USGS



BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

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Biological Characteristics

Species Cygnus olor is 147-152 cm in length. Males tend to have a greater average mass (11.8 kg) than females (9.7 kg) (Dunning, 1993). This white bird has an orange bill that has a protuberance at its base (Bull and Farrand, 1977).
Status in Estuaries Breeder. This species prefers to nest in ponds, lakes, and marshes. Mute swans are highly territorial and are typically solitary nesters. Typical clutch size is 4-8 eggs (Ehrlich et al., 1988). Young are precocial (Ehrlich et al., 1988).
Abundance and Range This introduced species has established itself on the eastern seaboard of North America, between southern Maryland and coastal Massachusetts. A total of 10,268 birds were counted on the Atlantic Flyway in 1996 (Allin, 1996).
Site Fidelity Typically, once a pair has established a territory, they will return to it for many years. Some individuals remain on the territory throughout the year (Wilmore, 1979).
Ease of Census Moderate
Feeding Habits Generalist. The mute swan forages by immersing its head and bill beneath the water and searching through the sediment and by consuming aquatic vegetation, terrestrial seeds, and grasses on the water’s edge and shore. Occasionally it will eat amphibians, fish, mollusks, insects, and bread (Cramp, 1977). Young feed mostly on aquatic invertebrates for the first month of life (Ehrlich et al., 1988).


Mute Swan Contaminant Exposure Data

I.

Organochlorine Contaminants

1.

Mute swan eggs were collected from two localities in Denmark in June 1970 (Bloch and Kraul, 1972). Ten eggs collected from Suder had mean (range) concentrations of 0.333 (0.159-1.200) g/g fat weight DDE, 0.151 (0.0-0.665) g/g DDT, and 1.02 (0.69-2.29) g/g PCB. There was no DDT detected in ten eggs at the second site, Nakskov Indrefjord, but DDE and PCB were detected at concentrations of 0.335 (0.119-0.620) g/g and 3.34 (1.53-7.05) g/g, respectively.

2.

Twenty-five mute swans collected between 1980 and 1984 in Scotland contained hepatic DDE concentrations ranging from 0.01-0.1 g/g dry weight (MacDonald et al., 1987). Dieldrin, aldrin, and lindane were not detected.

3.

One egg and one embryo were collected from mute swan nests in 1997 from the Danube Delta, Romania (Aurigi et al., 2000).  Concentrations (ng/g dry weight) in egg yolk and embryo, respectively, were 170.18 and 148.01 DDT (p,p-DDT + p,p-DDE), 2.96 and 1.36 HCB, and 46.53 and 36.04 PCBPCB-77 and 169 were not detected in either the yolk or embryo, and PCB-126 was detected in the embryo only, at a concentration of 5.64 pg/g. 

4.

Eggs were collected from wild mute swans on the Chesapeake Bay in spring of 1995, and incubated (Beyer et al., 2000a).  Nine of the captive 5 month-old swans were fed sediment (24% by dry weight) from the Anacostia River, District of Columbia, mixed with waterfowl feed, and eight, were given waterfowl feed only. After 6 weeks on the diet, liver samples were analyzed for 22 organochlorines.  None of the 22 organochlorines were detected in the swan livers. 

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

1.

Heavy metal analysis was performed on 58 mute swans found dead throughout southern Sweden from 1973-1977 (Frank and Borg, 1979). Lead concentrations in liver and kidney were <1 g/g wet weight in 23 birds, between 1-2 g/g wet weight in 15 birds, between 2-5 g/g in 9 birds, and >5 g/g in 10 birds. In general, kidney values were slightly higher than liver values, and the average concentration about three times greater in the >5 g/g swans. Cadmium levels ranged from 0.05-42 g/g in kidney and 0.05-11.5 g/g in liver, and a significant difference was found between the mean renal concentration of juveniles (0.9 g/g) and adults (9.1 g/g). Cadmium concentrations were significantly higher on the Swedish east coast compared to the west coast. Copper concentrations in the liver ranged from 37-3820 g/g and were >1000 g/g in about 30% of the swans. Levels of Cu in the kidney ranged from 1.2-51 g/g. In 41 swans, Fe concentrations ranged from 195-5620 g/g in liver and 79-470 g/g in kidney, and Mn values ranged from 1.2-5.9 g/g in liver and 0.6-5.0 g/g in kidney.

2.

In 1976-77, mute swans, many of which had died of Pb poisoning, were collected from Denmark for Cu and Pb analysis: 32 from lagoons near lsemagle, an industrial area; 15 from Rdby, with little or no industry; and 44 from various sites around the country (Clausen and Wolstrup, 1978). In the liver, mean (range) Cu concentrations were 1096 (220-2740) g/g wet weight at lsemagle, 391 (125-875) g/g at Rdby, and 418 (52-1500) g/g in other areas. In lsemagle, 13 swans had Cu concentrations >1000 g/g in the liver. Mean Cu values in the kidney were 48 (13-450) g/g at lsemagle, 11 (6-15) g/g at Rdby, and 16 (6-35) g/g in other areas. Differences in Cu concentration between sex and age groups were not detected. Lead, analyzed only in the liver, averaged 36 (1-103) g/g at lsemagle, 40 (2-100) g/g at Rdby, and 8 (1-61) g/g in other areas.

