). The extract was
reduced to 10 mL using rotary evaporation.
Prior to placing the 10 mL sample on a clean-up column, % lipid was determined
for each ofthe 12 samples. One mL ofthe sample was placed in a pre-cleaned beaker,
weighed, and left out to air dry over night (approximately 24 h). The beaker was
reweighed the next day. Percent lipid was determined using the calculation found in
Appendix B from Patuxant Wildlife Research Center.
A clean-up column, to remove lipids, used 15 g Florisil (2% water added) topped
with approximately halfan inch ofSodium Sulfate. The column was cleaned with 45 mL
ofhexane. The 10 mL sample was placed on the column and eluted 6 mL of6% ethyl
26
ether in hexane. The sample was reduced and solvent exchanged into 1 mL ofiso-octane
under a gentle stream ofnitrogen.
Blanks and duplicates were run with every other set ofsamples as quality
assurance and went through the same work up as samples.
Six organic chicken eggs were used as quality control to make sure the procedure
for extraction worked. Three were spiked with 100J.1L ofa pesticide mixture (20ng/J.1L
for each pesticide) and three were spiked with 100J.1L ofAroclor 1268 (lO.5ng/J.1L).
These controls went through the same work up as samples.
Water Analysis
Each water sample was filtered through a 47 mm Whatman glass fiber filter
(grade ODIUM) to remove suspended organic matter. Filters were cleaned by baking in
a Thermolyne Muffle Furnace at 450?C for 24 h and individually stored in pre-cleaned
aluminum foil. Each ofthe 4-L water samples were spiked with 10 J.1L ofPCB 103 (729
ng/J.1L). Water samples were placed in a pre-cleaned stainless steel canister which was
pressurized by nitrogen to force the water through the filter. The filtered water was
extracted with a Varian 1 g Mega BondElut C8 solid phase extraction cartridge, to
collect the organochlorine compounds. The volume ofthe water extracted was measured
and cartridges were wrapped in aluminum foil, sealed in plastic bags, and stored at -15?C.
Before extraction, cartridges were allowed to thaw for approximately an hour.
Ten mL ofhexanes were pushed through the cartridge, reduced and solvent exchanged
into 2 mL ofiso-octane under a gentle stream ofnitrogen. A clean-up and fractionation
column was made with 3 g Silicic Acid (3% water added) followed by 2 g Alumina (6%
27
water added) and topped with approximately an inch ofSodium Sulfate. The column was
cleaned with 30 mL ofdichloromethane (DCM) and 30 mL ofpetroleum-ether (PE). The
sample was placed on the column and eluted in two fractions. Fraction 1 (F1) was eluted
with 30 mL PE and contained PCBs and some DDE. Fraction 2 (F2) was eluted with 30
mL DCM and contained the remaining OC pesticides. Both fractions were reduced and
exchanged into 2 mL iso-octane with nitrogen. 200 JlL were removed from F2 and stored
in microvials for analysis ofheptachlor epoxide and dieldrin. The remaining F2 and all F1
were cleaned with 1 mL sulfuric acid before analysis.
Blanks and duplicates were run with every other set ofsamples as quality
assurance and went through the same work up as samples.
Sediment Analysis
Core samples were removed from the freezer and water was run over the surface
ofthe plastic tube for approximately five min to loosen the sediment. Layers were sliced
into sections approximately 10 rom thick using a circular saw with a pre-cleaned carbide
blade. Slices were placed into pre-cleaned sixteen-ounce jars and placed back in the
freezer until work-up.
Sediment samples were freeze dried for approximately 4 days and weighed.
Dried sediment was placed directly in cellulose thimbles and Soxhlet extracted for at
least 12 h in DCM. The extracted sample was reduced to 10 mL using rotary evaporation
and cleaned using the Florisil column described above. The sample was reduced and
solvent exchanged into 1 mL ofiso-octane using nitrogen.
28
Blanks and duplicates were run with every other set ofsamples as quality
assurance and went through the same work up as samples.
GC Analysis
Quantitative analysis was carried out with a GC Varian Star 3400CXgas
chromatograph equipped with an electron capture detector (GC-ECD) using a DB-5
column (60 m, 0.25 mm i.d., 0.25 !lm film thickness; J&W Scientific). Samples were
injected splitless (split opened after 1.0 min) at an initial temperature of90?C. After a 1 
min hold, the oven was ramped at 10 ?c min-I to 160?C, 2 ?c min-I to 240?C, 20?C min 
I to 270?C, and held for 10 min. Injector and detector temperatures were 250?C and 300
?c, respectively. The carrier gas was hydrogen at 60 cm S-I. Samples were quantified
versus 4-8 standards that spanned a 1000-fold concentration range.
Statistical Analysis
I estimated the reproductive success ofhooded mergansers at Eagle Marsh and
Wood Duck Marsh. Reproductive success is the proportion ofnests that successfully
hatch at least one duckling (Dugger et al. 1994). Data from each successful nest was
used to calculate means and standard error (SE) for total clutch laid, clutch size at hatch,
and number ofducklings leaving the nest (Zar 1996). From this data proportionate
measures were also calculated: nest box use (number nest attempts/ number ofboxes
available), nest success (number ofsuccessful nests/ number ofnest attempts), hatching
success (number ofeggs hatched! number ofeggs laid), nest abandonment (number of
nests abandoned! number nest attempts) and nest predation (number ofnests predated!
29
number ofnest attempts). Intraspecific and interspecific nest parasitism for both hooded
merganser and wood ducks was calculated. Data from drop nests were not used in any
reproductive success calculations. Only eggs present in the nest box at the time of
hatching were used to calculate hatching success. Two-way contingency tables were
used to compare reproductive success ofhooded mergansers between this study and a
1994-1995 study (Willis 1996 and Zar 1996).
I also estimated reproductive success and intraspecific and interspecific nest
parasitism ofwood ducks nesting at MCWMA using the proportionate measures above.
Two-way contingency tables were used to compare reproductive success ofwood ducks
between this study and a 1994-1995 study (Willis 1996 and Zar 1996).
Means and standard errors (SE) were calculated for egg length, egg weight, egg
mass, eggshell weight, eggshell thickness, and the Ratcliffe thickness index (Zar 1996).
The Ratcliffe thickness index is used to determine eggshell thickness while taking
variation ofegg size into account (Ratcliffe 1967). Itis calculated by dividing the weight
ofthe eggshell (mg) by the product ofthe length and width ofthe egg (Ratcliffe 1967).
To correlate hooded merganser reproductive success with mean eggshell thicknesses, the
Spearman's rank correlation was used (SPSS 1998).
30
RESULTS
Behavioral Observations
At least one pair ofhooded mergansers was at Eagle Marsh on the first day of
observations, February 26, 1998. I observed the female ofthe pair checking one nest box
for approximately 2 min. Approximately a week later another pair was spotted on the
pond along with 3 single males. By March 15, there were at least 17 hooded mergansers
on Eagle Marsh. Nest box checking was not observed by hooded mergansers again until
March 7 and 17. After March 17 nest box checking by hooded mergansers was observed
regularly.
