USGS



BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

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Biological Characteristics 

Species

Anas rubripes is 48-56 cm in length. Males tend to have a greater average mass (1.4 kg) than females (1.1 kg) (Dunning, 1993). Its body is sooty brown with conspicuous white wing linings, and its bill is olive (Bull and Farrand, 1977).

Status in Estuaries

Though the black duck can be found breeding in a wide variety of forested and wetland habitats including marshes, lakes, streams, coastal mud flats and estuaries, wintering populations are confined to tidal marshes and open freshwater areas. This species can cover up to 13 square kilometers in establishing its home range. Black ducks are solitary nesters, and the availability of overhead protection provided by dense shrubs, hollow trees, small conifers or brush piles, appears to be the critical factor when selecting a nesting site (Bull and Farrand, 1977; Whitman and Castelli, 1995). Typical clutch size is 7-12 eggs laid in a nest of feathers and down. Young are precocial (Ehrlich et al., 1988). The maximum age of a black duck recorded from nature is 26 years (Clapp et al., 1982).

Abundance and Range

The black duck is widespread throughout eastern and central North America from Manitoba and Labrador south to Texas and Florida (Bull and Farrand, 1977). Less than 250,000 black ducks were surveyed on the Mississippi and Atlantic Flyways in 1995 (Whitman and Castelli, 1995), and in 1997 breeding black ducks on the Atlantic Flyway numbered 66,000 (Caithamer and Dubovsky, 1997). In eastern Canada south to Maine, 365,000 breeding ducks were counted in 1997 (Caithamer and Dubovsky, 1997).

Site Fidelity

The female will usually return to the area from which she was hatched, often the exact site (Whitman and Castelli, 1995).

Ease of Census

Difficult

Feeding Habits

Black ducks primarily feed by "tipping-up" in shallow water, but have also been known to graze and, when in deep water, dive as much as 10 feet (Clapp et al., 1982). The diet of the adult principally consists of sedges, rushes, grass, pondweed and duckweed. However, egg-laying females, molting adults, young broods, and ducks preparing for migration require an animal diet of small invertebrates and fish to provide high protein energy. Typical prey items include insects, snails, mussels, clams, minnows, and silversides.

Black Duck Contaminant Exposure Data

I.

Organochlorine Contaminants

A.

Concentrations in Wings

1.

Black duck wings were collected from New York and Pennsylvania in 1964 and analyzed in pools of 25 wings (Heath and Prouty, 1967). In New York, mean (range of pools) concentrations of DDT plus DDD were 1.05 (0.4-1.8) g/g wet weight in adults and 0.94 (0.2-2.2) g/g in immature ducks (young of the year). Concentrations in Pennsylvania were 0.53 (0.4-0.6) g/g in adults and 0.72 (0.4-1.1) g/g in immature ducks. Concentrations of DDE in New York were 1.08 (0.2-1.7) g/g in adults and 0.50 (0.2-0.9) g/g in immature ducks. In Pennsylvania, concentrations were 1.13 (0.5-2.0) g/g in adults and 0.78 (0.1-1.5) g/g in immature ducks. Mean dieldrin values were equal among age classes in both New York and Pennsylvania at 0.06 and 0.10 g/g, respectively, with concentrations ranging up to 0.20 g/g.

2.

In 1965 and 1966, wings of adult and juvenile black ducks were collected from hunters on the Atlantic Flyway (Heath, 1969). Concentrations of DDE in adults, calculated as individual state means, ranged from 0.30 g/g wet weight in South Carolina to 2.10 g/g in New Jersey. Concentrations in immatures ranged from 0.18 g/g in Vermont to 1.75 g/g in New Jersey. The means for the entire flyway were 1.23 g/g in adults and 0.75 g/g in immature ducks. New Jersey also had the highest mean concentration of DDT in both adults (0.78 g/g) and immatures (1.72 g/g), with lows below the limit of detection for ducks in Virginia and Vermont. Overall means were 0.33 g/g in adults and 0.46 g/g in immature. Mean values of DDD for both age classes were similar for all states and ranged up to 0.18 g/g, with the exception of Connecticut in which adults reached a mean concentration of 0.42 g/g. Flyway means were 0.12 g/g in adults and 0.11 g/g in immature ducks. Mean dieldrin levels were generally <0.12 g/g, with Connecticut again showing a high value of 0.53 g/g in immature ducks. Overall means were 0.05 g/g in adult and 0.11 g/g in immature ducks.

3.

Wings of adult black ducks were collected in 1969 from hunters on the Atlantic Flyway (Heath and Hill, 1974). Concentrations of DDE, calculated as individual state means, showed an overall increase from 1965-66 values to 1.42 g/g wet weight, with a range of 0.55 g/g in Maryland to 3.42 g/g in New Jersey. When segregated by sex, DDE concentrations in New York and New Jersey ducks tended to be higher in males than females. Analysis by site of collection also revealed higher DDE levels in birds from coastal counties than those from inland counties. DDT concentrations had an overall flyway mean of 0.12 g/g, with a high of 0.27 g/g in New Jersey, and all other states between 0.03 and 0.18 g/g. Mean levels of DDD were <0.09 for all states sampled, with an overall mean of 0.03 g/g. Mean dieldrin levels (0.14 g/g overall) were highest in Maine (0.44 g/g), North Carolina (0.30 g/g), and Rhode Island (0.26 g/g), and all other states <0.18 g/g. The flyway mean for PCBs was 1.20 g/g, with means ranging from 0.39 g/g in Maryland to 3.88 g/g in Connecticut.

4.

Wings of adult black ducks were collected in the fall and winter of 1972 from hunters on the Atlantic Flyway (White and Heath, 1976). Overall concentrations of DDE dropped significantly since 1969 to 0.35 g/g wet weight, and individual state means ranged from 0.12 g/g in Virginia to 0.77 g/g in New Jersey. DDT had an overall flyway mean of 0.07 g/g and state means ranging from 0.03-0.14 g/g. Mean concentrations of DDD were <0.06 for all states sampled, with an overall mean of 0.02 g/g. Mean dieldrin levels dropped significantly to 0.02 g/g with means for all states <0.08 g/g. The overall mean for PCBs was 1.36 g/g with a maximum concentration near 2.4 g/g in Massachusetts, Rhode Island, and New York. South Carolina had the lowest mean PCB concentration at 0.30 g/g. Heptachlor epoxide, HCB, and BHC were present in all samples at levels rarely exceeding 0.02 g/g and lindane was present in trace amounts in most of the samples.

5.

Wings of adult black ducks were collected during the 1976-77 hunting season on the Atlantic Flyway (White, 1979). DDE, detected in all samples, had an overall mean of 0.39 g/g wet weight, and individual state means ranging from 0.12 g/g in Rhode Island to 1.13 g/g in New Jersey. DDT and TDE, each detected in about 66% of samples, had means 0.11 g/g for all states. Dieldrin was detected in 84% of samples, with means 0.15 g/g for all states. The overall mean for PCBs, detected in all individuals sampled, was 0.52 g/g, with a high of 1.11 g/g in Connecticut and a low of 0.12 g/g in Vermont. The following substances were detected at levels <0.05 g/g: heptachlor epoxide (34% of samples), mirex (19%), endrin (3%), HCB (16%), and chlordane isomers (59%).

6.