3.

Of 20,000 mute swans that died during the severe winter of 1978-79 in Denmark, 178 were analyzed for heavy metals (Elvestad et al., 1982). Kidneys of 110 swans that were analyzed for Cu and Cd had mean levels of 34 and 23 g/g dry weight, respectively. Utilizing all 178 liver samples, mean metal concentrations were 2680 g/g Cu, 12 g/g Cd, and 15 g/g Pb. Mercury was measured in ten livers, at a mean of 1.4 g/g. Lead was determined in the sternum of 110 swans at a mean concentration of 31 g/g.

4.

Signs of Pb poisoning were examined in 2111 of the 20,000 swans that died in Denmark during the winter of 1978-79 (Clausen et al., 1982). Forty-seven, or 2%, of the birds showed signs of Pb poisoning. In 30 of these cases, poisoning was confirmed by Pb concentrations in tissue, or presence of Pb pellets in the gizzard. Following autopsy, 76 of the swans were analyzed further and 15 contained Pb pellets in the gizzard. Of those 15 swans, 10 showed signs of Pb poisoning at autopsy. The mean concentration of Pb in the liver was calculated as 6 g/g wet weight for the 76 swans autopsied and 4 g/g for 184 banded swans. Sternal bone from 110 banded swans was found to contain a mean Pb concentration of 31 g/g dry weight. In 68 swans, a positive correlation was found between age and Pb load in the bone, but no correlation was found with liver burden.

5.

Of 94 mute swan collected in 1979 from the River Thames, 54 were determined to have died from Pb poisoning due to ingestion of Pb fishing sinkers (Birkhead, 1982). Median (range) Pb concentrations in these birds were 105 (10-562) g/g dry weight in liver and 908 (105-5225) g/g in kidney, and the number of Pb weights found in the gizzard ranged from 0-28. In birds dying from other causes, Pb concentrations were 4 (1-22) g/g in liver and 8 (1-116) g/g in kidney, and no Pb shot was found in the gizzard. Lead tissue concentrations were also determined in a healthy and in a Pb-poisoned mute swan taken for ultrastructure examination. The healthy bird had a Pb concentration of 57 g/g 100 mls in blood, 4 g/g dry weight in liver, 8 g/g in kidney, and no shot in the gizzard. The Pb-poisoned swan contained 354 g/g 100 mls in blood, 120 g/g in liver, 1085 g/g in kidney, and 5 shot in the gizzard.

6.

Examination of Pb pellets and tissue concentrations was conducted on mute swans found dead in 23 sample areas in England between 1979-81 (Mudge, 1983). Of 32 swans examined, 7 contained ingested pellets in the gizzard (1 contained a single pellet, 1 contained two pellets, 3 contained four pellets, and 2 contained six or more pellets). Livers of six of these birds were analyzed and contained Pb concentrations ranging from 11.6-32.7 g/g dry weight, with a mean of 19.0 g/g. Livers of 22 swans that did not contain shot in their gizzard were also analyzed, and Pb values ranged from 0.5-12.7 g/g, with a mean of 2.9 g/g.

7.

Blood Pb concentrations were determined in mute swans on the Thames River as part of a breeding biology study between 1979-82 (Birkhead and Perrins, 1985). Median blood Pb concentrations in incubating females in 1980 and 1981 were 120 and 92 g/dl on the Upper Thames, 113 and 59 g/ 100 ml on the Lower Thames, and 39 and 33 g/dl on the tributaries. Cygnet blood concentrations on the Lower Thames were 32 g/dl in 1980 and 102 g/dl in 1981, and in the Oxford study area 15 g/dl in both years. Over 50% of cygnets had levels >40 g/dl. In general, Pb concentrations increased with proximity to London.

8.

Blood samples were collected for Pb analysis from mute swans on the River Thames and three of its tributaries in 1980 and 1981, and from a control site in Dorset in 1979 (Birkhead, 1983). Of 99 swans sampled in Doreset, all had blood Pb levels below 33 g/dl, with a median of 9 g/dl. Using these data, combined with that of previous studies, a maximum acceptable level of 40 g/dl was determined. In general, very few swans on the Thames had Pb concentrations below this level. Analysis from the Thames showed that levels of Pb increased significantly with proximity to London, and in 1981, only birds from the tributaries had concentrations below 40 g/dl. Seasonal variation was observed as highest lead levels were recorded in July, August, and September, during the coarse fishing season, and lowest were recorded in April, when means dropped below 40 g/dl. During the breeding season, females had significantly higher levels than males: 35 g/dl compared to 15 g/dl on the tributaries, and 100 g/dl compared to 30-40 g/dl on the Thames. Cygnets sampled in 1980 and 1981 on the Thames contained median levels (37 and 92 g/dl, respectively) significantly higher than those sampled on the tributaries (10 and 12 g/dl).