The first pair ofwood ducks was observed on Eagle Marsh on March 7,1998. I
observed the male ofthis pair checking a nest box. He appeared to be trying to get the
female to go into the box he had checked by displaying, circling, and looking at the nest
box. Wood ducks were not observed checking nest boxes again until March 17. After
that date only females were observed entering the nest boxes.
Laying Chronology
Female hooded mergansers began laying eggs at Mosquito Creek Wildlife
Management Area approximately March 24, 1998. Seven eggs were found in a single
nest box on Wood Duck Marsh with the first box check. Nest boxes were checked for 78
days, from 24 March to 9 June 1998. The first wood duck egg was found on Eagle Marsh
on March 26. Mergansers had a peak oflaying during the first ten days ofnest box
checks and a second peak around day thirty (Fig. 4). Wood ducks had one peak around
Figure 4. Chronology ofhooded merganser egg laying at MCWMA. Time 1 =
March 24, when first eggs were found. Each block represents 10 days with the
first block starting at 1.
~-- ---_._---- --~
100~....
S 80
c:I:.l
~ 60
~ Q)
i 4020
~ 0
:u: 0
1 2 3 4 5 6 7 8 9
Laying time
32
33
day thirty, which gradually tapered off(Fig. 5). The last recorded hooded merganser egg
was laid approximately 15 May 1998 and the last wood duck egg was laid approximately
30 May 1998. There was a total of258 hooded merganser eggs laid and 594 wood duck
eggs laid. Ofthe 258 hooded merganser eggs, 243 (94%) were used to determine the
laying chronology. To determine wood duck laying chronology, 532 of594 (90%) eggs
were used. Eggs laid during the three week incubation period, when nests were not
checked, were not used to determine laying chronology.
Egg Parameters
During the study, hooded merganser eggs were measured in 30 nest boxes and
were collected from 25 ofthose boxes. On average, two eggs were removed from each of
those 25 nests. One dump nest was collected that contained 5 eggs. Three full clutches
were removed from three different nests. Two clutches were removed from abandoned
nests and the other was removed from a wood duck nest that was being parasitized by at
least one hooded merganser hen (10 total eggs). One ofthe abandoned nests was
collected from Wood Duck Marsh (12 eggs) and the other was collected from Eagle
Marsh (12 eggs). Parasitic hooded merganser eggs found in wood duck nests were also
collected.
Of258 hooded merganser eggs laid during this study, field data was recorded for
238 eggs (length, width, and mass). Eggs that were laid during the three week incubation
period were not measured. There were also additional eggs that inadvertently did not
have any measurements recorded. The mean length and SE was 54.1?0.1 mm (range:
50.54 - 59.78 mm). The mean width and SE was 44.l?0.1 mm (range: 41.15 - 47.93
Figure 5. Chronology ofwood duck egg laying at MCWMA. Time 1 = March 24
when first when first eggs were found. Each block represents 10 days with the
first block starting at 1.
~ 250.-
S 200
~ bJ)
150bJ)Q)
~ 100
~ 50
~ 0
=It 0
1 2 3 4 5 6 7 8 9
Laying time
35
36
mm). The mean mass and SE was 61.6?0.3 grams (range: 46.5 - 84.0 g) (Appendix A,
Table 6).
Eighty-three eggs were collected and used in lab analysis. The means and SE for
those 83 eggs include; 54.1?0.2 mm in length, 44.3?0.1 mm in width, 62.5?0.5 gin
mass, 9.76?0.08 g in eggshell mass, 0.605?0.004 mm in eggshell thickness, and a
Ratcliffe Index of4.069?0.028 (Appendix A, Table 6 and 7). Eggshell mass ranged from
6.8855 - 11.4362 g. Eggshell thickness ranged from 0.483 - 0.669 mm. The Ratcliffe
Index ranged from 3.083 - 4.589.
Of14 represented clutches, 9 ofthose nests were successful. Spearman's rank
correlation was used to determine ifthere was a correlation between reproductive success
ofhooded mergansers and eggshell thickness (Figure 6). The correlation coefficient (rs)
was 0.444 and found not to be significant (SPSS 1998).
Nest Box Summaries
During this study, hooded mergansers attempted to use 16 ofthe 49 available nest
boxes (33%) at Eagle Marsh and Wood Duck Marsh which appeared to be an increase
from 1994-95 (21 %) (Willis 1996). Eleven nests were successful (69%) and hatched at
least one duckling. This appeared to be a slight decrease in nest success from 1994-95 at
80% (Willis 1996). There was a significant decrease in hatch success from 90% in 1994 
95 (Willis 1996) to 79 % (116/147) in 1998 (P <0.05). Two nests were abandoned (13%)
after 12 eggs had been laid. One nest was predated (6%) after 11 eggs had been laid.
Two additional nest attempts were made in nest boxes where wood ducks had already
started a nest. The two nest boxes were located next to each other. Both hooded
Figure 6. Correlation between reproductive success ofhooded mergansers and
eggshell thickness at MCWMA. Reproductive success was determined from the
% ducklings that hatched in successful nests (# eggs hatched/# eggs laid). The
correlation coefficient (rs) was 0.444, P=0.232 (SPSS 1998).
1.2
1 ??
""CS ? ? ?
~
~ 0.8
~-=
\0.6 ?
rI.l
~
~ 0.4
~ ?=
0.2
0
0.56 0.58 0.6 0.62 0.64 0.66 0.68
eggshell thickness (mm)
38
39
merganser and wood duck hens laid full clutches in both ofthese boxes. Both, however,
were initiated and incubated by a wood duck. Only one drop nest was recorded during
this study, which contained 5 eggs. A summary ofnest box activities can be found in
Table 2. A summary ofthe fate ofnests can be found in Table 9 (Appendix A).
Clutch size for successful hooded merganser nests was 15.1?1.5 (mean?SE). For
non-parasitized and parasitized successful nests, clutch sizes were 1O.5?1.9 and 17.7?1.2,
respectively. Mean and SE for clutch size at time ofhatch in successful nests was
13.4?1.3. Clutch sizes at time ofhatch for non-parasitized and parasitized nests were
9.3?1.7 and 15.7?1.2, respectively. The mean and SE for number ofducklings leaving
successful nests was 10.5?1.2. In non-parasitic and parasitic successful nests the mean
number ofeggs hatched were 7.0?0.9 and 12.6?1.3 (mean?SE), respectively. A
summary ofmeans and SE ofhooded merganser nesting activities in successful nests can
be found in Table 3.
The first hooded merganser clutch hatched on May 8, 1998. Twelve chicks were
observed in nest box 390 on that visit. Box 389 may have hatched offa day or two
earlier than that. On May 8, there were only 5 unhatched eggs and one dead chick out of
20 eggs left in box 389. Only one clutch had not hatched by June 7, 1998. By final box
inspection on July 1, all clutches had hatched.
