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Title: Mercury Concentrations in Tissue of Florida Bald Eagles
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Title: Mercury Concentrations in Tissue of Florida Bald Eagles
Physical Description: Book
Language: English
Creator: Wood, Petra Bohall
White, John
Steffer, Anthony
Wood, John M.
Percival, H. Franklin
Affiliation: West Virginia University -- Morgantown -- West Virginia Cooperative Fish and Wildlife Research Unit
West Virginia University -- Morgantown -- Division of Forestry
University of Florida -- Gainesville, Fla. -- Florida Cooperative Fish and Wildlife Research Unit
Publication Date: 1993
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Bibliographic ID: UF00001462
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: ltqf - AAA0754
ltuf - AKB4195
alephbibnum - 001938061
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    Acknowledgement
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West Virginia Cooperative Fish and Wildlife Research Unit
West Virginia University
P.O. Box 6125, 333 Per ival H.1l
Morgantown, WV 26505-6125
(304) 293-3794 Ext 433 or 430
FAX 304-293-2441


3 January 1994

Dr. Charles Facemire
USFWS, region 4
7 Spring Street, SW
Atlanta GA 30303

Dear Chy~k:

Enclosed ip the final report for the study of mercury in Florida bald eagles. I think
that we got a good handle on background levels of mercury. If you have any
comments or criticisms that need to be addressed in the report, please let me
know and I will modify it.

Thank you for your support of this study.

Sincerely,



Petra Bohall Wood
Assistant Unit Leader Wildlife
and Assistant Professor
Internet: pbwood@wvnvm.wvnet.edu


cc. H. Franklin Percival
Doug Morrison










MERCURY CONCENTRATIONS IN TISSUES OF FLORIDA BALD EAGLES


FINAL PROJECT REPORT

December 1993



Submitted by:

Petra Bohall Wood
West Virginia Coop. Fish and Wildlife Research Unit
West Virginia University
P.O. Box 6125
Morgantown WV 26506-6125

John White
Florida Game and Fresh Water Fish Commission
P.O. Box 1903
Eustis FL 32727

Anthony Steffer
Biological Research Associates
3910 US Highway 301 North
Suite 180
Tampa FL 33619

John M. Wood
Division of Forestry
West Virginia University
P.O. Box 6125
Morgantown WV 26506-6125

H. Franklin Percival
Florida Coop. Fish and Wildlife Reseach Unit
University of Florida
117 Newins-Ziegler Hall
Gainesville FL 32611



Submitted to:

Charles Facemire
U. S. Fish and Wildlife Service
75 Spring Street, SW
Atlanta GA 30303


MVERsTY OF FLOR1 u LIBRARY








ACKNOWLEDGEMENTS

Many people contributed to the success of this study; to all of them we are

grateful. We thank the many landowners in Florida who granted us access to eagle nests

on their property. Without their cooperation, this study would not have been possible.

We thank Carlton Hardy for climbing some of the eagle nest trees. The staff of the Florida

Audubon Society Birds of Prey Center supplied tissue samples from bald eagles under their

care. The staff of the National Wildlife Health Research Center, particularly Greg Kidd,

supplied tissues from carcasses of eagles collected in Florida. We also thank the curators

of museums who provided us samples from Florida bald eagle specimens in their

collections. This included the American Museum of Natural History, the Florida Museum

of Natural History, University of Miami, University of Michigan Museum of Zoology,

University of Wisconsin Zoological Museum, and Yale University Peabody Museum.

Marilyn Spalding, University of Florida, provided unpublished data on mercury

concentrations in wading birds. Elwin Evans, Michigan Department of Natural Resources,

provided unpublished data on mercury concentrations in bald eagles and red-tailed hawks.

The U.S. Fish and Wildlife Service allowed use of unpublished mercury data from bald

eagle feathers collected in 1991 at nest PO40 and from fish collected at National Wildlife

Refuges in Florida. Stanley Wiemeyer, U.S. Fish and Wildlife Service, freely gave his

advice on various aspects of this study.

Primary funding for this study was provided by the U.S. Fish and Wildlife Service,

Region 5 Contaminants Office. Additional funding was provided by the University of

Florida. We thank Stephen Sundlof, College of Veterinary Medicine, University of Florida

for chemical analyses of 1992 blood and feather samples. We also thank the staff of

Hazleton Environmental Services, Inc. for analyses of the 1993 samples and for providing

information on analysis methods.









INTRODUCTION

High mercury (Hg) concentrations have been documented in several aquatic

systems throughout Florida (Hord et al. 1990, Royals and Lange 1990, Ware et al. 1990).

As a top predator of aquatic systems, bald eagles (Haliaeetus leucoceohalus) can bio-

accumulate mercury resulting in elevated concentrations in tissues (Wiemeyer et al. 1984,

1989). The efficiency of mercury transfer between trophic levels is amplified at high

trophic levels (Eisler 1987). Elevated mercury concentrations in adult eagles can have

negative effects on productivity (Wiemeyer et al. 1984).

Mercury concentrations in species that are often found as eagle prey in Florida

highlight the potential problem of bio-accumulation. Although various species of fish,

including many high-level predators such as catfish (Ictalurus spp.), gar (Lepisosteus spp.),

pickerel (Esox spp.), and bowfin (Amia calva) are a large part of the diet of bald eagles in

Florida, they also feed extensively on all species of wading birds, coots (Fulica americana),

other waterfowl, and a variety of mammals, herptiles, and other birds (P.B. Wood and A.

Steffer, unpubl. data).