Wings of adult black ducks were collected during the 1979-80 hunting season on the Atlantic Flyway (Cain, 1981). DDE, detected in all samples, had an overall mean concentration of 0.32 g/g wet weight, and individual state means ranging from 0.08 g/g in Connecticut to 0.67 g/g in Delaware. DDT, TDE, and dieldrin, detected in 38%, 29%, and 58% of samples, respectively, each had state means 0.11 g/g. The overall mean for PCBs, detected in all individuals sampled, was 0.63 g/g, and ranged from 0.15 g/g in North Carolina to 1.49 g/g in Connecticut. The following substances were detected at levels that seldom exceeded 0.1 g/g: heptachlor epoxide (4% of samples), mirex (13%), HCB (21%), and chlordane isomers (58%). Endrin was not detected in any samples.

7.

Wings of adult black ducks were collected during the 1981-82 hunting season on the Atlantic Flyway (Prouty and Bunck, 1986). DDE, detected in 95% of samples, had an overall mean of 0.19 g/g wet weight in both the northern and southern parts of the Atlantic Flyway. Individual state means ranged from none detected in Vermont to 0.48 g/g in West Virginia The overall mean for PCBs, detected in all individuals sampled, was 0.44 g/g in the northern flyway and 0.21 g/g in the southern flyway. State means ranged from 0.12 g/g in Vermont to 0.87 g/g in Massachusetts.

B.

Concentrations in Other Tissues of Adults and Juveniles

1.

Eight black ducks collected from New York state in 1979-80 were analyzed for PCB, DDE, and mirex in tissues (Kim et al., 1984). Concentrations of PCB ranged from 1.8-19 g/g wet weight in subcutaneous fat, 0.06-0.34 g/g in breast muscle, 0.45-1.0 g/g in liver, and 0.02-0.94 g/g in brain. DDE concentrations ranged from ND to 1.0 g/g in fat, and were <0.10 g/g in other tissues. Mirex was detected in the fat of one duck only at a concentration of 0.39 g/g and at concentrations 0.01 g/g in other tissues.

2.

In 1983-1984, black duck carcasses were collected from five regions of New York (Niagara Frontier, Finger Lakes, Eastern Lake Ontario to the St. Lawrence River, Hudson River to Lake Champlain, and Long Island) (Foley, 1992). PCBs were greatest in the Hudson River area at a mean of 7.8 g/g wet weight in fat and 0.11 g/g in muscle. Mean PCB values in all other areas ranged from 0.4-0.8 g/g in fat and ND-0.07 in muscle. Mean DDTr (DDT + DDE + DDD) concentrations were greatest on Long Island (3.613 g/g in fat and 0.05 g/g in muscle) and least in the Lake Ontario region (0.179 g/g in fat and none detected in muscle). DDTr means in the remaining areas ranged from 0.537-0.732 g/g in fat and 0.006-0.013 g/g in muscle. Long Island also had the greatest mean lipid concentration of dieldrin (142 ng/g) and Lake Ontario the least (18 ng/g), with other areas ranging from 32-36 ng/g. Mean lipid chlordane concentrations were greatest in Lake Ontario (801 ng/g) and Long Island (222 ng/g), with other regions ranging from 37-94 ng/g. HCB lipid means ranged from 6 ng/g (Lake Ontario) to 36 ng/g (Niagara Frontier).

3.

In 1988, four adult black duck brain and liver samples were collected from Benrock Swamp, South Australia (Falkenberg et al., 1994). Concentrations in the four samples were: <0.04 mg/kg dieldrin, <0.04 mg/kg DDD, <0.08 mg/kg DDE, and <0.04 mg/kg DDT.

4.

Seven black ducks were found either moribund or dead in Suffolk and Ontario counties in New York (Baker et al., 1976). PCB was detected in the liver only of two ducks at concentrations of 2.3 and 0.5 g/g, in the brain of one duck at 1.1 g/g, and in the liver (4.3 g/g), muscle (2.9 g/g), and brain (1.3 g/g) of another duck. All died of botulism.

C.

Concentrations in Eggs

1.

In 1964, black duck eggs were collected from 85 nests in nine states and Canada extending northward from Maryland along the Atlantic Flyway (Reichel and Addy, 1968). Mean state concentrations of DDE were 2.1 g/g for all states except New York, New Jersey, and Massachusetts which ranged from 4.4-5.5 g/g. These states also had the greatest mean concentrations of DDT, which ranged from 0.3-4.1 g/g overall. Maryland had the lowest concentrations of both DDE and DDT. DDD was detected in all states at concentrations 0.3 g/g, except Massachusetts (0.9 g/g) and New York (1.3 g/g). Dieldrin was also detected in eggs from all states sampled, with mean concentrations <0.5 g/g. Heptachlor epoxide was detected in trace amounts in about one-third of eggs collected. Eggs collected from New Jersey occurring in the same nest showed similar levels of organochlorines per egg in six of nine pairs analyzed.

2.

In 1971, 61 black duck eggs were collected from the northeastern United States and Canada (Longcore and Mulhern, 1973). DDE was detected in all eggs sampled, with the greatest mean concentrations in Delaware (5.940 g/g), New Jersey (1.971 g/g), New York (1.230 g/g), and Maine (1.013 g/g). DDD was detected in 31 of 61 eggs, and occurred at the greatest concentrations in New York (0.123 g/g) and Delaware (0.120 g/g). DDT concentrations, detected in 55 eggs, ranged from 0.025 g/g (Nova Scotia) to 0.420 g/g (Maine). Dieldrin was detected in 59 eggs, with mean concentrations ranging from 0.022 g/g in Vermont to approximately 0.120 in Delaware and Maryland. Heptachlor epoxide occurred in 46 eggs, with mean concentrations <0.040 g/g. PCBs were detected in 57 eggs with means ranging from 0.05 g/g in Nova Scotia to 3.30 g/g in Massachusetts. Mirex was not detected in any eggs.

3.

In 1977, three black duck eggs were collected from Spider, Hog, and Pilot Islands near Door County, Wisconsin in Lake Michigan (Haseltine et al., 1981). PCB residues, detected in all eggs, ranged from 0.71-6.7 g/g wet weight, with a geometric mean of 2.2 g/g. DDE was also detected in all samples and ranged from 0.21-2.5 g/g, with a geometric mean of 0.77 g/g. No other organochlorines were detected.

4.

In 1978, 49 black duck eggs were collected from the Atlantic Flyway (Haseltine et al., 1980b). DDE was detected in 39 eggs at a mean concentration of 0.65 g/g wet weight. Mean concentrations ranged from ND in Virginia and New Brunswick to 2.0 g/g in Delaware. DDT was detected only in Delaware and Rhode Island (5 eggs total) at a range of 0.09-0.17 g/g. TDE was detected at levels of 0.10-0.15 g/g in a total of four eggs from Delaware, Maine, and Quebec. PCBs resembling Arochlor 1260 were detected in 24 eggs with means up to 1.3 g/g in Rhode Island. PCBs were not detected in eggs from Virginia, Maryland, Pennsylvania, or Nova Scotia. Dieldrin was detected in one egg from Delaware (0.09 g/g) and one egg from Massachusetts (0.17 g/g). Heptachlor epoxide occurred in a single egg from Rhode Island (0.14 g/g). Oxychlordane was detected in five eggs from four states at levels ranging from 0.05-0.16 g/g. No other organochlorines were detected.

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

A.