9.

Blood Pb concentrations were determined by age-class in 132 mute swans sampled from several locations in Ireland (OHalloran and Duggan, 1984). Concentrations ranged from 4.14-354 g/dl in adults, 4.14-1477.0 g/dl in sub-adults, and from 5.2-29.80 g/dl in cygnets. Three swans had concentrations >1400 g/dl. One adult diagnosed with Pb poisoning contained tissue Pb concentrations of 652 g/dl in blood, 4.24 g/g wet weight in breast muscle, 57.34 g/g in the heart, 111.78 g/g in kidney, 44.43 g/g in liver, 43.78 g/g in the pancreas, and 4 Pb shot in the gizzard. A cygnet that died from a collision with a cable wire contained 18.6 g/dl Pb in blood, 1.86 g/g in heart, 2.4 g/g in kidney, 5.11 g/g in liver, and no shot in the gizzard.

10.

Of 70 mute swans collected between 1980 and 1984 in Scotland, 6 contained Pb concentrations in the liver >125 g/g dry weight and were diagnosed with Pb poisoning (MacDonald et al., 1987). Forty swans had concentrations between 1-10 g/g, 17 were between 11-44 g/g, 4 were between 45-124 g/g, and concentrations in the remaining 3 were not determined. Kidney Pb concentrations of four birds which did not die from poisoning ranged between 1.0-5.0 g/g. Concentrations of Hg were determined in 25 swans and ranged between 0.02-1.4 g/g liver wet weight.

11.

Mute swans in Scotland were analyzed for Pb in the blood, tissues, and gizzards between 1980 and 1986 (Spray and Milne, 1988). Fourteen swans that had succumbed to Pb poisoning had median (range) Pb levels of 90.6 (14-410) g/g dry weight in the liver and 364 (57-3340) g/g in the kidney. Five of these birds contained Pb shot in the gizzard (number of shot ranging from 1-944) and three contained anglers weights. Sixty-seven birds found dead from other causes had levels of 2.8 (0.2-16.5) g/g in the liver and 3.1 (0.2-35) g/g in the kidney, and no Pb was detected in the gizzard. Of 65 birds found dead in which bone Pb was measured, 47 contained concentrations of 0-9 g/g, 17 between 10-19 g/g, and 1 between 20-29 g/g. From 1983-86, 544 blood samples were taken throughout Scotland, and Pb levels ranged from 7-1370 g/dl, with a median of 52 g/dl.

12.

Between 1981 and 1982, 320 mute swan carcasses, 70% of which were females, were collected from approximately 300 miles of English rivers and examined for evidence of Pb ingestion (French, 1982). Lead shot was present in the alimentary tract of 174 swans. A total of 180 birds had Pb levels exceeding 125 g/g dry weight in the kidney, and 50 g/g in the liver. An additional 44 of the swans had levels ranging from 38-64 g/g in the kidney, 13-32 g/g in the liver, and 40-86 g/g in bone.

13.

During a cold winter three mute swans were found dead in Mamaroneck Harbor, New York State (Molnar, 1983). When performing a necropsy it was noted that the livers from these birds appeared to have a "coal-black" appearance. Copper was considered the most likely cause to explain the abnormalities, with an average liver concentration of 3,957 g/g dry weight. This value was greatly elevated over concentrations found in captive swans of 92.5 g/g dry weight. It is believed that the main exposure to the Cu was through antifouling paint.

14.

During molting, blood was drawn for Pb analysis from 128 mute swans captured from Ringkbing Fjord in Denmark (Eskildsen and Grandjean, 1984). Of the adults, median (range) blood Pb levels were 24 (13-54) g/dl for 61 males and 27 (13-45) g/dl for 21 females. In juveniles, medians were 12 (7-39) g/dl for 20 males and 11 (7-18) g/dl for 26 females.

15.

Of 166 mute swans examined from 1983-86 in the Thames area in England, 66 were determined to have died from Pb poisoning (Sears, 1988). Of the Pb-poisoned swans, 51 contained Pb pellets in the gizzard, with a mean of 5.8 pieces of Pb per bird, and a maximum of 30 pieces in one bird. Blood lead levels were determined for 502 swans from seven flocks from 1982-85, and varied regionally from a median (range) of 32 (2-230) g/dl in the Upper Thames and its tributaries to a median of 166 (46-1935) g/dl in the Richmond area.

16.