High concentrations of mercury have been found in liver tissue of wading birds,

particularly those that feed on large fish (Table 1) (M. Spalding, pers. commun.). Mottled

duck (Anas fulviqula) mercury concentrations are relatively low. This species is

representative of coots, common moorhens (Gallinula chloropus) and purple gallinules

(Porohvrula martinica) which also are herbivorous. Largemouth bass (Micropterus

salmoides) have fairly high concentrations. Ware et al. (1990) found that 51 of 80 lakes

and rivers sampled had mean mercury concentrations in bass greater than 0.5 mg/kg, a

level the U.S. Food and Drug Administration (FDA) considers dangerous for human

consumption. Mercury in gar and bowfin also was high, up to 7 ppm.










Prior to this study, no information was available on current or historic mercury

concentrations in bald eagles in Florida. With the increase of waste incinerators

throughout the state and increasing mercury concentrations in many aquatic systems, it

was important to obtain baseline information on bio-accumulation of mercury. Because

eagles are widespread throughout the state and are a top-level predator of aquatic

systems, they are a good indicator species.



OBJECTIVES

We designed this study to determine past and present mercury concentrations in

eagles using 3 sources of data. First, we collected blood and feather samples from

nestling bald eagles and feathers of adult eagles at specific nest sites to examine mercury

concentrations in relation to characteristics of nearby lakes and to assess current

concentrations of mercury in Florida eagles. Second, we obtained tissues (primarily liver)

from eagle carcasses collected throughout the state of Florida as another source of data to

document current concentrations. Third, we obtained feather samples from bald eagle

museum specimens that were collected in Florida during the late 1800's and early 1900's

to determine historic concentrations of mercury in Florida eagles.



STUDY AREA AND METHODS

We obtained samples from nests associated with 20 water bodies (18 natural lakes,

1 phosphate pond, and the Gulf of Mexico) throughout north and central Florida (Figure 1)

during this study. The original plan was to collect samples during March and April from 15

nests in 4 areas (n= 60) from several different river and wetland systems, with at least 4

nests located on the same lake or river system. In mid March 1993, however, a severe

winter storm interrupted nesting (nestlings and/or nests were blown out) at several bald









eagle nests that we had planned to sample. In addition, early nesting by many pairs of

eagles resulted in young that were too old to safely remove from their nest in March and

April. Consequently, we collected samples from every climbable, surviving nest with

nestlings of the right age and where access was granted by the landowner. The March

storm also resulted in injuries to several nestling eagles that were treated at the Florida

Audubon Society, Birds of Prey Center, in Maitland. We obtained samples from these

birds also.

Nestlings were the original focus of the study for several reasons. First, it is easier

to collect samples from large numbers of nestlings and to tie specific nests to the nearby

foraging areas of the adults. Any mercury found in nestlings would have to come from

prey provided by adults. Thus, the source of mercury in nestlings can be assumed to be

the nearby foraging areas of the nesting adults. Conversely, adult and subadult eagles are

very difficult to capture; thus sample size would be very small. Individual subadults

frequently range over a large portion of Florida, making it difficult if not impossible to

pinpoint the source of any residues detected.

Each nestling was removed from its nest by a tree climber (usually A. Steffer)

experienced with handling nestling eagles and lowered to the ground in a duffel bag. All

measuring, banding, and sampling was completed by personnel on the ground. Each

nestling was banded with a USFWS aluminum leg band on the right leg. We measured bill

depth, length of the foot pad, length of the eighth primary and weighed each nestling.

We collected both blood and feather samples from each of the nestlings banded.

Nestling feather samples will be used as a comparison for adult feather mercury

concentrations. Mercury concentrations in blood are less variable than those in feathers

and represent mercury obtained from prey recently ingested (S. Wiemeyer, pers.










commun.). Feather mercury concentrations of nestlings represent mercury concentrated

during the life of the nestling.

We removed the outer 2/3 of 5 lower breast/upper abdominal feathers from older

nestlings (7-9 weeks old). Younger or less developed nestlings have somewhat smaller

breast feathers, so we increased the sample to 7 feathers to obtain approximately the

same amount of feather material for each bird. Body feathers provide the most

representative sample for estimating mercury concentrations and show the least variation

between feathers (Furness et al. 1986). Breast and abdominal feathers emerge on

nestlings at about 4-6 weeks after hatch (Bortolotti 1984).

Blood samples from nestlings were drawn from the brachial vein in the right wing

with a 2-cc, sterilized syringe. We collected 1-2 cc of blood per bird. A fresh syringe and

needle were used for each sample. Blood samples were transferred immediately to

heperinized vacuum containers and placed in a cooler while in the field. They were stored

frozen until they were shipped to the chemical analysis lab.

Because we could not obtain blood samples from nesting adults, we used feathers

to compare mercury concentrations in adults and nestlings. We collected all adult feathers

that we found on the ground in the immediate vicinity of each nest. Each feather type

(primary, secondary, tertiary, and contour) was chemically analyzed as a separate sample.

Eagles are territorial at their nest sites, therefore, we assumed the feathers were from

the breeding pair at a given nest. Breeding adults appear to be non-migratory, thus much

of the mercury present in adult feathers likely was accumulated in Florida near the

breeding territory. Mercury concentrations in adult eagle feathers should be only slightly

less than when the feather was molted since Appelquist et al. (1984) found a less than

10% change in mercury concentration in guillemot (Uria aalae) and black guillemot

(Ceophus rvlle) feathers exposed to various environmental factors for 8 months.


M









One objective of this study was to not only determine baseline mercury

concentrations in nestling and adult eagles, but also to try and identify from which lakes

birds were obtaining mercury. We mapped the distribution of mercury concentrations in

feathers of adults and nestlings by lakes. To map the distribution of feather mercury

concentrations in eagles, we grouped the data into 3 categories: <5 ppm, 5-11 ppm,

> 11 ppm. We selected these cutoffs because Eisler (1987) reported that 5-11 ppm of

mercury in feathers for various bird species was associated with reduced hatch and

sterility. In addition, Heinz (1979) reported that 9-11 ppm mercury in mallard feathers

was associated with behavioral changes and reduced reproduction. However, it is not

known if mercury in feathers at these concentrations will affect eagles in the same way.