Concentrations in Tissues of Adults and Juveniles

1.

From 1937 to 1950, 1162 black duck gizzards from many parts of the United States were analyzed for Pb shot (Bellrose 1951). Of these gizzards, 7.92% contained Pb shot (5.34% had one shot, 0.77% had two shot, 0.87% had three shot, 0.26% had four shot, 0.34% had six shot, and 0.35% had more than six shot).

2.

Two black ducks from the east coast contained hepatic Pb concentrations of 0.4 and 0.6 g/g wet weight (Bagley and Locke, 1967).

3.

Wings of adult black ducks were collected in 1969 from hunters on the Atlantic Flyway (Heath and Hill, 1974). The mean concentration of Hg for all states was 0.19 g/g wet weight, with state means ranging from 0.11 g/g (Maryland) to 0.33 g/g (New York).

4.

In November 1970, five female black ducks were collected from the Lake Champlain vicinity in Vermont (Baskett, 1975). Mercury concentrations in breast muscle were 0.04 and 0.09 g/g wet weight in two immature ducks and 0.06, 0.17, and 0.23 g/g in three adults.

5.

Black ducks were collected in 1970-71 from 21 sites in eastern Canada where high hunter pressure and Hg contamination were known or suspected (Pearce et al., 1976). Breast muscle analyzed from 45 specimens revealed Hg concentrations ranging from 0.01 to 0.43 g/g wet weight, and one specimen at 1.05 g/g. Wing muscle from eleven sites contained mean Hg concentrations of 0.08 to 0.26 g/g. The concentration of Hg in wing muscle to breast muscle showed a highly significant relationship with a ratio of 1.09.

6.

A total of 270 immature and 45 adult black duck wings from the Atlantic Flyway were selected from 1972 and 1973 wing survey collections submitted by hunters for determination of Pb exposure (Stendell et al., 1979). Mean Pb concentrations were 8.1 g/g dry weight in immature ducks and 7.7 g/g in adults. State means ranged from 5.2 g/g in Maine to 13.2 g/g in Virginia. Concentrations of Pb >20.0 g/g were found in 9.6% of immatures and 8.9% of adults. No adults and just 0.7% of immatures contained <0.5 g/g Pb.

7.

Seven black ducks were found either moribund or dead in Suffolk and Ontario counties in New York State (Baker et al., 1976). Lead was detected in only the liver of three ducks (concentrations of 5.76, 6.96, and 2.0 g/g), and only in the muscle of two ducks (2.0 and 7.01 g/g). Mercury was found in the liver only of two ducks at 0.152 and 0.030 g/g, and in liver and muscle of two ducks at 0.284 and 0.092 g/g, respectively, for one specimen, and 0.031 and 0.084 g/g for the second specimen. Cadmium, Be, and As were not detected in either organ of any samples. All died of botulism.

8.

Primary flight feathers of 16 immature and adult black duck wings were collected from hunters in Ontario and northern Saskatchewan hunters in 1975 (Ranta et al., 1978). Zinc concentrations ranged from 113-149 g/g dry weight. Copper and Ni residues for 15 of the 16 ducks ranged from 9-24 g/g and 0.2-12.5 g/g, respectively. A single black duck, which was suspected to be collected outside its original natal area, had elevated concentrations of Cu (53 g/g) and Ni (36.7 g/g). Copper and Ni values tended to be higher near Sudbury, Ontario, reflecting known particulate fallout. No trends were observed in sex, age, or choice of wing analyzed.

9.

From 1976 to 1980, black duck gizzards were collected from Merrymeeting Bay, Maine (Longcore et al., 1982). Of 506 ducks sampled, 6.9% contained Pb shot in the gizzard and one duck contained steel shot. The greatest percentage of ducks with shot in the gizzard (11%) occurred in 1976 and 1978. The lowest percentage (3%) occurred in 1979. Lead shot in the bottom sediments averaged 99,932 shot/ha. Of methods used to count shot in the gizzards, visual examination and x-ray produced equivalent accuracy, while fluoroscopic x-ray proved unsatisfactory.

10.

From 1976 to 1980, tissues of up to 128 black ducks were collected from the Chesapeake Bay (Di Giulio and Scanlon, 1984). Mean (range) Cd levels were 1.16 (<0.10-11.75) g/g dry weight in the liver and 11.49 (1.05-37.89) g/g in the kidney. Mean Pb levels were 12.4 (<0.5-302.4) g/g in the liver, 17.6 (<0.5-35.8) g/g in the kidney, and 5.6 (0.8-19.5) g/g in the ulnar bones. Lead shot occurred in the gizzards of 23 of 128 ducks sampled (18.0%) (see Scanlon et al., 1980). Mean Zn concentrations were measured at 136 (29-495) g/g in the liver, 84 (57-120) g/g in the kidneys, and 117 (81-136) g/g in the ulnar bones. Mean Cu levels were 34.9 (1.5-235.4) g/g in the liver and 14.2 (4.9-29.6) g/g in the kidneys.

11.

From 1976 to 1980, black duck gizzards and livers were collected from Maryland hunters for determination of Pb concentrations (Scanlon et al., 1980). Lead shot was detected in 23 gizzards, with corresponding livers containing a mean Pb concentration of 36.8 g/g dry weight. Twelve ducks contained hepatic concentrations >10 g/g. Mean Pb concentrations (11.4 g/g) were significantly lower in 82 ducks with no Pb shot detected in the gizzard. Concentrations in 8 of these ducks were >10 g/g.

12.

During the 1977-1979 hunting seasons, black duck gizzards were harvested from state management areas in Indiana and ingested pellets of Pb and steel were counted both manually and radiographically (Sporre and Blevins, 1981). Of 188 gizzards collected, the frequency of those containing Pb shot only was 13 when measured manually and 15 when measured radiographically. Both methods detected one gizzard that contained steel shot only and one gizzard that contained both types of shot. In all, 9.0% of ducks held some kind of shot in their gizzard over the three year period. The percentage of ducks with shot varied from 7.7% in the 1977-78 hunting season, to 12.6% in 1978-79, to 5.7% in 1979-80.

13.

Black ducks collected from the lower Chesapeake Bay region contained mean concentrations of 15.3 g/g dry weight Cd and 3.0 g/g Pb in the kidney, and 6.5 g/g Pb in bone (Di Giulio and Scanlon, 1981).

14.

Liver samples from six adult ducks collected from the Raritan Bay estuary in northeastern New Jersey contained Cd levels ranging from 0.254 to 0.385 g/g wet weight (Gochfeld and Burger, 1982). Food items found in the stomach of two ducks contained Cd levels ranging from 42-60 g/g.

15.

From December 1980 to January 1981, black ducks were collected from hunters in Raritan Bay, New Jersey (Burger and Gochfeld, 1985). Concentrations of nine heavy metals were tested in the salt gland of six ducks and the liver of fourteen ducks. Only Hg concentrations were significantly higher in the liver (525 ng/g wet weight) then the salt gland (152 ng/g). Metals that had significantly higher mean concentrations in the salt gland were Co (341 ng/g liver, 4291 ng/g salt gland), Cr (2051 ng/g liver, 18,903 ng/g salt gland), Cu (8508 ng/g liver, 26,125 ng/g salt gland), and Ni (1547 ng/g liver, 15, 198 ng/g salt gland). Four metals showed no significant differences between organs: Cd (518 ng/g liver, 642 ng/g salt gland), Pb (601 ng/g liver, 500 ng/g slat gland), Mn (1848 ng/g liver, 2499 ng/g salt gland), and Zn (40,563 ng/g liver, 33,208 ng/g salt gland).