From December 1984 to November 1986, 823 blood samples were collected for lead analysis from 456 banded mute swans which were caged for 15 hours and released (OHalloran et al., 1988a). Hematocrit, hemoglobin, and blood Pb levels varied among and between birds both night and day for samples drawn while birds were caged and while in the wild. Blood Pb levels, corrected for hemoglobin, which varied the least, ranged from 0.46 to 106.30 g Pb/g hemoglobin. Lead concentrations were found to vary seasonally, with higher values occurring in the winter and spring. Blood Pb levels also varied with molting, as concentrations were lower during the molting period. There was no difference in Pb concentrations between sexes or age classes.

17.

From December 1984 to November 1986, mute swan blood samples were collected for Pb analysis from 6 sites in Ireland (OHalloran et al., 1988c). In urban areas, 17% of swans had elevated blood Pb levels (>3 g Pb/g hemoglobin) compared to only 4.5% at rural locations. At urban sites, 27.5% of birds had Pb concentrations between 2-3 g Pb/g hemoglobin compared to 13.5% at rural sites. One bird found dead had a value of 62 g Pb/g hemoglobin. At Cork Lough, blood Pb concentrations ranged from 0.46-106.3 g Pb/g hemoglobin and 42% of birds had elevated levels. Of mute swans found dead, 10 with ingested anglers pellets had Pb concentrations of 40-305 g/g wet weight in kidney and 170.5-450 g/g in liver. Thirty swans with no ingested Pb had kidney concentrations of 0.4-145 g/g and liver concentrations of 1-550 g/g. Shot pellets were found in 49 swans, 5-100 per bird, and Pb kidney values ranged from 142-350 g/g in these birds. Of 41 birds radiographed, 27% had Pb in their bodies, 8 via ingestion and 3 via shot-in pellets. Blood Pb levels ranged from 1.45-2.6 g Pb/g hemoglobin in birds with shot-in Pb and from 2.5-80.73 g Pb/g hemoglobin in birds with up to 11 ingested pellets.

18.

Four mute swans suffering from Pb poisoning in Ireland were collected for hematological and tissue analysis (O'Halloran et al., 1988b). Lead concentrations were highest in the kidney (18.4-334 g/g) and liver (42-145 g/g). Levels were also determined in the pancreas (10.1-240 g/g), heart muscle (1.2-160 g/g), breast muscle (1.2-46 g/g), and gizzard muscle (5.6-28 g/g). Lead pellets were recovered from two of the birds (7 and 14 pellets per bird).

19.

Sixty-three mute swans found dead from Scotland (1985-1987) were submitted for post-mortem exam (Macdonald et al., 1990). Six of the swans examined had kidney Pb concentrations >125 g/g dry matter, indicative of Pb poisoning.

20.

Concentrations of Pb were determined in dead mute swans collected from Ireland (OHalloran et al., 1989). For those diagnosed with Pb poisoning, median concentrations were 113 g/g wet weight kidney, 315 g/g liver, 67 g/g pancreas, 14.5 g/g heart muscle, 13 g/g gizzard muscle, and 19 g/g breast muscle. Those which died from collisions, median concentrations were 28.24 g/g kidney, 33 g/g liver, 21 g/g pancreas, 12.1 g/g heart, 12.8 g/g gizzard, and 18.2 g/g breast. Those which died from other causes had Pb concentrations of 8.7 g/g kidney, 8 g/g liver, 11 g/g pancreas, 6.5 g/g heart, 6.8 g/g gizzard, and 9 g/g breast. Ingested Pb weights were found in 7 of 10 of the birds diagnosed with Pb poisoning. Blood Pb concentrations ranged from 0.46-16.55 g/g in swans with elevated Pb levels.

21.

Three swans (two adults and one cygnet) that died following a 1988 oil spill at the Milford Haven Oil Terminal, UK, contained low hepatic Pb concentrations, ranging from 6-37 ng/g (Quick, 1993). 

22.

Eight of nine mute swans released near Tottori, Japan, died within a period of 40 days in the summer of 1989 and were diagnosed with Cu poisoning (Kobatashi et al., 1992). Concentrations of Cu in the liver of seven affected swans ranged from 630-7170 g/g dry weight as compared to 120-360 g/g in controls. Other contaminants detected in the liver were Zn (80-620 g/g affected swans, 10-160 g/g controls) and Na (17800-24500 g/g affected swans, 16100-19800 g/g controls).

23.