Wood ducks attempted to use 37 ofthe 49 available nest boxes (76%) at Eagle
Marsh and Wood Duck Marsh, which was an increase from 1994-95 (64%) (Willis
1996). Nineteen nests were successful (24%) and hatched at least one duckling in 1998.
This appeared to be a decrease in successful nests from 1994-95 (47%) (Willis 1996).
Hatch success also appeared to slightly decrease from 86% in 1994-95 (Willis 1996) to
40
Table 2. Summary ofhooded merganser nest box activity at MCWMA. The data from
this study was compared to a study done in 1994 and 1995 on the same ponds using 2x2
contingency tables (Willis 1996).
1994-1995 1998 *p
% Nest box use 21 (15/73) 33 (16/49) NS
% Nest success 80 (12/15) 69 (11/16) NS
% Hatch success 90 (151/168) 79 (116/147) <0.05
*Chi square analysis
NS = not significant
41
Table 3. Summary ofmeans and standard error ofsuccessful hooded merganser nests at
MCWMA. Means and standard error are also shown for parasitized (intraspecific) and
non-parasitized hooded merganser nests for comparison.
Means
Parasitic eggs in
successful nest boxes
Clutch size for all eggs
laid in successful nest
boxes
Clutch size for eggs in
successful nests prior to
hatch
Number ofducklings
leaving nests
All successful
nests
4.2?1.4
15.1?1.5
13.4?1.3
1O.5?1.2
Non-parasitized
nests
1O.5?1.9
9.3?1.7
7.O?O.9
Parasitized
nests
17.7?1.2
15.7?1.2
12.6?1.3
42
81% (261/324) in 1998. Eight nests were abandoned (22%) and ten nests were predated
(27%). There were no drop nests found for wood ducks during this study. A summary of
wood duck nest box activities can be found in Table 4.
One wood duck clutch hatched around May 16. Ten unhatched eggs out of24
were found in a box on Eagle Marsh during that visit. Several wood duck clutches
continued to hatch after June 7.
Parasitism
The mean number ofparasitic hooded merganser eggs laid in all successful nests
was 4.2?1.4 (mean?SE). In the 7 parasitized nests the mean number ofparasitic hooded
merganser eggs was 6.6?1.5. Intraspecific nest parasitism in successful nests for hooded
mergansers significantly increased from 13% in 1994-95 (Willis 1996) to 75% (12/16) in
1998. However, interspecific nest parasitism in successful hooded merganser nests by
wood ducks significantly decreased from 80% in 1994-95 (Willis 1996) to 44% (7/16) in
1998 (Figure 7). Interspecific nest parasitism in successful wood duck nests by hooded
mergansers was 43% (16/37). That was a significant decrease from 98% in 1994-95
(Willis 1996). Intraspecific nest parasitism for successful wood duck nests did not appear
to change from 1994-95 (47%) (Willis 1996) to 1998 (43%). Intraspecific and
interspecific nest parasitism ofhooded mergansers and wood ducks is summarized in
Table 5.
43
Table 4. Summary ofwood duck nest box activity at MCWMA. The data from this study
was compared to a study done in 1994 and 1995 on the same ponds using 2x2
contingency tables (Willis 1996).
1994-1995 1998 *p
% Nest box use 64 (47/73) 76 (37/49) NS
% Nest success 47 (22/47) 24 (19/37) NS
% Hatch success 86 (249/290) 81 (261/324) NS
*Chi square analysis
NS = not significant
Figure 7. Interspecific nest parasitism ofan active hooded merganser nest at
MCWMA. Hooded merganser eggs are white, considerably larger, and more
spherical than wood duck eggs, which are beige, smaller, and more elliptical.
45
46
Table 5. Intraspecific and interspecific nest parasitism summaries ofhooded merganser
and wood ducks at MCWMA. The data from this study was compared to a study done in
1994 and 1995 on the same ponds using 2x2 contingency tables (Willis 1996).
% Hooded merganser
nests parasitized by...
Wood duck
Hooded merganser
% Wood duck
nests parasitized by...
Wood duck
Hooded merganser
*Chi square analysis
NS =not significant
1994-1995
80 (12/15)
13 (2/15)
98 (46/47)
47 (28/60)
1998
44 (7/16)
75 (12/16)
43 (16/37)
43 (16/37)
*p
<0.05
<0.05
<0.05
NS
47
Lab/GC Analysis
Egg, water and sediment samples were worked up in the lab according to the
methods mentioned previously. The percent lipid determination for 83 collected eggs
was 15.88 ? 0.17 (mean?SE). No results were obtained on organocWorine
concentrations in egg, water, or sediment samples. Organochlorine spikes in all ofthe
samples, duplicates and controls were not recovered either. The methods I used in the lab
may have been incorrect, particularly the clean-up column. Although, it is assumed that
there were Des in samples, the failure ofspiked controls to give results shows the
methods did not work. In the future, different methods should be tried to find a
successful way.
48
DISCUSSION
Laying Chronology
Hooded merganser hens began laying approximately March 24 at MCWMA.
This is consistent with most documented studies, where nest initiation usually begins
between February and April, depending on latitude (Dugger et al. 1994). Maryland and
Indiana, near the same latitude as Ohio, reported similar findings for nest initiation
between March 13 and 24 (McGilvrey 1966, Mumford 1952).
Itappears as though the laying chronology for hooded mergansers nesting at
MCWMA is typical. Nest initiation and peak laying times appear to correspond with
studies done on hooded mergansers in other parts ofthe country. Two peaks were
observed in hooded merganser laying at MCWMA. One was found during the first ten
days oflaying and another approximately 20 days later. This trend was also noticed in a
study in Western Oregon, where a peak in laying was found during the first week ofnest
starts and again approximately 3 weeks later. These two separate peaks may indicate two
different age groups ofhens (Morse et al. 1969). Older, more experienced hens may
begin laying very early and younger, less experienced hens may begin laying later.
Adding to the second peak may also be renesting attempts. Hooded merganser hens that
may have been unsuccessful on their first attempt will usually attempt to renest.
Wood Duck laying chronology also appears to be typical compared to a 1994-95
study conducted at the same study site (Willis 1996). The first wood duck eggs were
found in my study on March 26 and the first eggs were found in 1994-95 around March
28. A peak in laying was also found during the first week oflaying in 1994-95.
49
Egg Parameters
Hooded merganser eggs at MCWMA appeared to be slightly larger than studies
reported in Missouri and South Carolina. Kennamer (1988) reported hooded merganser
eggs in South Carolina with an average length, width, and mass of53.6?0.3 mm,
43.7?0.1 mm, and 59.0?0.6 g (mean?SE), respectively for 26 eggs. In Missouri, the
mean length, width, and mass ofhooded merganser eggs were 53.7 mm, 43.8 mm, and
57.9 g, respectively for 24 eggs (Dugger et al. 1994). In comparison, length, width, and
mass ofeggs measured in this study were 54.1?0.1 mm, 44.1?O.l mm, and 61.6?0.3 g
(mean?SE), respectively. A possible explanation for the variations in size could be the
sample sizes. The studies from South Carolina and Missouri had very small sample sizes
while the sample size for this study was 238 eggs. Another factor to consider is natural
variation in hooded merganser eggs in one location. A great deal ofvariation in size and
shape was noticed in eggs measured during this study. Egg shape ranged from almost
completely round to slightly elliptical. A few other factors to consider in egg variation
are diet, genetics, and order in which egg was laid.