16.

From December 1980 to January 1981, six female and eight male black ducks, in concert with samples of scaup and mallards, were collected from hunters in Raritan Bay, New Jersey to test for the influence of sex and species on heavy metal concentrations in the liver (Gochfeld and Burger, 1987). Male black ducks contained significantly higher mean values of Cu (10,604 ng/g wet weight), Mn (2283 ng/g), and Zn (50,014 ng/g) then females (5715 ng/g, 1268 ng/g, and 17,963 ng/g, respectively). No difference between sexes was determined for other metals tested: Cd (333 ng/g female, 565 ng/g male), Co (248 ng/g female, 411 ng/g male), Cr (2048 ng/g female, 2053 ng/g male), Pb (467 ng/g female, 703 ng/g male), Hg (588 ng/g female, 478 ng/g male), and Ni (1023 ng/g female, 1938 ng/g male). Male body weight was significantly greater than that of females. Interspecies studies showed that black duck livers contained significantly less Cu and Mn than scaup livers, and less Zn than mallard livers.

17.

Two black ducks were collected in 1980 and 1981 from Catahoula Lake, Louisiana, as part of a larger waterfowl collection (Zwank et al., 1985). One of the two gizzards contained Pb shot and the mean hepatic Pb concentration for both ducks was 126.5 g/g dry weight.

18.

The gizzard and liver of mallards and black ducks killed by hunters in Pennsylvania were collected during the 1980-81 hunting season (Calle et al., 1982). Approximately 20% of the sample were black ducks. The combined results for mallards and black duck showed that 11.2% of birds contained either Pb or steel in the gizzard, 5.6% contained Pb alone, 6.3% contained steel alone, and 0.7% contained both types of shot. Six of the 23 ducks that carried Pb shot also had hepatic Pb concentrations considered to be toxic ( 6.0 g/g wet weight). Only 2 of 386 ducks without Pb shot had toxic concentrations. Hepatic concentrations ranged from <1 g/g to 21 g/g.

19.

From 1986 to 1988, 435 black ducks wintering in two refuges in northwestern Tennessee were tested for evidence of Pb exposure ( 0.2 g/g blood Pb) (Samuel et al., 1992). Overall, 11.7% of birds were determined to have been exposed to Pb, with adults having a significantly greater incidence of exposure. At Tennessee National Wildlife Refuge, 12.4% of adults and 8.6% of juveniles tested positive for exposure. At Cross Creeks National Wildlife Refuge 17.6% of adults and 5.0% of juveniles were categorized as Pb-exposed, and survival rates to one year were lower than Tennessee National Wildlife Refuge. No significant differences in blood Pb levels were found between refuge, year, or sex of bird.

20.

During 2 periods, 1986-1989 (n=435) and 1997-1999 (n=721), black ducks were tested for Pb exposure in northwestern Tennessee (Samuel et al., 2000). From the first period, 11.7% of birds had blood Pb concentrations >0.2 g/g indicating exposure. 17.6% of adults and 5.0% of juveniles were categorized as Pb-exposed. In the second period, 6.5% had Pb values >0.2 g/g. 5.3% of adults and 8.3% of juvinile birds were considered exposed. No significant differences in blood Pb levels were found between refuge, year, age, or sex of bird.

21.

In 1988-89, black ducks were collected from hunted and unhunted marshes in Nova Scotia and Prince Edward Island (Daury et al., 1993). In unhunted marshes, blood Pb concentrations tended to be <30 ng/g. In hunted marshes in Nova Scotia, of 139 ducks collected prior to the hunting season, 7.2% had blood Pb concentrations that were >100 ng/g and 5.0% had levels >200 ng/g. On Prince Edward Island, of 50 sampled ducks, 42.0% and 28.0%, respectively, had similarly elevated levels.

22.

From 1988 to 1991, 815 black duck wings and gizzards were collected from hunters in Nova Scotia and Prince Edward Island (Daury et al., 1994). Lead shot was found in the gizzards of 43 birds, or 5.3%, in the following amounts: 26 contained one pellet, 7 contained two pellets, 3 contained three pellets, 1 contained four pellets, 5 contained five pellets, and 1 gizzard contained >five pellets. The incidence of gizzards containing shot was similar between locations, with Nova Scotia totaling 4.6% and Prince Edward Island at 7.1%.

23.

In 1988 and 1989 juvenile black ducks were collected from hunters in eastern Canada (Scheuhammer and Dickson, 1996). Black ducks with Pb shot in the gizzards had a significantly greater incidence of elevated Pb in the bone than ducks without shot. All ducks with shot present in the gizzard had concentrations >10 g/g dry weight in bone, whereas only 30% of those without shot attained such levels. Data were combined with that of mallards and analysis revealed that concentrations of Pb detected in the bone increased in areas with increased hunting, though two of nine smelters in the study area also occurred in heavy hunting areas making their effects difficult to assess.

24.

Sediment ingestion was analyzed in nine black ducks collected from the Prime Hook National Wildlife Refuge in 1995 and 1996 (Beyer et al., 1999).  Sediment content in digesta was estimated at 1.4%, slightly lower than other dabbling ducks studied.  Concentrations of Pb in digesta were positively correlated with sediment ingestion after one duck containing Pb shot was removed from the analysis.  These results imply that in the absence of Pb shot ingestion, Pb exposure for this species occurs primarily from sediment ingestion and not food items.

B.

Concentrations in Eggs

1.

In 1977, Hg concentrations ranged from 0.06-0.19 g/g wet weight in three black duck eggs collected from Spider, Hog, and Pilot Islands in Lake Michigan near Door County, Wisconsin (Haseltine et al., 1981).

2.

In 1978, 49 black duck eggs were collected from the Atlantic Flyway (Haseltine et al., 1980b). Mercury was detected in 31 eggs with an overall mean of 0.11 g/g wet weight. No Hg was detected in eggs from New Brunswick, Maryland, or Virginia. Chromium and Cu were detected in all eggs analyzed for heavy metals (20), at means of 0.64 and 1.68 g/g, respectively. Arsenic was present in 18 eggs at an mean concentration of 0.18 g/g.

IV.

Petroleum

 

No residue data available  

 

Black Duck Contaminant Response Data

I.

Organochlorine Contaminants

A.

Eggshell Thinning and Reproduction

1.

In 1969, black ducks were fed diets supplemented with 0, 10, or 30 ppm DDE before eggshells were examined for thinning and mineral content (Longcore et. al, 1971a). Concentrations of Ba and Sr were significantly lower than controls in both treatment groups, and concentrations of Mg were significantly higher. In shells from DDE-treated ducks, the percentage of calcium tended to be lower and the percentage of Na and Cu tended to be higher. In the control group, higher levels of Mg and Na were associated with thinner eggshells.

2.