In 1995, 42 mute swans were collected from four relatively unpolluted areas of Chesapeake Bay (Beyer et al., 1998). Metal concentrations in the liver were compared to those of the intestinal digesta. Mean and/or range values in the liver were: 18 (<5.0-140) g/g dry weight Al, <0.50-1.5 g/g Ba, 3.9 (<2.0-9.9) g/g B, 16 (2.9-94) g/g Cd, 1200 (240-3000) Cu, 5000 (1600-19,000) g/g Fe, 1.5 (<1.0-6.3) g/g Pb, 680 (520-800) g/g Mg, 12 (4.6-20) Mn, <0.50-1.0 g/g Ni, 0.56 (<0.20-3.2) g/g Sr, <0.50-1.3 g/g V, and 290 (79-770) g/g Zn. Concentrations in digesta were: 590 (11-3400) g/g Al, 6.6 (<0.76-32) g/g Ba, 76 (<2.8-760) g/g B, 1.4 (<0.15-14) g/g Cd, 20 (5.7-140) Cu, 1300 (180-6300) g/g Fe, 1.6 (<1.5-6.4) g/g Pb, 4000 (850-8300) g/g Mg, 310 (5.2-2500) Mn, 3.4 (0.74-18) g/g Ni, 57 (0.83-130) g/g Sr, 1.8 (<0.74-7.8) g/g V, and 110 (40-480) g/g Zn. The swans were estimated to have ingested 3.2% sediment in their diets. Concentrations of Pb in digesta increased with acid-insoluble ash in the feces, indicating the necessity of utilizing sediment ingestion rates when assessing exposure.

24.

Carcasses of 41 mute swans, collected between January 1995 and December 1996, were analyzed for Pb at S.A.C. Veterinary Science Division, Auchincruive, Ayr, Scotland (Pennycott, 1999).  Of 14 birds collected from a single pond where several swan mortalities had been reported, 8 had confirmed cases of Pb poisoning (>100 g/g g dry weight in kidney), with 6 of these poisoned birds containing Pb weights in their gizzard.  Four other birds from this group had renal Pb concentrations of 11-100 g/g.  Of 27 birds collected individually from various sites in central and western Scotland, only 1 had a confirmed case of Pb poisoning (Pb shot present in gizzard), and Pb poisoning was suspected in 2 others.

25.

Eggs were collected from wild mute swans on the Chesapeake Bay in spring of 1995, and incubated (Beyer et al., 2000a).  Nine of the captive 5 month-old swans were fed sediment (24% by dry weight) from the Anacostia River, District of Columbia, mixed with waterfowl feed, and eight, were given waterfowl feed only. After 6 weeks on the diet, liver samples were analyzed for Al, B, Ba, Cd, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V, and Zn.  Hepatic Pb concentrations were <1.0 in control swans and <2.0 in treatment swans.  Concentrations of most metals in the treatment swans were similar to controls, despite one to ten-fold higher levels of metals in the diet of the treatment swans.  For elements that showed differences, mean hepatic concentrations (g/g dry weight) for control and treated swans, respectively were, 0.21 and 0.44 Cd; 470 and 570 Mg; 97 and 130 Zn; and 1.2 and 1.8 Mo.

26.

Five month old swans were experimentally fed several different diets containing varying amounts of sediment from Coeur dAlene River basin for 5 to 15 weeks (Beyer et al., 2000b, data from Day et al., 1998).  On a commercial waterfowl feed diet containing no sediment, blood Pb was 0.19 mg/kg wet weight, and hepatic Pb was 0.15 mg/kg.  On a diet with 24% reference sediment from St. Joe River, Idaho, and either rice or commercial waterfowl feed, blood Pb was 0.20 mg/kg, and hepatic Pb was 0.16 mg/kg. On a diet with 12% sediment from Harrison Slough, in the Coeur dAlene River basin, Idaho, and commercial waterfowl feed, blood Pb was 1.3 mg/kg, and hepatic Pb was 1.5 mg/kg.  On a diet with 24% sediment from Harrison Slough, in the Coeur dAlene River basin, Idaho, and commercial feed or rice, blood Pb was 2.3 and 3.2 mg/kg, respectively and hepatic Pb was 3.8 and 8.5 mg/kg. 

IV.

Petroleum

1.

Mute swans were among 100 birds rescued from a 10,000-ton fuel oil spill at the Biesboch reserve and bird sanctuary, Holland, in 1970 (Van Kampen, 1971).

2.

In 1972, 200 out of 278 mute swans observed in the Cromarty Firth, Easter Ross, north-east Scotland, had evidence of oil exposure after fuel oil was discharged from two nearby distilleries (Bourne, 1975).

3.

As part of an investigation of high avian mortalities in the North Irish Sea and Firth of Clyde in 1974, 11 mute swans (7 alive and 4 dead) in Ayshire were found to be oiled (Lloyd et al., 1974).

4.

Of thirteen swans rescued following a 1988 oil spill at the Milford Haven Oil Terminal, UK, two adults and one cygnet died during rehabilitation efforts (Quick, 1993).  Residue levels of pristane in adults tissues were 0.96 and 0.47 g/g in liver, 0.32 and 0.57 g/g in kidney, and 58.4 and 87.7 g/g in feathers.  Concentrations in the cygnet were 0.33 g/g in liver, 0.55 g/g in kidney, and 324.0 g/g in feathers.  Total hydrocarbon (light crude oil) concentrations in feathers were 7.3 and 11.00 mg/g in adults and 41.00 mg/g in the cygnet.