Eggshell Thickness
Eighty-three hooded merganser eggs were sampled for a mean eggshell thickness
of0.605?0.004 mm (mean?SE). In comparison to previous studies between 1970 and
1981, eggshells from this study appear to be thicker (Table 6). They are almost as thick
as historical eggshell collections from the pre-OC era. There was a 9.4% increase in
thickness between this study and Zicus' study in 1981. This increased thickness may be
an indication ofthe health ofthe laying hooded merganser hens at MCWMA.
50
Table 6. Comparison ofeggshell thickness ofhooded mergansers at MCWMA with
previous studies and historical collections. A decrease in eggshell thickness is shown
from the pre-OC era, through OC use, and after most OCs were banned in the late 1970's.
In 1998, hooded mergansers using nest boxes at MCWMA appear to have eggshells close
to pre-OC era thickness.
Sample Size
OCTime Date Thickness (#clutches/ Location Source
Period (mm) #eggs)
White and
Pre-OC 1880-1927 0.628?0.025 6/55 lA, MI, Comartie,
MN,ND, 1977
WI
Faber and
During use Pre-1947 0.614?0.009 ?/44 WI Hickey,
1973
Faber and
During use 1970 0.599?0.017 ?/11 WI Hickey,
1973
White and
During use 1973-1975 0.576?0.005 28/174 lA, MI, Comartie,
MN,ND, 1977
WI
PostOC 1981 0.568?0.007 21/70 MN Zicus et al.
1988
Post OC 1998 0.605?0.004 14/83 OH This Study
51
The increase could be an indication ofan absence ofor low DC concentrations. It
appeared that even though the use ofmost DC's were banned in the 1970's, they still
persisted in the environment with thin eggshells recorded in 1981 (Zicus 1981). It is
possible that with thicker eggshells in 1998, hooded mergansers may have rebounded
from DC contamination. However, without chemical analysis, this cannot be proven.
It is easy to see a trend in decreased eggshell thickness in relation to use ofDCs
over time. DrganocWorines came to use over seventy years ago (approximately 1930).
Historical collections show the thickest eggshells (White and Cromartie 1977), prior to
DC use. From approximately 1930 to 1975, organochlorines continued to be introduced
into the environment (Bunce 1994, US PHS 1992a, US EPA 1986a, US EPA 1986b). In
the mid 1970's most DC production and use had been banned (Manahan 1994, US PHS
1992a, US PHS 1992b, US PHS 1992c). However, a decrease in eggshell thickness
continued into at least the early 1980s (Zicus et al. 1988). Eggshell thickness from
hooded mergansers nesting at MCWMA appears to approach the pre-DC use range.
Reproductive Success and Parasitism ofHooded Mergansers
Hooded mergansers used 16 ofthe 49 available nest boxes on boxes on both
Eagle Marsh and Wood Duck Marsh. This appeared to be an increase from the 94-95
study, however it was not found to be significant. Nest success appeared to have
decreased between the two studies, however that was also not found to be significant.
Hooded merganser hatching success did have a significant decrease from 94-95 to 1998
(80%-69%). This indicates that hooded merganser nest box use may be increasing and
that increase appears to be impacting their ability to hatch offducklings.
52
Zicus (1990) found that hooded merganser hatching success decreased as clutch
size increased. This could be true for hooded mergansers at MCWMA as well. Between
the 94-95 study and the study in 1998, mean clutch size increased from 14?4.0 to 15?1.5
(mean?SE). An increase in clutch size could be the result ofan increase in intraspecific
nest parasitism. From 94-94 to 1998 the mean number ofparasitic hooded merganser
eggs in hooded merganser nests increased from 4.5?0.5 to 6.6?1.5. In addition, between
94-95 and 1998 there was a significant increase in the number ofhooded merganser nests
parasitized by hooded mergansers from 13% (2/15) to 75% (12/16).
Interspecific nest parasitism ofhooded mergansers by wood ducks does not
appear to be a significant problem for hooded mergansers since it decreased significantly.
Interspecific nest parasitism ofwood ducks by hooded mergansers does not appear to be
impacting wood ducks either because there was no significant change in hatching success
between the two studies.
There also appears to be a slight decrease in reproductive success as eggshell
thickness increases. Although it is not a significant decrease, it may represent an
interesting relationship. Itwould be expected that thicker eggshells would be produced
by a healthier hen and that she would have a high reproductive success. However, the
data from this study seem to indicate the opposite. A possible consideration is that
parasitic hens may lay eggs with thicker eggshells. In this study, some parasitic eggs
may have been inadvertently collected from active hooded merganser nests, resulting in
thicker eggshells per clutch. When they are layed in a box that is near or at the end of
incubation, there is a very good chance that the parasitic eggs will not hatch. This would
lower the percentage ofeggs hatching. Since there was a relatively high incidence of
53
intraspecific nest parasitism ofhooded mergansers, a lower hatching success would be
expected from eggs laid late in the laying period or after incubation had begun.
Nest box density could also be a contributing factor to the increase in intraspecific
nest parasitism ofhooded mergansers nesting at MCWMA. Nest box density on Eagle
Marsh and Wood Duck Marsh was 10 nest boxes/ha (Willis 1996). Typical densities of
natural nest cavities for wood ducks is approximately 3 cavities/ha (Gilmer et al. 1978,
Prince 1968, Strange et al. 1971). Hooded merganser natural nest cavity density is
thought to be similar to that ofthe wood duck. Intraspecific nest parasitism ofwood
ducks was found to be significantly greater in nest boxes at 10 cavities/ha when
compared to 2 cavities/ha (Willis 1996). Semel et al. (1988) found similar results when
comparing visible clumped (VC), visible isolated (VI), and well hidden (WH) nest boxes.
Wood duck clutch sizes in VC nests (16.3 eggs) and VI nests (15.7 eggs) were
significantly larger than clutches in WH nests (12.4 eggs). The larger clutch sizes
appeared to be the result ofa high incidence ofintraspecific nest parasitism. This was
inversely correlated with a decrease in hatch success from well hidden nests (82%) to
visible nests (74%) (Semel et al. 1988). High density and visibility ofnest boxes at
MCWMA may have helped to increase the population and nest box use ofhooded
mergansers however, they may be adversely impacting their overall reproductive success.
Reproductive Success and Parasitism ofWood Ducks
From the 94-95 study to this study, there appeared to be a slight increase in nest
box use and slight decreases in nest success for wood ducks, however not significant.
There was also no change in hatching success between the two studies for wood ducks.