Reproductive effects were studied in the aforementioned experiment (Longcore et. al, 1971a) in which black ducks were fed diets supplemented by 0, 10, or 30 ppm DDE (Longcore et al., 1971b). Eggshells from ducks in experimental groups were 18-24% thinner at the equator, 28-31% thinner at the cap, and 29-38% thinner at the apex than eggshells from undosed ducks. Cracked eggshells (hairline cracks, indentations, collapse at egg poles), which were significantly thinner than uncracked shells from the same dosage group, rose from 2% in controls to 10% in the 10 ppm group to 21% in the 30 ppm group. Egg production did not differ significantly between groups, though two of twelve hens in the 30 ppm group failed to lay eggs. Embryonic mortality in dosed birds was significantly greater than controls in each of the first two weeks of incubation. Survival of ducklings to 21 days was 40-76% lower in the treatment groups. Average DDE residues in eggs were <0.7 g/g wet weight for undosed ducks, 46 g/g for the 10 ppm group, and 144 g/g for the 30 ppm group. Residues of DDT, DDD, and dieldrin were <0.05 g/g for all eggs.

3.

Eggshells from two-year old black ducks fed 10 ppm DDE were thinner by 21.7% at the equator, 30.0% at the cap, and 32.9% at the apex than shells from undosed ducks (Longcore and Samson, 1973). Shell weight dropped 25% from 0.0693 gm/cm2 in controls to 0.0522 gm/cm2 in treated birds. The number of cracked shells was similar to controls on the day laid, but increased significantly during establishment of the clutch, incubation, and the total nesting period. No eggs of control ducks disappeared, but ducks fed DDE experienced a 42% disappearance rate of eggs, all of which were cracked and most of which were found in the water troughs. DDE-treated hens laid more eggs than controls but had a hatching rate of only 19% (compared to 86% in controls) and a 3-week survival rate of 0.6 young per hen (compared to 3.0 in controls). DDE concentrations averaged 64.9 g/g wet weight in eggs of treated ducks, PCBs averaged 0.44 g/g and DDD, DDT, and BHC levels did not exceed 0.28 g/g.

4.

In 1971, shell thickness was measured of 61 black duck eggs collected from the Northeastern United States and Canada (Longcore and Mulhern, 1973). Average thickness of fresh eggs plus those incubated less than one week (N=52) was 0.343 mm, representing a 1.4% thinning from comparable pre-1939 values. Those incubated longer than one week (N=9) averaged 0.349 mm. Thickness of all shells at the equator ranged from 0.30-0.40 mm, with an average of 0.344 mm. Shells were significantly thicker than a comparable survey performed in 1964 in which organochlorine residues were higher.

5.

Black ducks placed on a 0, 10 or 30 ppm DDE supplemented diet for two breeding seasons (see Longcore et al., 1971a and 1971b) were maintained on untreated diets for two years after cessation of treatment (Longcore and Stendell, 1977). Half of the birds (6 treated and 8 untreated) died throughout the course of the study, though mortality could not be conclusively linked to DDE. For treated birds, mean carcass DDE concentration dropped from 151.5 g/g wet weight for males and 159.6 g/g for females during treatment to 12.2 and 3.4 g/g, respectively, 24 months after treatment ended. Though concentrations in eggs also dropped, DDE residues in treated birds remained at 6.2 g/g 24 months after treatment compared to 0.36 g/g in controls. Shell thickness was approximately 20% below that of controls during the first three years of study and 10% below during the final year. Analysis showed that thickness increased as values of DDE decreased. Though clutch size and hatchability was similar between groups, overall productivity was lower in treated groups (47%) than control groups (69%) when comparing the number of birds surviving to three weeks of age.

6.

In 1970-72, 20 pairs of black ducks were placed on a diet supplemented by 3 ppm dry weight DDE (Longcore and Stendell, 1982). Mean eggshell thickness was not different from that of controls, but shell weight was reduced by 11.3% and the thickness index was reduced by 9.6%. Contaminants present in eggs from treated birds were DDE (17.9 g/g wet weight), DDT (1.26 g/g), PCB (1.3 g/g) and trace amounts of DDD and dieldrin.

7.

In 1978, mean shell thickness in 49 black duck eggs collected from the Atlantic Flyway was 0.345 mm, with a range of 0.279-0.389 mm (Haseltine et al., 1980b). When eggs more than one week developed were eliminated from the analysis, the resulting thickness was 0.347 mm. This value is equal to the thickness of comparable eggs collected from before 1946.

B.

Behavioral, Biochemical and Morphological Responses

1.

Pairs of black ducks were fed a duck breeder mash containing either 0, 10, or 50 ppm toxaphene three months before egg laying (Heinz and Finley, 1978). Upon hatching, young were fed toxaphene at the same level as their parents and tested for avoidance of a freight stimulus at 5 days of age. No significant difference in avoidance behavior was found between groups.

2.

Pairs of black ducks were fed breeder mash containing either 0, 10, or 50 g/g toxaphene three months prior to egg laying (Mehrle et al., 1979). No mortality occurred as a result of toxaphene ingestion and only males in the 50 g/g showed a significant decrease in weight. Growth of hatchlings showed significant decreases in the 50 g/g group and significant increases in the 10 g/g group, but weight was normal for all groups after the 42-day measurement. Female ducklings experienced impaired backbone development, with decreased collagen in the cervical vertebrae in the 50 g/g group and increased calcium concentration in the vertebrae of the 10 and 50 g/g groups. Tibia development was not impaired. Carcass toxaphene residues averaged slightly less than dietary levels.

3.

Pairs of black ducks were fed breeder mash containing either 0, 10, or 50 ppm toxaphene over the course of two breeding seasons (Haseltine et al., 1980a). No adults died as a result of toxaphene ingestion. Males experienced a reduction in weight, but only during the summer months. Both groups of treated females had larger livers then controls by the end of the second breeding season and males in the 50 ppm group had elevated brain weights. Egg-laying differed among groups only in that hens fed 50 ppm tended to lay eggs later in the season and initiate incubation faster. Clutch size, hatching success, and eggshell thickness was not effected. Ducklings in the 50 ppm group tended to show slightly lower weight gain and survival rates, and hatching success was greater in the second breeding season for this group. Toxaphene residues in the carcass of the adults and young averaged 50-100% of dietary concentrations. Liver residues were found in all birds and brain residues found in only one duck in the 10 ppm group and most in the 50 ppm group. Residues in both tissues rarely exceeded 0.5 g/g wet weight.

4.

One year old black ducks were provided a diet containing organochlorine mixtures for ten days either in low doses (0.5 ppm endrin, 3 ppm heptachlor, 10 ppm Arochlor 1254) or high doses (5 ppm endrin, 30 ppm heptachlor, 10 ppm Arochlor 1254) and sacrificed (Hall et al., 1989). Birds on both diets fed well, maintained normal body weight, and appeared healthy throughout the feeding trial. Residue levels were determined for the carcass, fat, and wing according to sex. Males and females showed similar residues in the low dose group, but males tended to have higher residues than females in the high dose group. Comparisons between tissues tended to be similar though endrin levels were greater in the wing and less in the carcass, and Arochlor 1254 appeared less in the wing and more in the fat. Heptachlor and Arochlor 1254 showed a high level of reliability in predicting levels in one tissue based on another, while predictions for endrin proved less reliable.

II.

Cholinesterase-Inhibiting Pesticides

1.

Several specimens were found dead on an estate lawn in New York state in 1970 (Stone 1979).  The ducks had been fed cracked corn, in an area treated with 1 lb/1,000 sq ft diazinon.

2.