We examined pH (Canfield 1981) and trophic state index (Brezonik et al. 1982) of each

lake to determine if they influence mercury bio-accumulation in bald eagles.

We recorded all prey remains found at each nest site. We also searched for fresh

prey in and under each eagle nest visited. We found fresh fish at 3 nests and collected a

small portion of muscle tissue for analysis of mercury contamination. The remainder of

the fish was replaced in the nest. Each prey item found was ranked according to its

position in the food chain (F. Margraf pers. commun., Martin et al. 1951, Collins 1981);

1.0 for herbivores, 2.0 for first-level carnivores, and 3.0 for higher-level carnivores. We

gave carnivores a higher index to reflect the bio-accumulation of mercury in higher levels

of the food chain. We assumed that aquatic prey species would bio-accumulate more than

terrestrial prey species. Therefore, ranks given to terrestrial prey were adjusted by

multiplying by 0.5, while aquatic prey species' ranks were not adjusted. A food-chain

index was calculated for each nest that contained prey remains by averaging the ranks of

all the prey species found in each nest. A nested analysis of variance (ANOVA), which

adjusted for differences among lakes, was used to test the hypothesis that the










concentration of mercury in the blood and feathers of nestlings is positively correlated with

the trophic position of the prey found at each nest. The ANOVA included lake and food-

chain index nested within lake as dependent variables. Although we realize that prey

remains collected at nests are not a complete picture of the diet of each pair of eagles,

these food-chain indices are at least a rough approximation of where on the trophic level

individual eagles are feeding.

We contacted the National Wildlife Health Research Center, the Florida Audubon

Society Birds of Prey Center, and the Southeastern Raptor Rehabilitation Center to obtain

liver, feather, and/or blood samples from eagle carcasses recovered throughout Florida. To

obtain information on historic concentrations of mercury in Florida bald eagles, we

contacted 13 museums throughout the United States for lower breast/upper abdominal

feather samples from Florida eagle specimens. Mercury concentrations in these feather

samples provide a historical perspective on changes in environmental levels over time and

were compared to the mercury concentrations of feathers collected from adults at nest

sites.

All blood, feather, and liver samples obtained in 1993 were analyzed for mercury

concentrations at Hazleton Environmental Laboratory, Inc., a laboratory approved by

Patuxent Analytical Control Facility. Blood and liver samples were shipped to the

analytical laboratory frozen on dry ice. The 1992 samples were chemically analyzed by a

laboratory at the School of Veterinary Medicine, University of Florida. All mercury

concentrations are presented in mg/kg (ppm) wet weight. Data were analysed with the PC

version 6.3 of the Statistical Analysis System (SAS) on a micro-computer. Specific

statistical tests used are presented in the results.










RESULTS AND DISCUSSION

We obtained blood and feather samples from nestling eagles at 33 nests on 18

lakes and adult feather samples from 20 nests on 10 lakes in 1993 (Table 2). The 1993

data included samples from 11 nestlings from 7 nests that were treated at the Florida

Audubon Society, Birds of Prey Center. Two other nestlings died and we obtained blood,

feather, and liver samples for this study. P. Wood and A. Steffer collected 9 samples from

5 nests on 3 lakes in 1992.

Mean mercury concentrations for nestlings were lowest in blood and highest in

feathers (Table 3). Nestlings had lower mercury concentrations in feathers than adults, a

result of bio-accumulation in adults over time. Adult contour feathers had a slightly higher

mean level of mercury than all adult feathers combined (Table 3). However, the

distribution of mercury concentrations in adult feathers was similar for contours and all

feathers combined (Figure 2) (Fischer's exact test: 2 = 2.69, E= 0.74). For all further

analyses we used the concentrations in all feathers for adults because sample size is

larger.

We obtained liver, feather, and/or blood samples from 31 eagle carcasses recovered

throughout Florida (Table 4). Chemical analyses on six of these are not yet completed.

Mercury concentrations in 24 liver samples were not different by age (F= 1.38, P =0.28),

although nestlings had lowest levels (Table 5). The overall mean mercury concentration

was 2.74 mg/kg. The concentrations found in adult and nestling livers in Florida are well

below concentrations of mercury residues (> 20 ppm) found in tissues of other birds that

died of mercury poisoning (Finley et al. 1979). In a review of mercury studies on birds,

Ohlendorf (1993) found that <1-10 ppm of mercury in liver was considered a normal

background level for birds in general by some authors, while >6 ppm was considered










toxic by others. Red-tailed hawks (Buteo jamaicensis) that died of mercury poisoning had

16.7-20.0 ppm of mercury in the liver (E. Evans, pers. commun.).

To determine if mercury concentrations in Florida eagles might be cause for

concern, we compared data from our study with mercury concentrations in captive eagles

(Table 6). The latter can be considered representative of background levels (Ohlendorf

1993). Mean mercury concentrations in blood of captive adult eagles (0.23 ppm) was

similar to that of Florida nestlings (0.20 ppm). However, some Florida nestlings had blood

mercury concentrations over twice as high as captive adults, up to 0.73 ppm. Feather

mercury concentrations in both nestlings and adults were considerably higher than in

captive eagles (Table 6). Apparently some Florida eagles are bio-accumulating mercury to

concentrations higher than background levels.