54
Parasitism does not appear to be a contributing factor in the decrease in nest
success for wood ducks. Both intraspecific and interspecific nest parasitism decreased
significantly from 94-95 to 1998.
Predation and abandonment were probably the biggest reason for the decrease in
wood duck nest success. Nest predation accounted for 27% ofwood ducks nest
attempts, most ofwhich appeared to be by raccoons and a few woodpeckers. Crushed
eggs and remnants offur around the nest box entrance was an indication that raccoons
had predated a nest. Holes poked in eggs were usually a sign ofwoodpecker predation.
Nest abandonment accounted for 22% ofall nest attempts. Combined together, nest
predation and abandonment accounted for almost halfofall wood duck nest attempts at
MCWMA in 1998.
Lab/GC Analysis
Unfortunately, due to unknown circumstances, nothing was found in water,
sediment, or egg samples taken at MCWMA. Itis very possible that the Florisil clean-up
column was set up incorrectly and over cleaned the samples, removing any OC residues
that may have been in the samples and all spikes that were added. The method should
have been tested first by running spiked control chicken egg samples on the GC prior to
running actual samples through the clean-up column. There is also a possibility that OC
concentration were actually below a detectable level in the samples and the spikes used
were either old and ineffective or I calculated the concentration ofthe spike wrong.
However, it can be assumed that with the mean eggshell thickness increasing
9.4% from the last study in 1981, OC levels would have been low or absent. For all 83
55
collected eggs, the mean eggshell thickness was 0.605?0.004 mm (mean?SE). That is
near pre-OC era eggshell thickness.
Results ofNull Hypotheses Tests
Eggshell thickness ofhooded merganser eggs at MCWMA do differ from the
eggshell thickness ofhistorical collections. The results ofthis study found the mean
eggshell thickness ofhooded merganser eggs only slightly thinner than historical
collections from the pre-OC era.
Eggshell thickness ofhooded merganser eggs at MCWMA do differ from the
eggshell thickness ofprevious studies. The results ofthis study found mean eggshell
thickness to be thicker than means found in previous studies (from 1970-1981).
The reproductive success ofhooded mergansers from this study does differ from
the reproductive success in 1994 and 1995. There is a significant decrease in hatching
success offrom 94-95 to 1998.
Hooded merganser eggshell thickness does correlate with reproductive success,
although not significantly. As eggshell thickness increased, reproductive success tended
to decrease.
I was unable to determine concentrations ofOCs in hooded merganser eggs to
compare to concentrations ofprevious studies. However, it can be assumed that they
would be low based on the increase in eggshell thickness.
56
Conclusions
Based on the thicker eggshells found in hooded mergansers nesting at MCWMA,
it would be assumed that hens laying there were healthier. Generally, thicker eggshells
would indicate the absence ofor low levels ofOCs, healthy hens, and a healthy
ecosystem. However, the results ofthis study indicate a population ofnesting hens that
may be stressed inspite oftheir thicker eggshells. Other factors seem to be impacting
these birds.
Although this study indicated an increase in nest box use by hooded mergansers,
their hatching success decreased significantly. This may be due to the significant
increase in intraspecific nest parasitism. However, parasitism by parasitic wood ducks
does not appear to be impacting hooded merganser nesting.
Future Work
Although relatively thick eggshells were found during this study and it would be
assumed that organochlorine levels were low, organochlorine levels need to be
confirmed. A new method should be used for extraction and clean-up ofsamples.
With the high occurrence ofnest parasitism, more intensive nest box checks
should be conducted. Rather than checking boxes every two to five days, boxes should
be checked every day. This would allow for determining the number ofhens parasitizing
a box as well as a chronology ofparasitic eggs.
In order to establish the trends ofincreased nest box use, increased parasitism,
and decreased hatching success, nest boxes should continue to be intensively studied at
least every 2 years. This would confirm any trends that were found in this study.
57
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APPENDIX A
FIELD DATA
62
Table 7. Field measurements for eggs measured at Eagle (E) and Wood Duck (WD)
Marsh. Sample #'s indicate eggs that were collected for lab analysis.
63
Sample # Pond Box# Egg # length (mm) width (mm) weight (grams)
E 311 1 58.86 46.23 82.0
1 E 311 2 57.09 47.84 82.0
E 311 3 56.78 47.02 84.0
E 311 4 54.63 46.64 69.5
E 311 5 56.31 46.02 71.0
E 311 6 53.19 43.67 59.0
E 311 7 55.97 46.72 69.5
4 E 311 8 55.94 47.82 71.0
E 311 9 56.89 42.74 60.0
E 311 10 55.02 46.00 67.0
E 311 11 55.27 43.31 61.5
E 311 12 52.69 42.80 57.0
79 E 312 1 52.64 41.93 53.0
47 E 312 2 51.77 44.35 58.0
68 E 312 3 51.06 43.46 57.5
51 E 312 4 51.69 43.71 59.0
40 E 464 1 54.42 44.32 61.5
17 E 464 2 54.30 44.44 61.5
39 E 464 3 52.91 43.27 59.0
44 E 464 4 53.45 44.24 63.0
52 E 464 5 52.95 44.30 61.5
E 465 1 53.34 43.71 59.5
E 465 2 54.50 43.42 59.0
E 465 3 54.57 43.42 60.0
E 465 4 52.28 43.65 59.0
E 465 5 52.14 44.12 58.5
E 465 6 53.14 44.12 60.5
E 465 7 53.77 42.95 57.0
21 E 465 8 55.90 46.57 71.0
E 465 9 53.76 44.83 62.5
53 E 599 1 54.03 42.71 58.0
54 E 599 2 52.56 43.19 56.5
55 E 599 3 53.04 43.11 57.5
56 E 599 4 52.80 44.64 61.0
57 E 599 5 53.73 42.11 56.0