Groups of twenty adult black ducks maintained on either saltwater or freshwater for eleven days were split in half on day six to create treatment groups in which diets were supplemented by 17 ppm fenthion (Eastin et al., 1982). Ducks maintained on saltwater, as opposed to freshwater, had the following effects regardless of fenthion intake: reduced body weight, increased levels of plasma uric acid and osmolality, heavier salt glands, and increased mean plasma Na levels. Hematocrit levels decreased over time in ducks fed freshwater and were also not affected by fenthion intake. Birds on the saltwater plus fenthion diet had greater protein concentration but reduced mucosal protein concentration compared to freshwater controls. Plasma ChE activity became reduced two days after the introduction of fenthion in both treatment groups and by the fifth day was lowered by 33% in the freshwater group and 23% in the saltwater group. Salt gland ChE was reduced by 26% in the saltwater treatment group compared to either of the control groups. Salt gland Na,K-ATPase activity was significantly increased in birds given saltwater, but the increase in salt gland Na,K-ATPase activity was blunted in those receiving saltwater and fenthion. Mg-ATPase activity in the intestinal mucosa was reduced in birds receiving freshwater plus fenthion compared to groups not exposed to fenthion.

3.

Eight treatment groups were created of three-month old black ducks maintained for 12 days on either freshwater (FW), saltwater (SW), or FW then SW, and fed untreated diets or diets supplemented with 21 ppm fenthion on days 1-7 or days 7-12 (Rattner et al., 1983). Body weight, hematocrit, salt gland weight, plasma osmolality, concentrations of Na+ and K+ in brain supernatant, and salt gland Na+,K+-ATPase activity were all increased in birds exposed to SW during the trial regardless of fenthion exposure. Brain ChE activity of birds receiving fenthion was inhibited 44-52% in SW groups and 61% in the FW group receiving the organophosphate on days 7-12. Recovery of ChE levels was observed after termination of fenthion treatment. Salt gland ChE inhibition of groups given fenthion was 14-26% in SW groups and 36% in the FW group. Plasma Na+ and Cl- levels increased in SW groups, though ingestion of fenthion for 6 days may have blunted the rise. Plasma ChE activity was inhibited by 86-96% following fenthion ingestion, but had risen back to control levels 6 days after treatment had ended.

4.

In 1980-81, a small shallow pond in Maine was aerially sprayed with carbaryl at the standard application rate of 840 g active ingredient/ha (Hunter et al., 1984). Human-imprinted black duck ducklings placed on the pond from dawn until dusk gained less weight on a daily basis than ducklings placed on a control lake, possibly due to a significant post-spraying decrease in invertebrate biomass on the experimental pond. After spraying, the percent of time spent searching for food increased in experimental ducklings and decreased in controls. Rate of movement was also shown to increase in experimental ducklings.

5.

An application of the organophosphate diazinon sprayed on a lawn in New York was associated with the deaths of 100 black ducks and mallards (Stone and Gradoni, 1985).

III.

Trace Elements, Metals, and Metalloids

1.

From 1948 to 1954, black ducks collected from the lower Detroit River were weighed and fluoroscoped to determine the number containing Pb shot (Hunt, 1960). Of 2007 live-trapped ducks, 117 contained ingested shot in the gizzard in the following amounts: 4.9% of the total number of gizzards held 1 shot, 0.5% held 2 shots, 0.2% held 3 shots, and 0.2% held >3 shots, for a total of 5.8% with shot. The average weight of males was 2 lbs 15.4 oz for those containing shot and 3 lbs 0 oz for those without shot. Females averaged 2 lbs 9.7 oz with shot and 2 lbs 9.6 oz without. Longevity, defined as the length of time a duck lived after banding before being recovered dead or alive, was calculated as 1.42 years for both ducks containing lead and those without. Of 1533 black ducks shot at the Pte. Mouillee State Game Area, 73, or 4.8%, contained Pb shot.

2.

In 1966, an adult male black duck collected at Rehoboth Bay was determined to have died from Pb poisoning (Locke and Bagley, 1967). Two worn Pb shot were found in the gizzard and Pb concentrations were 25 g/g wet weight in liver and 5 g/g in brain. The bird was extremely emaciated, had thin shrunken pectorals, and was stained with a greenish diarrhea. Internal examination revealed no fat, a slightly enlarged gall bladder, and a shrunken spleen and liver (13.5 grams). The kidney was found to have undergone a fair amount of autolysis though typical acid-fast intranuclear inclusion bodies were found in the cells of the proximal convoluted tubules.

3.

In 1968, a group of pen-reared male black ducks dosed with eight No. 6 Pb shot all died within 19 days, with an average time until death of 9 days (Longcore et al., 1974).

4.

In 1969, black ducks were fed diets supplemented with 0, 10, or 30 ppm DDE before eggshells were examined for thinning and mineral content (Longcore et. al, 1971a). Concentrations of Ba and Sr were significantly lower than controls in both experimental groups, and that of Mg was significantly higher. The percentage of calcium tended to be lower and the percentage of Na and Cu tended to be higher in shells from DDE-treated ducks. In the control group, higher levels of Mg and Na were associated with thinner eggshells.

5.

For two breeding seasons beginning in 1972, thirteen pairs of captive black ducks were placed on diets containing 3 ppm Hg approximately three months before laying and lasting a total of 28 weeks (Finley and Stendell, 1978). No mortality or weight change occurred among adults but reproductive effects were evident. Compared to controls, fewer treated hens laid and incubated eggs, and clutch size, egg production, and number of eggs incubated were lowered. Most severely effected were hatchability and duckling survival, as most progeny died during the final week of incubation or the first week after hatching. Before death, ducklings exhibited tremors and loss of co-ordination, and histological examination revealed brain abnormalities including demyelination, neuron shrinkage, excessive necrosis, and a Hg concentration between 3.25 and 6.98 g/g wet weight. Hg residues in eggs, embryos and ducklings averaged about 30% lower during the second breeding season, with mean values in embryos that failed to hatch falling from 9.62 to 6.08 g/g. Adults birds had the greatest concentration of Hg in the feathers, followed by the liver, kidney, breast muscle, and brain. Lesions characteristic of methyl mercury poisoning were not found in adults.

6.

Young, pen-reared black ducks (11 to 17 days old) were tested for absorption rates of five Cr compounds by use of an in vivo intestinal perfusion technique (Elastin et al., 1980). Chromium was absorbed from saline solutions of KCr (SO4)2 and CrO3 at a rate that was approximately 1.5 to 2.0 times greater than from solutions of Cr, Cr(NO3) 3, and Cr(C5H7O2) 3, suggesting that the ionic form of Cr in solution may an important factor in determining absorption from the small intestine.

7.

Pairs of black ducks were fed a duck breeder mash containing 0, 20, or 200 ppm Cr five months before egg laying (Heinz et al., 1981). Upon hatching, young were fed Cr at the same level as their parents and tested for avoidance of a freight stimulus at 7 days of age. No significant difference in avoidance behavior was found between groups.

8.

Pairs of black ducks were fed 0, 4, or 40 ppm Cd in the form of cadmium chloride four months before egg laying (Heinz et al., 1983). Upon hatching, young were fed Cd at the same level as their parents and tested for avoidance of a fright stimulus. Ducklings fed 4 ppm Cd ran twice as far from the stimulus than either controls or those fed at concentrations of 40 ppm.

9.