Nestling bald eagles in Florida had mean blood mercury concentrations similar to

nestlings from Maine and Washington (Table 6). Nestlings from Oregon had the highest

blood mercury concentrations. Feather mercury concentrations were only half that found

in Maine and Great Lakes nestlings. Adult feather mercury concentrations were similar to

those found in Alaska, but much lower than adults sampled on the Great Lakes. Eisler

(1987) reported that 5-11 ppm of mercury in feathers for various bird species was

associated with reduced hatch and sterility. Heinz (1979) reported that 9-11 ppm mercury

in mallard feathers was associated with behavioral changes and reduced reproduction.

Sterility was observed in sparrowhawks Accioiter niu at 40 mg/kg of mercury in feathers

(Solonen and Lodenius 1984). Liver concentrations in adult and subadult Florida eagles

were higher than found in liver in Oregon eagles. Thus, Florida eagles are bio-

accumulating mercury above background levels but not to the extent of Great Lakes eagle

populations. It is not known, however, what effects low levels of mercury have on eagles


r







and at what concentration eagles might become impaired resulting in death from other

sources of mortality.

We obtained nestling blood and feather samples from 22 nests with 2 or 3 young

(Table 2). There was no significant difference (_ difference = -0.02, SE =0.02, t =-1.22,

P=0.24) between blood mercury concentrations in siblings using a paired-difference t-test.

We also compared feather mercury concentrations in siblings and again found no

significant difference (x difference = -0.11, SE=0.39, t=-0.28, E=0.78). We then

calculated mean nestling and adult feather mercury concentrations for each nest and

compared them using Pearson product-moment correlation. When we excluded 1 outlier,

we found a positive correlation (r =0.63, P<0.02) between adult and nestling feather

mercury concentrations (Figure 3). Nests with high adult feather mercury concentrations

had high nestling feather concentrations.

We also examined the relationship between mercury concentrations in nestling

feathers and blood. A Pearson product-moment correlation on both years of data

combined was not significant (n=57, r=0.23, E=0.08) (Figure 4). However, the plotted

data showed a pattern of 2 diverging lines. When we examined only the 1993 data and

omitted 2 outliers, we found a positive correlation (n =46, r =0.81, P=0.0001) between

nestling blood and feather mercury concentrations (Figure 5). In 1992, there was no

relationship between blood and feather mercury concentrations, possibly because the

1992 data were analyzed by a different laboratory with less sensitive equipment; the

lowest concentration of mercury in nestling blood in 1992 was greater than the mean in

1993 (Table 3).

We sampled nestlings at 3 nests in both 1992 and 1993 (Figure 6) and obtained

data from adult feathers at one nest (P040) in 2 years. Statistical analyses were not

performed because of small sample size. In all nestling samples, 1992 blood mercury








10

concentrations were slightly higher; again likely the result of having 2 different labs do the

chemical analyses resulting in higher detection levels for 1992 samples. At 2 nests,

nestling feather mercury concentrations were somewhat higher in 1993. At one nest,

AL17, the 1993 nestling feather mercury level was considerably higher than in 1992.

Mercury concentrations in adult feathers from nest P040 was 5.87 mg/kg in 1991

compared to 8.84 mg/kg in 1993.

We obtained blood, feather, and liver samples from 3 eagles, 2 nestlings and a 2-

year-old bird (Figure 7). Three samples were insufficient to statistically examine

relationships between mercury concentrations in these 3 tissues. In all cases, mercury

concentrations were lowest in blood and highest in feathers.

We mapped the distribution of mercury concentrations in feathers of adults (Figure

8) and nestlings (Figure 9) by lakes to identify the source of mercury. Four water bodies

(Gulf, Kissimmee, Lochloosa, and Russell) had mean adult feather mercury concentrations

greater than 11 ppm (Figure 8, Table 7), although some individual nests at other lakes also

had adult feather mercury concentrations of > 11 ppm (Table 8). High adult feather

mercury concentrations were not consistently associated with any one lake or region,

although the Gulf (n =1) sample was the highest overall.

Mean bass mercury concentrations at lakes sampled by Ware et al. (1990) did not

correlate well with adult feather mercury concentrations (Figure 8). For example, lakes

associated with the Kissimmee River system had moderate levels of mercury in bass (0.5-

1.5 ppm) while feather mercury concentrations for adult eagles fell into all 3 categories.

We found a similar pattern with nestling feather mercury concentrations (Figure 9). The

fish data may not be directly comparable with our eagle data because samples were not

collected at the same time and they were not analyzed at the same laboratory; however,

the basic trends should remain the same. Consequently, sampling only fish populations




I.E


11

did not provide an accurate estimate of the trends in mercury concentrations in eagles in

this study. As mentioned earlier, Florida eagles have an extremely varied diet that includes

much non-fish prey, particularly wading birds. Consequently, we were not surprised to find

no relationship between eagle and bass mercury concentrations. We further examined

mercury concentrations in relation to the food-chain index developed from prey remains

found at nests.

We found prey remains in 22 of the 33 nests visited in 1993 (Tables 8 and 9),

representing 10 lakes. An ANOVA of mercury concentrations in blood and contour

feathers of nestlings at the 22 nests with prey remains did not indicate the positive

relationship with food-chain index that we had expected. The trend at 4 lakes, those with

greater than 2 nests per lake, is shown in Figures 10 and 11. Blood mercury

concentrations (Figure 10) at Lake Kissimmee and Orange Lake were significantly different

at some of the nests with varying food-chain indices, but concentrations were not

positively correlated with food-chain index. The correlation with blood at Lake Jackson

was negative, the opposite of expected. Feather mercury concentrations at Orange Lake

(Figure 11) were higher (E < 0.05) at the nest with the highest food-chain index; this

was the only positive correlation we observed. We might see a more consistent

relationship between mercury concentrations and food-chain index if data collected on prey

remains at each nest were more accurate.

Two other factors that can affect mercury concentrations are pH and trophic state.