58 E 599 6 53.72 43.56 60.0
8 E 599 7 54.14 44.54 63.5
65 E 599 8 53.93 44.55 60.5
64
66 E 599 9 54.72 44.91 65.0
7 E 599 10 59.32 42.01 71.0
64 E 599 11 53.63 44.66 62.5
67 E 599 12 55.94 43.70 62.5
E 880 1 51.69 43.24 56.0
E 880 2 55.80 44.20 65.0
E 881 1 52.81 43.69 46.5
82 E 881 2 51.74 43.68 56.0
72 WD 388 1 56.30 44.97 62.0
43 WD 388 2 54.91 43.72 61.5
83 WD 388 3 54.18 43.70 60.5
73 WD 388 4 55.93 43.69 62.0
23 WD 388 5 56.55 43.36 62.5
74 WD 388 6 55.10 44.68 64.5
75 WD 388 7 54.33 44.74 64.0
76 WD 388 8 53.56 44.73 63.5
16 WD 388 9 56.45 46.90 72.5
77 WD 388 10 54.87 46.79 71.0
37 WD 388 11 53.96 44.90 64.0
84 WD 388 12 54.01 44.90 65.0
WD 389 1 55.34 43.25 60.0
WD 389 2 54.84 44.94 61.0
WD 389 3 55.39 44.95 60.0
WD 389 4 54.27 43.06 58.0
WD 389 5 56.04 44.15 63.0
WD 389 6 53.11 44.18 61.0
WD 389 7 56.06 43.66 61.0
WD 389 8 53.31 43.13 58.0
WD 389 9 54.33 44.81 60.0
WD 389 10 54.42 44.59 61.0
WD 389 11 56.83 44.60 64.0
WD 389 12 55.98 44.65 62.0
WD 389 13 53.07 44.02 60.5
3 WD 389 14 53.35 45.91 62.0
WD 389 15 54.26 44.26 62.0
WD 389 16 53.41 43.44 59.0
WD 389 17 52.31 43.67 58.0
WD 389 18 59.78 43.37 62.0
WD 389 19 55.52 44.74 64.0
2 WD 389 20 59.68 47.93 77.0
WD 390 1 53.20 42.89 54.0
WD 390 2 54.12 41.73 55.0
65
5 WD 390 3 56.19 44.72 65.0
WD 390 4 53.73 42.73 56.0
WD 390 5 53.17 42.11 56.0
WD 390 6 54.91 44.31 62.0
6 WD 390 7 52.16 45.36 64.5
WD 390 8 53.36 43.07 57.0
WD 390 9 50.54 43.93 54.5
WD 390 10 54.30 44.30 62.5
WD 390 11 53.25 44.96 60.0
WD 390 12 56.14 44.15 62.5
WD 390 13 54.01 45.14 65.0
WD 394 1 53.83 44.59 63.0
14 WD 396 1 53.62 44.88 64.0
13 WD 396 2 53.33 44.18 62.0
15 WD 396 3 53.52 44.32 61.5
WD 396 4 53.29 44.41 62.0
WD 398 1 53.08 41.15 51.0
WD 398 2 53.52 44.93 64.5
WD 398 3 53.58 44.09 62.5
45 WD 398 4 54.10 44.66 60.0
WD 398 5 55.54 44.20 63.5
WD 398 6 53.77 44.31 63.0
WD 398 7 53.54 43.40 60.0
46 WD 398 8 52.72 45.50 65.0
WD 398 9 53.90 43.73 60.0
WD 398 10 53.50 44.91 63.5
WD 398 11 54.14 45.02 65.0
WD 399 1 54.93 45.22 65.0
WD 399 2 55.90 45.03 65.5
69 WD 399 3 53.66 43.66 61.5
WD 399 4 54.79 45.16 66.0
WD 399 5 53.62 43.63 61.5
WD 399 6 53.31 45.49 66.0
WD 399 7 54.80 43.51 60.5
WD 399 8 54.25 45.41 65.0
WD 399 9 52.88 45.12 61.0
80 WD 399 10 54.49 43.50 61.0
WD 399 11 53.36 45.88 65.0
59 WD 400 1 54.69 43.95 61.0
60 WD 400 2 54.47 43.96 61.5
61 WD 400 3 53.61 43.44 59.5
62 WD 400 4 53.03 45.38 64.5
66
63 WD 400 5 54.25 43.38 60.0
70 WD 401 1 53.86 43.24 58.0
71 WD 401 2 53.59 42.56 55.5
27 WD 406 1 53.40 43.02 59.5
38 WD 408 1 55.60 43.79 63.0
35 WD 408 2 55.03 44.37 64.0
50 WD 408 3 56.01 43.74 63.0
WD 412 1 54.00 43.93 58.5
WD 481 1 55.58 42.77 59.5
41 WD 481 2 53.86 42.98 59.5
WD 481 3 54.54 42.28 57.5
WD 481 4 54.80 43.18 61.0
WD 481 5 53.72 42.60 58.0
WD 481 6 55.12 43.72 61.5
42 WD 481 7 53.93 44.13 60.0
WD 481 8 54.63 43.27 60.0
WD 481 9 53.95 43.92 60.5
WD 481 10 54.40 43.78 60.0
WD 481 11 54.03 44.58 62.5
WD 481 12 55.25 43.48 59.5
WD 481 13 55.18 43.46 61.0
WD 481 14 55.52 43.88 61.5
WD 481 15 53.71 45.77 65.5
WD 481 16 52.14 41.85 54.0
WD 481 17 54.00 43.82 61.0
WD 481 18 53.11 45.77 66.0
WD 482 1 56.42 41.77 55.5
WD 482 2 52.68 43.35 58.0
WD 482 3 55.09 41.93 53.0
WD 482 4 52.30 43.47 58.5
WD 482 5 56.00 42.90 57.0
WD 482 6 53.26 43.56 59.0
WD 482 7 54.73 43.69 60.0
WD 482 8 54.34 42.38 57.0
WD 482 9 53.36 42.02 54.5
WD 482 10 53.79 43.10 57.5
WD 482 11 53.03 43.74 60.5
WD 482 12 52.19 41.89 53.0
WD 482 13 54.41 43.82 60.0
WD 482 14 54.87 42.45 58.0
18 WD 803 1 54.51 45.30 66.0
9 WD 803 2 54.31 43.23 62.5
67
11 WD 803 3 55.48 44.50 66.5
WD 804 1 56.98 45.04 64.5
WD 804 2 56.76 44.65 65.0
WD 804 3 53.78 45.05 63.0
WD 804 4 51.55 42.58 55.5
WD 804 5 53.05 43.30 57.5
WD 804 6 54.90 44.68 64.5
12 WD 804 7 51.29 44.43 60.5
WD 804 8 51.65 43.69 58.5
WD 804 9 52.39 45.21 62.5
WD 805 1 52.87 44.91 62.0
WD 805 2 53.74 43.81 60.5
WD 805 3 54.95 44.45 65.0
WD 805 4 53.10 46.30 66.0
WD 805 5 53.82 44.07 61.5
WD 805 6 54.04 44.75 63.5
WD 805 7 52.43 44.32 59.0
WD 805 8 53.81 43.09 58.5
WD 805 9 53.26 45.25 62.5
19 WD 805 10 52.64 43.22 57.0
WD 805 11 52.67 42.99 57.5
WD 805 12 53.46 45.15 63.0
WD 805 13 53.09 43.39 59.0
WD 805 14 54.27 45.60 65.0
WD 805 15 55.73 44.83 65.0
20 WD 805 16 53.94 44.89 63.5
WD 805 17 54.78 43.71 60.5
WD 805 18 55.06 44.93 65.0
WD 805 19 53.85 44.31 62.0
WD 805 20 52.84 43.31 58.0
WD 805 21 54.13 44.07 62.0
WD 805 22 52.43 44.29 60.5
WD 841 1 52.39 45.57 64.0
WD 841 2 53.02 45.12 63.5
WD 841 3 52.93 45.24 63.0
WD 841 4 53.35 45.57 66.0
WD 841 5 53.72 45.12 65.0
WD 841 6 53.87 44.84 64.5
10 WD 842 1 52.54 43.78 60.5
24 WD 843 1 51.97 42.98 55.0
WD 844 1 52.54 45.01 64.0
WD 844 2 56.06 43.64 63.0
68
WD 844 3 54.28 45.52 66.0
WD 844 4 50.65 42.63 56.0
30 WD 844 5 53.78 44.49 63.5
WD 844 6 54.35 44.26 63.0
WD 844 7 51.70 43.81 59.0
WD 844 8 54.66 44.42 64.0
WD 844 9 55.72 44.48 63.5
78 WD 844 10 52.91 43.78 60.0
WD 844 11 51.36 44.33 59.0
WD 844 12 52.06 42.58 56.0
WD 844 13 54.71 43.05 59.0
WD 844 14 55.00 43.00 59.0
WD 844 15 55.14 43.62 61.0
33 WD 845 1 54.42 45.22 67.0
25 WD 845 2 53.96 44.05 63.0
36 WD 845 3 52.42 45.58 65.5
29 WD 845 4 55.73 43.45 63.0
22 WD 845 5 53.40 44.69 63.5
32 WD 845 6 53.72 44.92 64.0
28 WD 845 7 55.12 43.05 61.0
31 WD 845 8 54.29 43.32 61.0
34 WD 845 9 55.Ql 45.04 64.5
26 WD 845 10 52.27 43.14 58.0
WD 846 1 52.41 43.90 61.0
WD 846 2 53.44 42.98 58.0
WD 846 3 53.91 43.19 61.0
WD 846 4 53.33 43.48 60.0
49 WD 846 5 52.84 45.70 64.5
WD 846 6 54.07 43.46 60.0
WD 846 7 53.20 43.04 58.5
WD 846 8 54.55 45.15 60.0
48 WD 846 9 55.77 44.74 65.5
*Mean +/- SE 54.1+/- 0.1 44.1+/- 0.1 61.6+/- 0.3
Table 8. Field and lab measurements for 83 eggs collected from Eagle (E) and Wood
Duck (WD) Marsh.