V.

Other

1.

Radio-iodine was measured in thyroid glands of 200 mute swans that died in the East Midlands of England during 1979-83 (Howe and Hunt, 1984). Of 59 swans found dead on the River Trent, 40 contained I-125 (10-5091 mBq/g fresh weight) and 8 contained I-131 (340-5365 mBq/g). On tributaries of the River Kent, 25 of 58 swans contained I-125 and 10 contained I-131. Of swans not found on the River Trent or its tributaries, only 2 of 55 had detectable levels of radio-iodine. Radio-iodine (I-131) was not detected in dried liver samples from 7 swans (3 of which had positive thyroids) or tissues and organs of a swan with a concentration of 5091 mBq/g I-125 in the thyroid.

 Mute Swan Contaminant Response Data

I.

Organochlorine Contaminants

1.

Ten mute swan eggs collected from each of two localities in Denmark, Suder and Nakskov Indrefjord, in June 1970 had low concentrations of DDE and mean eggshell thickness values were quite similar (0.71 mm and 0.70 mm, respectively) (Bloch and Kraul, 1972).

2.

Eggs were collected from wild mute swans on the Chesapeake Bay in spring of 1995 and incubated in the lab (Beyer et al., 2000a).  Nine of the captive 5 month-old swans were fed sediment (24% by dry weight) from the Anacostia River, District of Columbia, mixed with waterfowl feed, and eight, were given waterfowl feed only. Mean body weight increased from 7.6 to 8.2 kg in the treatment and from 7.9-8.5 in the control group.  Hepatic monooxygenase activity was significantly higher in treated swans than controls (EROD: 324 and 111 pmol product/min/mg, respectively; MROD: 583 and  249 pmol product/min/mg; and BROD: 128 and 4.5 pmol product/min/mg).  The PAHs known to induce cytochrome P450 were present in the sediment used in the treatment feed. 

II.

Cholinesterase-Inhibiting Pesticides

 

No response data available

III.

Trace Elements, Metals, and Metalloids

A.

Lead Poisoning

1.

Causes of mortality were examined in 193 British mute swan deaths reported from 1951 to 1989 (Brown et al., 1992). Of 127 adults, 23% died of Pb poisoning, and of 56 juveniles, 16% died of Pb poisoning. Of 10 downies, (first-year birds that have not developed their primary feathers), there were no cases of Pb poisoning.

2.

In November 1972, an adult male mute swan was observed swallowing a fishing sinker and within eight days developed signs of Pb poisoning including listlessness, refusal to eat, a swollen head, a flaccid cere, and a vent area that was stained dark green (Gelston and Stuht, 1975). Radiographic analysis revealed five fishing sinkers and a fishing swivel in the gizzard. The bird was treated with daily injections of calcium disodium versenate for three weeks, and appeared to make a complete recovery.

3.

Fifty-eight mute swans found dead throughout southern Sweden were collected between 1973-1977 (Frank and Borg, 1979). Ten birds had Pb concentrations >5 g/g in liver and were diagnosed with Pb poisoning. Some swans with highly elevated Pb showed a greenish discoloration around the cloaca, and two such birds exhibited accumulation of foodstuffs in the esophagus and proventriculus.

4.

Mute swans found dead from Nottingham had a mean weight of 6.7 kg (Simpson et al., 1979). These values were lower than the control herd with a mean weight of 10.0 kg. Swans poisoned with Pb exhibited anorexia symptoms, their plumage was soiled (often with traces of mineral oil in the breast region), the pectoral muscles were atrophied, the liver, gizzard, and spleen were smaller than normal, although adrenal glands were heavier.

5.

Mute swans found dead in Denmark were collected for Pb analysis from the period of June 1975 to January 1977, then again in 1979 (Andersen-Harild et al., 1982). Of a total of 552 swans radiographed, 76 were found to contain Pb pellets, of which 14 were diagnosed to have died from Pb poisoning, 49 starvation, 8 injury, and 5 infection. An additional 49 swans with no signs of pellets were also diagnosed with Pb poisoning. The number of pellets in the gizzard averaged 3.6 per bird.

6.

Of 94 dead mute swan collected in 1979 from the River Thames, 54 were determined to have died from Pb poisoning due to ingestion of Pb fishing weights (Birkhead, 1982). All but one of the cases contained split shot used by anglers, an average of 7 per bird, and the remaining case contained 32 gun shot pellets in the gizzard. Birds which died of Pb poisoning were emaciated, showed impaction of the proventriculus and gizzard and a distended gall bladder, and weighed less than birds which died of other causes. Those observed prior to death showed an abnormal carriage to the neck, a vent region stained green with liquid feces, and lethargy. Birds with Pb weights in the gizzard had significantly greater median Pb concentrations (105 g/g dry weight liver, 908 g/g kidney) than those with none (4 g/g liver, 8 g/g kidney). More birds died as a result of Pb poisoning from July-October than other months. Ultrastructural analysis revealed electron dense intra-nuclear inclusions in the cells of proximal convoluted tubules of the kidney which confirmed that these structures consisted of Pb.