In high pH, eutrophic systems, mercury is less available for uptake by living organisms

(Eisler 1987). Mercury concentrations in adult and nestling feathers were not correlated

with pH or trophic state index (TSI) using Pearson product-moment correlations (Table 10).

Mercury concentrations in nestling blood were correlated significantly with pH and TSI.

Low blood mercury concentrations were associated with higher pH, eutrophic systems. In








12

general, mercury concentrations in all samples were higher in mesotrophic systems than in

eutrophic systems (Table 11), although only nestling blood samples were significantly

different (Student's t-test: t=0.02, =0.01). Similarly, Ware et al. (1990) and Lange et

al. (1993) found lower mercury concentrations in bass in high pH, eutrophic systems. It is

possible that feather mercury concentrations did not show a significant correlation because

of a much greater variation in feather than in blood mercury concentrations.

Six museums provided feathers from the lower breast/upper abdomen of 20

specimens collected in Florida between 1885 and 1977 (Table 12). The mean

concentration of mercury detected was 43.5 mg/kg, which is significantly higher

(Student's t-test: t= 2.24, P=0.04) than the 9.08 mg/kg detected in adult feathers

collected 1991-1993. Highest mercury concentrations in the museum specimens occurred

in 2 birds collected near Tampa Bay (147.2 mg/kg, 296.2 mg/kg). Because these samples

were considerably higher than all others, we omitted them as outliers in another

comparison of past and present feather mercury levels. Even with these 2 outliers

omitted, however, we found a significant difference (Student's t-test: t= 2.93, E=0.009).

Museum feather mercury levels were 23.7 mg/kg as compared to 9.08 mg/kg in 1992 and

1993 feather samples. The data included past and present samples from 3 water bodies

(Figure 12). In all cases, past mercury concentrations were higher than present. Samples

obtained from eagles associated with Tampa Bay had highest past and present

concentrations.



SUMMARY AND RECOMMENDATIONS

Mercury concentrations in Florida eagles are above background levels, but lower

than those found in other populations. Studies on other bird species suggest that

concentrations in Florida eagles are below those that cause outright mortality but are







13

within the range of concentrations that can cause behavioral changes or reduce

reproduction. However, it has not been determined what effects these concentrations of

mercury actually have on behavior, reproduction or survival in eagles. Sublethal effects of

mercury on birds can include adverse effects on growth, development, reproduction, blood

and tissue chemistry, metabolism, and behavior (Eisler 1987). All of these sublethal

effects can make eagles more prone to other sources of mortality. Retarded growth or

development of nestlings, for example, might affect their survival. Wood (1992) found

that the older sibling in 2-chick nests had significantly higher survival, probably because it

monopolized food resources and became energetically fit more quickly. Thus, rapid

development appears to enhance survival.

Because mercury concentrations are increasing in the environment, we recommend

initiation of a monitoring program at specific nest sites to track changes in feather mercury

in eagles. Although feather mercury concentrations are more variable than those in blood,

feather and blood levels were significantly correlated. Mercury concentrations in feathers

of nestlings and adults are highly correlated, thus collecting adult feathers at nest sites will

be representative for adults and nestlings.









LITERATURE CITED

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bird feathers. Marine Poll. Bull. 15:22-24.

Bortolotti, G. R. 1984. Physical development of nestling bald eagles with emphasis on
the timing of growth events. Wilson Bull. 96:524-542.

Brezonik, P. L., W. C. Huber, and J. P. Heaney. 1982. A classification of Florida lakes.
Final Report, Florida Dept. Environ. Regulation, Tallahassee, Florida.

Canfield, D. E., Jr. 1981. Chemical and trophic state characteristics of Florida lakes.
Final Report, Coop. Fish and Wildlife Research Unit, University of Florida,
Gainesville, Florida.

Collins, H. H., Jr. 1981. Harper & Row's complete field guide to North American wildlife.
Harper & Row, Publishers, New York. 714pp.

Eisler, R. 1987. Mercury hazards to fish, wildlife, and invertebrates: a synoptic review.
U.S. Dept. Interior, Fish and Wildl. Service, Biol. Report 85(1.10). 90 pp.

Finley, M. T., W. H. Stickel, and R. E. Christensen. 1979. Mercury residues in tissues of
dead and surviving birds fed methylmercury. Bull. Envir. Contam. Toxicol. 21:105-
110.

Frenzel, R. W. and R. G. Anthony. 1989. Relationship of diets and environmental
contaminants in wintering bald eagles. J. Wildl. Manage. 53:792-802.

Furness, R. W., S. J. Muirhead, and W. Woodburn. 1986. Using bird feathers to measure
mercury in the environment: relationships between mercury content and moult.
Marine Poll. Bull. 17:27-30.

Heinz, G. H. 1979. Methylmercury: reproductive and behavioral effects on three
generations of mallard ducks. J. Wildl. Manage. 43:394-401.

Hord, L. J., M. Jennings, and A. Brunell. 1990. Mercury contamination of Florida
alligators. Pp. 229-240 in Crocodiles. Proc. 10th working meeting of the crocodile
specialist group, IUCN The World Conserv. Union, Gland, Switzerland. Vol. 1.
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Lange, T. R., H. E. Royals, and L. L. Connor. 1993. Influence of water chemistry on
mercury concentration in largemouth bass from Florida lakes. Trans. Am. Fisheries
Soc. 122:74-84.

Martin, A. C., H. S. Zim, and A. L. Nelson. 1951. American wildlife & plants. Dover
Publications, Inc., New York. 500pp.

Ohlendorf, H. M. 1993. Marine birds and trace elements in the temperate North Pacific.
Pp. 232-240 in Vermeer, K., K. T. Briggs, K. H. Morgan, and D. Siegel-Causey









(eds.), The status, ecology, and conservation of marine birds of the North Pacific.
Can. Wildl. Serv. Spec. Publ., Ottawa, Canada.