For six weeks, pairs of black ducks fed a duck breeder mash containing 0, 25, 100, 400 or 1600 ppm powdered U showed few adverse affects to treatment (Haseltine and Sileo, 1983). One duck in the 100 ppm group died in the sixth week after experiencing weakness followed by harassment by other ducks. Surviving birds showed no pattern of weight loss or gain associated with the U treatment. Necropsy revealed that the birds were in fair to excellent health and kidney and liver weights were within normal range.

10.

Wild black ducks trapped in Connecticut in 1980 were placed on a diet of natural foods and dosed via a plastic tube to the gizzard with zero, two, or five No. 6 Pb shot, or five shots administered one at a time over 2 weeks (Chasko et al., 1984). Weight loss and mortality generally increased with higher dosage. One of four birds in the two-shot group, two of four in the five-shot group, and two of five in the five-shot repeated dose group died within the 35 days of the experiment. No mortality occurred amongst controls. Mean group wing bone Pb concentrations increased from 8.5 g/g wet weight for controls to 63.8 g/g for the five-shot repeated dose group. Means for deceased ducks ranged from 75.4 g/g (five-shot group) to 104.7 g/g (five-shot repeated dose group). Mean liver Pb concentrations increased from 0.1 g/g in controls to 18.0 g/g in the five-shot repeated dose group. Group means for those that died ranged from 20.9 g/g (two-shot group) to 36.0 g/g (five-shot repeated dose group). Lead retention time varied among individual birds, with all birds eliminating shot within 21 days of final dosage. Mortality was directly related to length of Pb retention.

11.

In 1985, 10 adult black ducks were dosed with one No. 4 Pb shot and bled five times over the course of 33 days to assess the affect of Pb on hematology (Pain and Rattner, 1988). Mortality occurred in 60% of the ducks, with all 6 exhibiting signs of acute Pb poisoning (green watery feces, muscular paralysis, and lethargy) by day 3 and death occurring between days 4-6. The four surviving birds exhibited some or all of these symptoms, and all birds had pale viscera, heart, lungs, and bone marrow, and bile-stained livers. Blood Pb levels increased from 2 g/dl at day 0 to 1214 g/dl within 24 hours, and hematocrit and hemoglobin concentrations were significantly lower than controls by day 6. In surviving birds, hematocrit and hemoglobin returned to initial levels by one month. Levels of zinc protoporphyrin (ZPP) were significantly higher than control birds and ALAD activities were inhibited by 100% by day 1 and remained significantly lower than controls throughout the experiment.

12.

In the winter of 1986, one group pen-reared and one group of captive wild black ducks were dosed with one No. 4 Pb shot and redosed with either two or four additional shot after 14 days (Rattner et al., 1989). In the first 14 days, no mortality occurred, but signs of intoxication, including lethargy, muscular paralysis, and green watery feces, were observed in a portion of the ducks in each group. Hematocrit was not affected, but ALAD activity was depressed and erythrocyte protoporphyrin (EPP) concentration was elevated. After redosing, ducks showed more severe signs of intoxication, particularly wild ducks, and 40% of wild ducks succumbed after 49 days, compared to 5% of pen-reared ducks. A summer trial of this experiment in 1987 with pen-reared ducks showed less severe signs of intoxication than observed in the winter trial. Compared to results of this experiment performed with mallard ducks, both species were found to be equally tolerant to Pb shot.

13.

In 1985-86, 229 blood samples of black ducks from the Chesapeake Bay were collected for hematological analysis in relation to Pb exposure (Pain, 1989). No significant differences were found between age or sex classes, but seasonal differences in were measured between zinc protoporphyrin (ZPP) and hematocrit concentrations, and ALAD activities. At the two main sites sampled (207 ducks), the incidence of ducks with blood concentrations >40 g/dl was 14.3% in fall and 15.2% in spring. Twenty-five percent of all birds sampled had levels >30 g/dl. Hemoglobin and ZPP concentrations and ALAD ratios were found to be significantly correlated to blood lead level while no relationship existed with hematocrit. The ALAD ratio method was determined to be the most efficient field method for Pb poisoning screening.

14.

Thirty-five pen-reared adult black ducks were placed on a diet supplemented with Al sulfate (with Al levels of 200 (control), 1000, and 5000 ppm) and phosphoric acid (Ca:P ratio of 6500:21,500 ppm dry mass) to study conditions of food aversion (Sparling, 1990b). Ducks preferred the 1000 ppm Al diet over either of the two extremes, though prior experience with a high Al diet increased preference for the control diet. No effects in body weight were observed in birds consuming the 1000 ppm diet, though birds on the high Al diet experienced a drop in body weight and food consumption, suggesting that aversion may be a conditioned response to mild malaise.

IV.

Petroleum

1.

During World War II, incidence of oil exposure in wildlife was investigated along the east coast to measure the effect of increased naval activity (Peterson, 1942). Black ducks were reported to be among the hundreds of birds killed at the Brigantine National Wildlife Refuge in New Jersey when oil entered parts of Barnegat Bay.

2.

Black ducks dosed with 1 and 2 ml/kg cutting oil experienced significant inhibition of cholinesterase activity (1.80 and 0.92 mg AChE hydrolyzed per ml blood plasma per hour, respectively) as compared with controls (7.22 mg/ml) (Hartung and Hunt, 1966).

3.

Metabolic rate, or rate of heat loss, of black ducks externally exposed to lubricating oil was found to increase with decreasing ambient temperatures and increasing doses of oil (Hartung, 1967). Ducks oiled at a level of 20 g were exposed to temperatures of -26 C and all died within 6 hours. Controls did not experience any mortality. Autopsy revealed that fat reserves for both treated and control ducks had been to be depleted within the study period.

V.

Acidification

1.

Data collected between 1980-1987 from 212 lakes in central Ontario were used to determine the relationship between the presence of several species of waterfowl and the characteristics of lake area, fish presence, pH, dissolved organic carbon (DOC), and total phosphorus concentration (TP) (Blancher et al., 1992). Lakes on which black duck pairs were found had significantly higher DOC and TP values, though no correlation was found with lake area, fish presence, or pH. Black duck broods did not show a significant relationship with any of these factors though when subjected to logistic regression analysis were found to have a greater affinity for lakes without fish or a higher pH. Under the same analysis, pairs were shown to have a higher affinity for lakes with greater area, high DOC or high TP.

2.

In 1983 and 1984 a brood of human-imprinted black ducks was reared on two sets of fishless acidic (pH = 4.5 and 4.8) and fish-bearing circumneutral (pH = 6.3 and 6.5) headwater ponds in Maine (Hunter et al., 1986). The acidic ponds had greater biomass and number of invertebrates than circumneutral ponds, and invertebrate faunal structure was different between pond types. Ducklings on acidic ponds showed greater rates of weight gain and tarsi growth than on circumneutral ponds, while spending less time moving and searching and more time feeding and resting. Acidic ponds also produced a lower mean swimming velocity suggesting that abundant food supplies allowed for area-restricted foraging.

3.

Man-made, fishless acidic (pH = 5.0) and circumneutral (pH = 6.8) emergent wetlands were created as habitat for pen-reared black duck broods in order to study the effects of wetland acidification on growth and physiological condition in 1984 (Rattner et al, 1987). The acidified wetlands suffered depression in phytoplankton and algal growth and had less invertebrate biomass. Ducklings reared on the acidic wetlands had a significantly lower weight and lower culmen and tarsus lengths. These ducks also tended to have lower hematocrit, lower plasma protein, glucose, and cholesterol concentrations, and higher uric acid levels. Plasma growth hormone concentration was elevated and triiodothyronine levels were lower. The circumneutral group contained the only mortality, presumably as a result of starvation.