69
Sample # Box# Egg # length(mm) width(mm) weight(g) thickness(mm) Shell wt (g) **Ratcliffe
1 311 2 57.09 47.84 82.0 0.584 10.2493 3.753
2 389 20 59.68 47.93 77.0 0.593 10.7973 3.775
3 389 14 53.35 45.91 62.0 0.643 10.4579 4.270
4 311 8 55.94 47.82 71.0 0.559 10.5728 3.952
5 390 3 56.19 44.72 65.0 0.542 9.3642 3.727
6 390 7 52.16 45.36 64.5 0.635 10.5277 4.450
7 599 10 59.32 42.01 71.0 0.618 11.4362 4.589
8 599 7 54.14 44.54 63.5 0.567 9.4423 3.916
9 803 2 54.31 43.23 62.5 0.584 10.1725 4.333
10 842 1 52.54 43.78 60.5 0.635 10.0978 4.390
11 803 3 55.48 44.50 66.5 0.593 10.4320 4.225
12 804 7 51.29 44.43 60.5 0.610 9.8149 4.307
13 396 2 53.33 44.18 62.0 0.635 10.2613 4.355
14 396 1 53.62 44.88 64.0 0.627 10.3225 4.289
15 396 3 53.52 44.32 61.5 0.635 10.0754 4.248
16 388 9 56.45 46.90 72.5 0.660 11.3549 4.289
17 464 2 54.30 44.44 61.5 0.635 9.9717 4.132
18 803 1 54.51 45.30 66.0 0.635 10.2914 4.168
19 805 10 52.64 43.22 57.0 0.584 9.3540 4.111
20 805 16 53.94 44.89 63.5 0.584 10.1075 4.174
21 465 8 55.90 46.57 71.0 0.669 11.3693 4.367
22 845 5 53.40 44.69 63.5 0.610 10.1884 4.269
23 388 5 56.55 43.36 62.5 0.601 9.3295 3.805
24 843 1 51.97 42.98 55.0 0.483 6.8855 3.083
25 845 2 53.96 44.05 63.0 0.584 9.6724 4.069
26 845 10 52.27 43.14 58.0 0.610 8.9838 3.984
27 406 1 53.40 43.02 59.5 0.635 9.9165 4.317
28 845 7 55.12 43.05 61.0 0.610 9.6107 4.050
29 845 4 55.73 43.45 63.0 0.627 9.4887 3.919
30 844 5 53.78 44.49 63.5 0.584 9.6288 4.024
31 845 8 54.29 43.32 61.0 0.635 9.9718 4.240
32 845 6 53.72 44.92 64.0 0.618 9.6362 3.993
33 845 1 54.42 45.22 67.0 0.635 10.7413 4.365
34 845 9 55.01 45.04 64.5 0.559 9.5907 3.871
35 408 2 55.03 44.37 64.0 0.635 10.5408 4.317
36 845 3 52.42 45.58 65.5 0.601 9.7773 4.092
37 388 11 53.96 44.90 64.0 0.635 10.1381 4.184
38 408 1 55.60 43.79 63.0 0.610 9.9602 4.091
39 464 3 52.91 43.27 59.0 0.610 9.6363 4.209
40 464 1 54.42 44.32 61.5 0.610 9.7468 4.041
41 481 2 53.86 42.98 59.5 0.593 9.1728 3.962
42 481 7 53.93 44.13 60.0 0.542 8.7559 3.679
43 388 2 54.91 43.72 61.5 0.635 9.6055 4.001
44 464 4 53.45 44.24 63.0 0.669 10.3594 4.381
45 398 4 54.10 44.66 60.0 0.610 10.0962 4.179
46 398 8 52.72 45.50 65.0 0.660 10.6644 4.446
47 312 2 51.77 44.35 58.0 0.593 9.0943 3.961
70
48 846 9 55.77 44.74 65.5 0.610 10.1692 4.076
49 846 5 52.84 45.70 64.5 0.610 10.1253 4.193
50 408 3 56.01 43.74 63.0 0.635 9.7980 3.999
51 312 4 51.69 43.71 59.0 0.618 9.3111 4.121
52 464 5 52.95 44.30 61.5 0.601 9.7924 4.175
53 599 1 54.03 42.71 58.0 0.525 8.1787 3.544
54 599 2 52.56 43.19 56.5 0.584 8.6404 3.806
55 599 3 53.04 43.11 57.5 0.601 9.0469 3.957
56 599 4 52.80 44.64 61.0 0.559 8.7822 3.726
57 599 5 53.73 42.11 56.0 0.593 8.7360 3.861
58 599 6 53.72 43.56 60.0 0.533 9.1135 3.895
59 400 1 54.69 43.95 61.0 0.610 9.2711 3.857
60 400 2 54.47 43.96 61.5 0.525 8.6232 3.601
61 400 3 53.61 43.44 59.5 0.567 8.9706 3.852
62 400 4 53.03 45.38 64.5 0.584 9.7698 4.060
63 400 5 54.25 43.38 60.0 0.610 9.6389 4.096
64 599 11 53.63 44.66 62.5 0.618 10.0173 4.182
65 599 8 53.93 44.55 60.5 0.584 9.3169 3.878
66 599 9 54.72 44.91 65.0 0.618 10.2950 4.189
67 599 12 55.94 43.70 62.5 0.618 9.7718 3.997
68 312 3 51.06 43.46 57.5 0.610 9.1973 4.145
69 399 3 53.66 43.66 61.5 0.635 10.2594 4.379
70 401 1 53.86 43.24 58.0 0.618 9.5045 4.081
71 401 2 53.59 42.56 55.5 0.559 8.3866 3.677
72 388 1 56.30 44.97 62.0 0.627 9.8526 3.892
73 388 4 55.93 43.69 62.0 0.610 9.4417 3.864
74 388 6 55.10 44.68 64.5 0.627 10.3298 4.196
75 388 7 54.33 44.74 64.0 0.660 10.2106 4.201
76 388 8 53.56 44.73 63.5 0.660 10.4632 4.367
77 388 10 54.87 46.79 71.0 0.660 11.1424 4.340
78 844 10 52.91 43.78 60.0 0.610 9.6014 4.145
79 312 1 52.64 41.93 53.0 0.525 7.7186 3.497
80 399 10 54.49 43.50 61.0 0.618 9.7295 4.105
82 881 2 51.74 43.68 56.0 0.559 8.8321 3.908
83 388 3 54.18 43.70 60.5 0.610 9.8379 4.155
84 388 12 54.01 44.90 65.0 0.635 10.5079 4.333
*Mean +/- SE 54.1 +/- 0.2 44.3 +/- 0.1 62.5 +/- 0.5 0.605+/-0.004 9.76+/-0.08 4.069+/-0.028