Royals, H., and T. Lange. 1990. Mercury in Florida fish and wildlife. Flor. Wildl. 44:3-6.

Solonen, T., and M. Lodenius. 1984. Mercury in Finnish sparrowhawks Accipiter nisus.
Ornis Fennica 61:58-63.

U. S. Fish and Wildlife Service. 1992. Status of contaminants in Maine eagles an
interim report. Fish and Wildl. Service Report FY92-NEFO-1-EC.

Ware, F. J., H. Royals, and T. Lange. 1990. Mercury contamination in Florida fish and
Wildlife. Proc. Ann. Conf. SE Assoc. Fish and Wildl. Agencies 44:5-12.

Wiemeyer, S. N., R. W. Frenzel, R. G. Anthony, B. R. McClelland, and R. L. Knight. 1989.
Environmental contaminants in blood of western bald eagles. J. Raptor Res.
23:140-146.

Wiemeyer, S. N., T. G. Lamont, C. M. Bunck, C. R. Sindelar, F. J. Gramlich, J. D. Fraser,
and M. A. Byrd. 1984. Organochlorine pesticide, polychlorobiphenyl, and mercury
residues in bald eagle eggs 1969-79 and their relationships to shell thinning and
reproduction. Arch. Envir. Contam. Toxicol. 13:529-549.

Wood, P. B. 1992. Habitat use, migration patterns, and survival rates of subadult bald
eagles in north Florida. Ph.D. dissert., Univ. of Florida, Gainesville. 123pp.


~ ~_~








Table 1. Mercury (Hg) concentrations (mg/kg) in potential prey of bald eagles in Florida.



Ha (ma/ka)
Prey type Tissue x Range


Wading birds'
large-fish eaters liver 1.39 0.18 74.5
small-fish eaters liver 0.73 0.12 5.38
small-fish/invertebrate eaters liver 0.64 0.05 5.38

Mottled duckb muscle 0.02

Largemouth bassb muscle 0.08 4.4
Bowfin, garb muscle 0.50 7.0


* Source: M.G. Spalding, University of
b Source: Ware et al. (1990).


Florida (unpublished data).












Table 2. Continued.


Nestling Adult
Water Body Nest Feather Blood Liver Feather Prey


Marion




Myakka

Orange




Parker

Phosphate b


Pierce

Russell


OS14
OS33
OS45A
OS51

SA17 d

AL17
AL24A
MR11
MRP

P049 d

PO40
PO15 d

PO82

OS85


Tohopekaliga OS31 1 1
OS36 2 2
OS54 2 2
OS72 2 2

Washington BE37 d 2 2 1

Wauberg AL40 2 2

Weohyakapka P098 2 2 1

Woodruff VO1 d 2

Subtotal (1993) 52 48 2 25 3


Total 61 57 2 33 3


* The water body is a natural lake, unless
b Pond in a reclaimed surface-mine.
C Gulf of Mexico, Tampa Bay Area.


indicated otherwise.


d Samples from nestlings treated at Florida Audubon Society, Birds of Prey Center.








Table 3. Mean mercury (Hg) concentrations (mg/kg) in tissues collected from nestling and
adult bald eagles at nests in Florida, 1991-1993.



Ha (ma/ka)
Tissue n x range


1991


all feathers


blood
contour feathers

contour feathers
all feathers



blood
liver
contour feathers

contour feathers
all feathers


12.30
10.95


2.12-9.60



0.23- 0.73
0.76-3.13


0.10-5.03



0.02 0.61
0.14-0.45
0.87- 14.30

4.70 34.70
4.00 34.70


1991-1993


blood
liver
contour feathers

contour feathers
all feathers


0.20
0.30
4.05

11.51
9.09


0.02 0.73
0.14-0.45
0.76-14.30

2.01 34.70
0.10 34.70


Adult


1992


Nestling


Adult




Nestling


Adult


Nestling


Adult








Table 4. Mercury (Hg) concentrations (mg/kg) from liver, feather, and blood samples of
recovered dead bald eagles in Florida and Georgia. Samples were supplied by the National
Wildlife Health Research Center, unless indicated otherwise.



Ha (ma/ka)
Year County City or Place Sex Age" Liver Feather Blood


Alachua
Alachua
Alachua
Alachua
Hernando
Highlands
Hillsborough
Lake
Manatee
Manatee
Marion
Monroe
Orange
Orange
Osceola
Osceola
Osceola
Osceola


Osceola
Osceola
Pasco
Pinellas
Polk
Polk
Polk
Polk
Polk
Polk
Sarasota
Volusia
Warren


Weeki Wachee Spring

Tampa

Parrish
near landfill
Belleville
Gulf of Mexico


Kissimmee
Nittaw
Interstate 75
Three Lakes WMA =


Kenansville



Lake Wales
Lake Wales
Frostproof

Lake Wales

in county landfill
Georgia d


* Age categories: adult (A); immature (I); nestling (N); subadult (S).
b Chemical analyses were not completed as of 12/30/93.
c Sample obtained from Florida Audubon Society, Birds of Prey Center.
d Sample obtained from Southeastern Raptor Rehabilitation Center.


1.01
2.38
5.43
0.35
0.21
5.10
0.63
b
1.51
4.82
b
3.15
0.86
2.32
b
b
b
1.77

12.20
7.00
0.30
1.04
1.40
4.44
1.97
1.07
3.11
0.95
2.84
b


7.26


1.35


0.85


13.70








Table 5. Mercury (Hg) concentrations (mg/kg) in bald eagle liver from carcasses collected
in Florida, 1987-1993.