4.

In 1984 and 1985, a brood of human-imprinted black ducks was reared on two acid lakes and one circumneutral (pH = 6.0) control lake containing brook trout to study the effects of lake acidification and fish competition on the growth and feeding of young ducks in Quebec (DesGranges and Rodrigue, 1986). Of the two acid lakes, Lac au Cochon (pH=4.8) was fishless in 1984 and Lac du Rocher (pH=5.0) contained a healthy population of brook trout. In 1985, lac au Cochon was stocked with approximately 1500 trout while nearly 750 trout were removed from Lac du Rocher. Ducks feeding on the acid lakes moved along the shoreline at a greater rate than the circumneutral lake. In addition, in the well-stocked lakes movement was 21% faster and resting time was reduced from 16% to 13% when compared to fishless lakes. Growth rates were greatly effected on the well-stocked acid lakes where growth was 60% slower than the fishless lakes. The greatest growth rates occurred on the circumneutral lake, which contained trout, and on Lac au Cochon in 1984 when the lake was fishless. Both rates were similar.

5.

Man-made, fishless acidic (pH = 5.0) and control (pH = 6.8) emergent wetlands were created as habitat for pen-reared black duck broods in order to study the effects of wetland acidification in 1984-85 (Haramis and Chu, 1987). Half of the 36 ducklings on the acidic wetlands died, compared to 14% mortality in the control group, and only 6% gained more than five percent of their original body weight compared to 64% of the control group. Ducklings on the acidic wetland spent more time in non-foraging activities (walking, walking the fence, swimming, alert) than controls, and when foraging did take place less time was spent in aquatic habitats than controls. It was concluded that ducklings on the treated habitat probably became distressed from food deprivation and as a result spent more time on these other activities and less time foraging in normally cohesive broods.

6.

Between 1984-1986, 49 imprinted black duck ducklings were placed on three lakes, similar in most conditions except acidity and productivity, located in an area northeast of Quebec City in which acid pollutant deposition was about 22.3 pounds per acre per year (DesGranges and Hunter, 1987). Results were combined with those of Hunter et al. (1986) and Haramis and Chu (1987) to assess which factors carried the main importance in duckling starvation and growth. Biological productivity was determined to be the most important factor in that the most productive lakes studied, regardless of acidity and presence of fish, produced the least number of moribund ducklings and exhibited acceptable growth rates for duckling survival.

7.

Between 1984-1986, black ducks were reared on two Quebec lakes in which acidity, productivity, and brook trout populations were manipulated in order to assess duckling response (DesGranges and Gagnon, 1994). Black ducks were shown to change feeding habitats based on the lake acidity levels, production levels, and the presence or absence of fish. In acidic lakes containing fish, ducklings spent a greater amount of foraging time in emergent vegetation beds. In the absence of fish, ducklings changed to typical trout feeding areas including the waters surface and submerged vegetation beds. The ducks fed primarily on gnats (adult diptera), especially when fish were present, but were seen to eat substantially more benthic invertebrates after their numbers increased when lakes were treated with lime or phosphoric acid, despite the presence of fish.

8.

Four species of insectivorous ducklings, including the black duck, were collected between 1984-1986 and examined for dietary differences between individuals found on acidic (pH 5.5) and control (pH > 5.5) lakes in northeastern Ontario (Bendell and McNicol, 1995). In general, diets of the ducklings varied with lake acidity and fish presence. Specifically, black ducks saw a four-fold increase in the amount of recently emerged teneral Odonata consumed on acidic lakes and a decrease in consumption of Spongillidae and Ephemeroptera. Black ducks were the only species studied not to show an increase in the number of Anisoptera ingested on acidic lakes.

9.

One-day old black ducks were placed on diets containing various levels of calcium, phosphorus, and aluminum to mimic conditions that may be produced as a result of increased mobilization of elements due to acid rain (Sparling, 1990a). Treatments consisted of low Ca (3600 mg/kg), low P (6200 mg/kg) (LL); normal Ca (15,100 mg/kg), normal P (13,500 mg/kg) (NN); and low Ca, high P (21,500 mg/kg) (LH). Each regimen was further divided into three Al levels (200, 1000, 5000 mg/kg), and a tenth group fed normal Ca, normal P, and 10,000 mg/kg Al served as a control for Al. Birds fed the NN diet tended to gain weight more rapidly than other regimens, with growth within each regimen inversely related to Al concentration. Growth rates of tarsi, culmens, and wings also varied with diet and each parameter saw an effect to Al in at least one regimen. Surviving ducks appeared to adapt to adverse diets as differences in growth between regimens decreased with increasing length of the study. Mortality occurred among 46% of ducks, with dependency on both Ca:P regimen and Al concentration.

10.

From 1991-92, fifty-five adult black ducks were placed on one of four diets supplemented with varying cadmium and calcium levels to mimic the effects of lake acidification (Silver and Nudds, 1995). The four diets were as follows: Diet 1, 2% Ca/background Cd (control); Diet 2, 2% Ca/4 ppm Cd; Diet 3, 0.2% Ca/background Cd; Diet 4, 4 ppm Cd, 0.2% Ca. Food intake and body mass change was not significantly different among diets. Cadmium accumulation in kidneys and liver differed significantly between groups, with low Ca levels appearing to facilitate Cd uptake in these organs. Cadmium in breast tissue and fecal matter was low and similar for all groups, and no fatalities occurred as a result of Cd uptake. Birds on elevated Cd diets were significantly more active than control birds.

References for Black Duck

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Bendell, B.E. and D.K. McNicol. 1995. The diet of insectivorous ducklings and the acidification of small Ontario lakes. Can. J. Zool. 73:2044-2051.

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Cathaimer, D.F. and J.A. Dubovsky. 1997. Waterfowl: Population Status, 1997. Unpublished report. United States Fish and Wildlife Service, Office of Migratory Bird Management. 47 pp.

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Calle, P.P., D.F. Kowalczyk, F.J. Dein, and F.E. Hartman. 1982. Effect of hunters switch from lead to steel shot on potential for oral lead poisoning in ducks. JAVMA 18:1299-1301.

Chasko, G.G., Hoehn, T.R., and P. Howell-Heller. 1984. Toxicity of lead shot to wild black ducks and mallards fed natural foods. Bull. Environ. Contam. Toxicol. 32:417-428.

Clapp, R.B., D. Morgan-Jacobs, and R.C. Banks. 1982. Marine birds of the southeastern United States and Gulf of Mexico. Part II: Anseriformes. U.S. Fish and Wildlife Service, Office of Biological Services, Washington, D.C. FWS/OBS-82/20. 492 pp.

Daury, R.W., F.E. Schwab, and M.C. Bateman. 1993. Blood level concentrations of waterfowl from unhunted and heavily hunted marshes of Nova Scotia and Prince Edward Island, Canada. J. Wildl. Dis. 29:577-581.

Daury, R.W., F.E. Schwab, and M.C. Bateman. 1994. Prevalence of ingested lead shot in American black duck, Anas rubripes, and ring-necked duck, Aythya collaris, gizzards from Nova Scotia and Prince Edward Island. Can. Field-Nat. 108:26-30.

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