**Ratcliffe Index from Ratcliffe, 1967.
Table 9. Nest box summaries for hooded merganser and wood ducks nesting at
MCWMA. Duck (WD) Marsh. D=Drop nest, T=tree swallow nest, G=grackle
nest, A=Abandoned nest, P=Predated nest, S=Successful nest.
1998 Mosquito Creek Nest Box Data Summary 1
71
Box # Nest # Spp Fate !it HM laid #WD laid #HM prior #WDprior!#HM hatcIJ #WD hatch
400WD 1 HM D 5 0 0 0 0 0
387WD 2 TS T 0 0 0 0 0 0
404 WD 1 TS T 0 0 0 0 0 0
414 WD 1 GR G 0 0 0 0 0 0
599 E 1 HM A 12 0 0 0 0 0
388 WD 1 HM A 12 1 0 0 0 0
312 E 1 WD A 4 13 0 0 0 0
463 E 1 WD A 0 14 0 0 0 0
881 E 1 WD A 2 12 0 0 0 0
387WD 1 WD A 0 24 0 0 0 0
388 WD 2 WD A 0 11 0 0 0 0
408WD 1 WD A 3 10 0 0 0 0
412 WD 1 WD A 1 22 0 0 0 0
843 WD 1 WD A 1 18 0 0 0 0
399WD 1 HM P 11 0 0 0 0 0
464 E 1 WD P 5 23 0 0 0 0
599 E 2 WD P 0 6 0 0 0 0
880 E 1 WD P 2 11 0 0 0 0
386WD 1 WD P 0 17 0 0 0 0
389WD 2 WD P 0 6 0 0 0 0
394 WD 1 WD P 1 21 0 0 0 0
402 WD 1 WD P 0 4 0 0 0 0
405 WD 1 WD P 0 12 0 0 0 0
407WD 1 WD P 0 7 0 0 0 0
408WD 2 WD P 0 8 0 0 0 0
2
Box # Nest # Spp Fate 1# HM laid #WD laid #HMprior #WD prior #HMhatcb #WD hatcb
311 E 1 HM S 15 1 13 0 13 0
465 E 1 HM S 9 2 8 2 5 2
389WD 1 HM S 20 0 18 0 12 0
390WD 1 HM S 15 0 13 0 12 0
398 WD 1 HM S 20 0 18 0 17 0
481 WD 1 HM S 18 0 16 0 16 0
482WD 1 HM S 14 0 12 0 12 0
804WD 1 HM S 12 0 10 0 9 0
805 WD 1 HM S 22 1 20 1 6 1
841 WD 1 HM S 6 6 6 6 6 6
844 WD 1 HM S 15 0 13 0 8 0
462E 1 WD S 1 24 1 22 1 12
390WD 2 WD S 0 17 0 17 0 11
391 WD 1 WD S 2 15 2 15 2 15
392WD 1 WD S 0 12 0 12 0 12
393 WD 1 WD S 0 15 0 14 0 14
395 WD 1 WD S 0 13 0 13 0 6
396WD 1 WD S 4 13 1 13 1 12
397WD 1 WD S 0 9 0 9 0 6
401WD 1 WD S 0 13 0 13 0 10
403 WD 1 WD S 0 21 0 21 0 18
406WD 1 WD S 2 9 1 9 0 4
409WD 1 WD S 0 23 0 23 0 16
411 WD 1 WD S 0 32 0 32 0 30
803 WD 1 WD S 3 21 0 21 0 16
842WD 1 WD S 1 21 1 21 1 17
845 WD 1 WD S 10 19 0 19 0 17
846WD 1 WD S 10 11 8 7 8 7
847WD 1 WD S 0 20 0 20 0 17
848 WD 1 WD S 0 23 0 23 0 21
147 324 116 261
Totals: 55 258 581
72
APPENDIXB
EQUATIONS
73
INITIATOR: PACF
NUMBER: 21.060
STANDARD OPERATING PROCEDURES
PWRC - ECR BRANCH
PACF CHEMISTRY SECTION
DATE OF IMPLEMENTATION: October 6, 1988
74
TITLE: Percent Lipid Determinations.
SCOPE: Method is appropriate to determine lipid weights without
taking entire sample to dryness.
DATA QUALITY EXPECTATIONS: Coefficient of variation is <5.0%.
Summary: A portion of the extracted lipid solution is placed on a
pre-weighed aluminum pan. The solvent is evaporated from pan and
the pan is reweighed. The percent lipid is calculated
accordingly as described in detail below.
PROCEDURE:
Pre weigh aluminum pan on analytical balance. Pipet into pan
either 1 mL if sample extract is at 10 mL prior to florisil
cleanup or 2 mL if sample is at 20 mL prior to florisil cleanup.
Evaporate solvent and reweigh pan. Check volume of sample tube
and mark with a marker. Remember this may affect the dilution
factors for the calculation of ppm pesticides.
CALCULATIONS:
PE Pan Empty
PF Pan Full after solvent has been evaporated
Al Sample aliquot
% Lipid = ((PF-PE) * 10jAl) * 100
PROBLEMS: Samples low in lipid such as muscle tissue may be
difficult to determine lipid weight.
DOCUMENTATION: All data is included in weightbook.
RESULTS: Percent lipid is reported.