7.

In 1979, two mute swans were among about 2400 birds to die in the Mersey Estuary, UK, between 1979-1981 from alkyl Pb poisoning derived from petrochemical industrial effluent (Bull et al., 1983).

8.

Blood Pb concentrations were determined in mute swans on the Thames River as part of a breeding biology study between 1979-82 (Birkhead and Perrins, 1985). Hatching success was similar among incubating females even though swans on the Thames had significantly higher blood Pb concentrations than those on the tributaries. In evaluating cause of death, 10 of 14 cygnets, 30 of 35 immatures, and 6 of 8 adult swans on the Lower Thames were found to have died from Pb poisoning. In the Oxford study area, 1 of 7 cygnets, 6 of 14 immatures, and 4 of 11 adults were diagnosed with Pb poisoning.

9.

The ultrastructure of kidney, liver, blood, and intestine was compared between a Pb-poisoned and a healthy mute swan (Birkhead et al., 1982). The Pb-poisoned swans had a blood Pb concentration of 354 g/g and exhibited classic signs of Pb-poisoning. In the kidney, intra-nuclear inclusions were observed in the proximal tubules of the poisoned bird and Pb was detected via X-ray microprobe analysis. In the liver, the poisoned bird had a greater frequency and density of electron dense granules, which were found to contain Fe in large amounts. In blood, many erythrocytes of the poisoned bird had intracellular electron dense granules lying in the cytoplasm just inside the plasma membrane. In the intestine, villi in the poisoned bird appeared to be reduced in length and number, though it could not be determined if this was a result of Pb-poisoning.

10.

One adult swan found moribund in Ireland with four Pb shot in the gizzard was diagnosed with Pb poisoning (OHalloran and Duggan, 1984). The bird exhibited an abnormal carriage of the neck and remained solitary, drifting aimlessly on the water and feeding only once in four days. In post mortem examination, the carcass was noticeably light, the pectoral muscles exhibited significant atrophy, the liver was unusually dark, the gall-bladder distended, the heart flaccid, and the esophagus, proventriculus, and gizzard were impacted with food. The epithelium of the gizzard was yellow in color and broken away form the basement membrane.

11.

Of 70 mute swans collected between 1980 and 1984 in Scotland, 6 contained Pb concentrations in the liver >125 g/g dry weight and were diagnosed with Pb poisoning (MacDonald et al., 1987). In four of these birds, the digestive tract was impacted with course fibrous material such as long grass. Three birds with kidney Pb concentrations of 45-124 g/g were determined to have died from adverse environmental conditions.

12.

Of 149 mute swans found dead in Scotland between 1980 and 1986, 13% were diagnosed with Pb poisoning (Spray and Milne, 1988). Deaths occurred throughout the year, with the highest number occurring from January to April.

13.

Of 600 mute swans collected from Great Britain, 468 (78%) had died of Pb poisoning (French, 1984). There was no difference in the percent of birds diagnosed with Pb poisoning when the fishing season was opened or closed.

14.

Between 1981 and 1982, 224 of 320 mute swan carcasses collected from approximately 300 miles of English rivers were determined to have died from Pb poisoning (French, 1982). Eight moribund swans showed symptoms of anorexia, weakness, inability to move correctly, impaction of the esophagus, emaciation, and a drop in body temperature up to 72 hours before death. All 174 birds containing Pb shot were diagnosed with Pb poisoning, and 180 birds had Pb levels in the kidney and liver in excess of that which would confirm fatal poisoning in mammals. Forty-four birds had moderate levels of Pb in their tissues but were diagnosed with Pb poisoning due to post-mortem signs including esophageal, proventricular, and gizzard impaction, wasting of muscle, high levels of iron in the liver, an enlarged gall bladder, and presence of Pb fishing weights in the gizzard. During the period of collection, the East Anglian region experienced temperature of -17C, which is hypothesized to have contributed to the weakening of the swans.

15.

Of 166 mute swans examined from 1983-86 in the Thames area in England, 66 were determined to have died from Pb poisoning (Sears, 1988). Of the Pb-poisoned swans, 51 contained Pb pellets in the gizzard. The percent of birds diagnosed with Pb poisoning varied regionally from 16.7% in the Upper Thames and its tributaries to 93.5% in the Richmond area. Blood Pb levels followed a similar regional pattern.

16.