Ha (ma/ka)
Age class n x range


Adult 12 3.61 0.63- 12.20

Subadult 4 1.61 0.86-3.11

Immature 5 2.91 0.35 4.82

Nestling 3 0.51 0.21 1.01


Total 24 2.74 0.21 12.20








Table 6. Mercury (Hg) concentrations (mg/kg) in tissues of bald eagles in Florida and from
other populations.



Ha (ma/ka)
Age" Tissue x Range Location Source


S CAPTIVE BIRDS

A Feathers
-artificial diet
-semi-natural diet


Blood


<0.1


0.80-3.80


0.23 0.17-0.31


Mich. Zoos
Mich. Zoos

Patuxent


E. Evans (pers. comm.)
E. Evans (pers. comm.)

Wiemeyer et al. (1989)


WILD BIRDS


A Feathers


Blood

AS Liver


N Feathers



Blood


8.10
9.09
21.90


0.10-34.70


1.76-2.96


1.89 0.92-3.90
2.74 0.21-12.2


4.05
9.30
9.47

0.20
0.23
0.23
1.20


0.76-14.30

1.13-33.29

0.02-0.73
0.01-1.10
0.07-0.65
nd b 4.20


0.30 0.14-0.45


Alaska
Florida
Great Lakes


Oregon

Oregon
Florida


Florida
Great Lakes
Maine

Florida
Maine
Washington
Oregon


Florida


E. Evans (pers. comm.)
Wood et al. (this study)
E. Evans (pers. comm.)

Frenzel & Anthony (1989)

Frenzel & Anthony (1989)
Wood et al. (this study)

Wood et al. (this study)
E. Evans (pers. comm.)
USFWS (1992)

Wood et al. (this study)
USFWS (1992)
Wiemeyer et al. (1989)
Wiemeyer et al. (1989)

Wood et al. (this study)


* Age categories: adult (A); adult and subadult (AS); nestling (N).
b Below detection limit of equipment (i.e., not detected).










Table 7. Mean mercury (Hg) concentrations (mg/kg) from bald eagles and their prey in Florida, and chemical characteristics of the
associated water bodies.


Adult Feather Ha Nestling Feather Ha Nestling Blood Ha Prey
Water Body Year n x Range n x Range n x Range Hgd pH TS' TSI


4.00-19.30


34.70



10.11 8.81-11.40


5.27-7.68


1.56-1.87





2.96-4.35

0.86-1.66

1.24-8.85


Cypress

George


Gulf 9

Harney

Jackson

Jessup

Kissimmee

Lochloosa

Marion

Myakka

Orange


Parker

Phosphate'

Pierce


0.76-1.70
2.09-8.78

2.15-2.38


5.85-5.86


0.16-0.20


0.06-0.07


0.06-0.24

0.03-0.05

0.10-0.26


0.07 0.06-0.08


0.27-0.73
0.02-0.25

0.07-0.10


0.13-0.18


0.74 M

E

8.37 E

0.63 7.92 M

7.37 E

0.05h 7.83 E

0.60 7.55 M

0.25 7.20 M
0.25 7.20 M

0.10 8.93 E

0.41'


7.79 M 59.0


2 0.43 0.38-0.49 0.08 E 64.2


1.97-4.35


7.29-16.10


4.70-17.60


12.16

19.80

8.04



5.03
9.08



8.84

7.07


5.07-13.90


7.09-10.60

5.59-8.55


2 12.55 10.80-14.30


Russell 93 1 13.9








Table 8. Continued.


Foodchain Feather Ha (ma/ka)
Water Body' Year Nest Index b Type c Feather x of Nest


Phosphate 93 P040 2.00 C 10.60 8.84
T 7.09

Pierce 93 P082 2.00 C 5.59 7.07
S 8.55

Russell 93 OS85 1.63 T 13.90 13.90

Tohopekaliga 92 OS54 C 2.01 0.76
P 0.10
S 0.17


SWater body is a natural lake, unless indicated otherwise.
b Average of all prey remains ranked by their position in the food chain (herbivore, first-
level carnivore, or higher-level carnivore) and weighted by habitat (terrestrial or aquatic). A
period indicates that prey remains were not found at that nest.
C Feather types collected: contour (C), primary (P), secondary (S), tertiary (T), and
unidentified (U).
d Gulf of Mexico, Tampa Bay Area.
* Pond in a reclaimed surface-mine.
'U. S. Fish & Wildlife Service (unpublished data).









Table 9. Mercury (Hg) concentrations (mg/kg) from individual nestling bald eagles in Florida. March and April 1992 and 1993.



Foodchain Ha (ma/ka)
Water Body Year Nest Index b ID Number" Feather Blood Liver


Cypress


George



Harney

Jackson



Jessup


Kissimmee


OS65

OS68


PU18
V029A


SE20

OS100
OS35
OS41

SE02


OS20

OS90
P078

P084
P087


Marion


OS33
OS45A
OS51


16993
16994
16995

16987
16991
16992

170

16823
16825
16824


16996
16997
16826
16818
16819
16809
16805
16806

16802
16803
16804


0.18
0.16
0.20

0.23
0.06
0.07


3.45

4.35
2.96
2.98

0.86
1.66

8.85
6.62
8.51
4.66
4.62
4.38
8.26
6.65

1.97
1.99
4.35


0.11
0.24
0.06

0.05
0.04

0.19
0.21
0.26
0.10
0.12
0.13
0.20
0.21

0.07
0.08
0.07


I








Table 10. Sample size (n), Pearson product-moment correlations (r), and probability of
significance (P) of lake pH and trophic state index (TSI) with mercury (Hg) concentrations
(mg/kg) in bald eagle tissues collected at nests in Florida, March and April 1992 and 1993.



pH TSI

Bald eagle tissue n r P n r P


Adult feathers 24 -0.32 0.12 27 -0.07 0.73

Nestling feathers 54 -0.10 0.48 58 -0.25 0.06

Nestling blood 51 -0.53 0.0001 56 -0.47 0.0003


Table 11. Mercury (Hg) concentrations (mg/kg) in blood and feathers of Florida bald
eagles from nests on eutrophic and mesotrophic systems, 1992 and 1993.



n x range


Adult feathers
Eutrophic 18 8.16 A 0.10- 19.80
Mesotrophic 9 9.21 A 5.03- 16.10

Nestling feathers
Eutrophic 32 3.53 A 0.85 14.30
Mesotrophic 28 4.65 A 0.76 10.70

Nestling blood
Eutrophic 30 0.16 B 0.04 0.48
Mesotrophic 26 0.26 A 0.02 0.73


* Means followed by the same letter
based on the Student's t-statistic.


within a pair are not significantly (P < 0.05) different,









Table 12. Mercury (Hg) concentrations (mg/kg) in lower breast/upper abdominal feathers of bald eagle museum specimens
that were collected in Florida.



Year County City or Place Water Body Sex Age Hg (mg/kg) Museum


1886 Tampa Bay F A 147.20 UMMZ
1887 Volusia Lake Harney M A 10.20 UMMZ
1888 Tampa Bay M A 296.20 UMMZ
1920 Alachua Alachua M A 15.50 UF
1924 Alachua Micanopy F A 10.70 UF
1926 Alachua Gainesville U A 6.34 UF
1928 Tampa Bay M I 29.00 UMMZ
1930 Alachua Gainesville M S 44.60 UF
1931 Alachua Gainesville U A 10.20 UF
1933 Polk Kissimmee Prairie U S 48.10 YPM
1935 b U S 17.60 AMNH
1935 b U S 29.20 AMNH
1939 Citrus Homosassa M A 23.50 UMMZ
1940 Lake Lake Hancock U S 22.60 YPM
1941 Citrus Ozello F A 15.10 UMMZ
1949 Glades F U 20.00 UM
1960 Alachua Orange Lake M A 91.00 UF
1963 Ocala Natl. For. M A 14.70 UF
1970 Alachua Evinston Orange Lake F A 10.90 UF
1977 Alachua Newberry M A 7.08 UWZ


* Museum abbreviations: American Museum of Natural History (AMNH); Florida
Miami (UM); University of Michigan Museum of Zoology (UMMZ); University of
University Peabody Museum (YPM).
b Collected prior to 1935 (exact date undetermined).


Museum of Natural History (UF); University of
Wisconsin Zoological Museum (UWZ); Yale


























WAS INGTON
PARKER
\ A CYPRESS
6SSELL JACK"ON
GU F PIERCE IARION
I E
WEOHYAKAPKA KISSI MEE




MYAKKA

Figure 1. Florida lakes and water bodies where samples were collected at bald eagle
nests, March and April, 1992 and 1993.


tqO













20- ADULT
n = 33 ALL FEATHERS
ADULT
>L 15 n = 13 CONTOUR FEATHERS






5 4
I I I 1 I I I





0 5 10 15 20 25 30 35
Hg (mg/kg)



Figure 2. Distribution of mercury concentrations (mg/kg) in tissues collected from nestling and adult bald eagles at nests in
Florida, March and April, 1992 and 1993.














-E


I *
r *
10o
.u*


5 5



00

0 II I I I imIn i i m
0 2 4 6 8 10 12 14
Nestling Feather Mercury (mg/kg)
J= outlier Inot used in correlation)


Figure 3. Pearson product-moment correlation between nestling and adult bald eagle feather mercury concentrations (mg/kg).
Feathers collected at Florida nests, March and April, 1992 and 1993.








A 1992 (n 9)
* 1993 (n = 48 )


AAA


330.6


E


0.4
0
0a
a,

S 0.2
0
C


**
0


**


. *


r Go
*I s'


Nestling Contour Feather (mg/kg)


Figure 4. Relationship between nestling bald eagle contour feather and blood mercury concentrations (mg/kg). Samples
collected at Florida nests, March and April, 1992 and 1993.


A








0.6


03
.9 0.5

E
t 0.4

a3
0
0 0.3-

D *
* *
S0.2
O0 *

0.1
0


0 2 4 6 8 10 12 14
Nestling Contour Feather Hg (mg/kg)



Figure 5. Linear regression of mercury concentrations (mg/kg) in nestling bald eagle contour feather and btood samples
collected at Florida eagle nests, March and April 1993.







8















2


1992 1993
ALl 7


1992
AL24A


1883 1992


FIgUr a. Mncury conentraio nrnlkg) in biwod and leaMhers of neslngf Florid bald arOW catel at th same nrwf in
1992 and 1993. Number above each bar indicates rfflmbr of n"lhgli-


1993


OS54


__


I s~a I
( FB~fhBr I










SBlood Liver n Feather


Lake
Washington


12



10



8

a"
a.
@ 6



4



2



0


Lake
Jackson
IMMATURE


Figure 7, Mercury concentrations Img/kg) in blood, liver, and feather tissues of 2 nestling,
a 2-year-old, and an adult bald eagle in Florida.


Osceola
County
ADULT


Lake
Parker


NESTLINGS







ADULT FEATHER HG


Hg (mg/kg)


M 5-11


, no data


Figure 8. Mean mercury concentrations (mg/kg) by lake for adult bald eagle feathers
collected at nests in Florida. Letters represent mean bass mercury concentrations (mg/kg):
L= <0.5; M=0.5-1.5.


=W5&a







NESTLING FEATHER HG


- 5-11


no data


Figure 9. Mean mercury concentrations (mg/kg) by lake for nestling bald eagle contour
feathers collected at nests in Florida. Letters represent mean bass mercury concentrations
(mg kg); L= <0.5; M 0.5-1.5.




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