Lead poisoning was the largest cause of illness, accounting for 317 of 518 cases, in mute swans collected on the River Thames between 1983-86 (Sears et al., 1989). Of these swans, 174 had ingested anglers weights in the gizzard totally 966 weights in all swans. A chelation therapy, using sodium calcium edetate, resolved the clinical signs of Pb poisoning in 49% of the cases. At least 22% of treated swans survived the first two years, and results indicated that once a swan becomes poisoned, despite treatment, its chances of survival are reduced by 59% compared with untreated swans living in flocks. Eleven of 155 swans treated for Pb poisoning bred within three years of release.

17.

In 1985, mute swans were collected from two sites near Reading, England (Pain, 1987). In swans with blood Pb concentrations between 5-100 g/dl, Pb values were found to correlate negatively with ALAD activity. Swans with Pb values >100 g/dl exhibited a high degree of reticulocytosis. Reticulocytes accounted for 50-90% of erythrocytes, compared to about 2% in unexposed birds. In swans defined as "heavily lead contaminated", 50% showed a marked degree of poikilocytosis ("tear drop" cells) in blood. No relationship was found between hematocrit levels and blood Pb concentration.

18.

From December 1984 to November 1986, 823 blood samples were collected for blood Pb and protoporphyrin analysis from 456 uniquely ringed mute swans that were caged for 15 hours and released (OHalloran et al., 1988a). Protoporphyrin values ranged from 1.90 g/g hemoglobin in normal healthy birds to 40 g/g hemoglobin in acutely Pb poisoned birds. Protoporphyrin did not vary with time of day in samples collected from caged birds or in the wild. The use of free red blood cell protoporphyrin as a method for detecting Pb exposure was assessed via comparison to whole blood lead levels. Using blood lead levels, 44% of 357 samples were determined to have elevated Pb levels, while 34.5% were determined as elevated for the same sample using free red blood cell protoporphyrin.

19.

From December 1984 to November 1986, 101 dead or moribund mute swans were collected for Pb analysis in Ireland (OHalloran et al., 1988c). Ten swans with ingested anglers pellets had kidney and liver concentrations diagnostic of acute Pb poisoning. Ten swans had no pellets, but also had kidney and liver concentrations and pathological findings indicating Pb poisoning. Forty-nine swans had shotgun pellets in the gizzard, and tissue concentrations also exceeded those indicative of Pb poisoning. Based on diagnostic tissue Pb levels, 68% of all swans examined were determined to have died from Pb poisoning. Pathological signs included gross emaciation, impaction of the gizzard and esophagus, and distended gallbladder. Most Pb-poisoned birds died in the winter months.

20.

In addition to 374 healthy mute swans, 4 swans suffering from Pb poisoning in Ireland were sampled for biochemical and hematological parameters (OHalloran et al., 1988b). Increased values of protoporphyrin IX, cholesterol, lactate dehydrogenase, and aspartate aminotransferase were found in the poisoned swans as compared with levels in the healthy swans. Concentrations of hemoglobin and mean cell hemoglobin concentration indicated hypochromic anemia.

21.

Dead mute swans collected from Ireland were analyzed for sublethal effects of Pb exposure (OHalloran et al., 1989). Swans with Pb concentrations in the muscle (heart, breast, and gizzard) between 6-270 g/g were diagnosed with Pb poisoning. Birds that had died from collisions had high Pb concentrations in the liver, kidney, and particularly the breast muscle. Swans with high Pb concentrations had lower hemoglobin concentrations. Hematological changes and changes in blood Pb levels are examined in three swans involved in collisions and those with elevated Pb concentrations.

22.

Eggs were collected from wild mute swans on the Chesapeake Bay in spring of 1995, and incubated (Beyer et al., 2000a).  Nine of the captive 5 month-old swans were fed sediment (24% by dry weight) from the Anacostia River, District of Columbia, mixed with waterfowl feed, and eight, were given waterfowl feed only. Mean hematocrit, hemoglobin concentrations, and protoporphyrin concentrations were similar in treated and control swans.  Red blood cell ALAD was significantly depressed in treated swans (25 units) compared to controls (174 units), though the mean hepatic Pb concentration in treated birds was <2.0g/g dry weight.

23.

Five months old swans were experimentally fed several different diets containing varying amounts of sediment from Coeur dAlene River basin, Idaho, for 5 to 15 weeks (Beyer et al., 2000b, data from Day et al., 1998).  On a commercial waterfowl feed diet containing no sediment: blood Pb was 0.19 mg/kg wet weight, red blood cell ALAD activity was 174 units, protoporphyrin was 85 g/dl, hemoglobin was 17.0 g/dl, and hepatic Pb was 0.15 mg/kg.  On a diet with 24% reference sediment from St. Joe River, Idaho, and either rice or commercial waterfowl feed, respectively, blood Pb was 0.20 and 0.20 mg/kg, ALAD activity was 125 and 139 units, protoporphyrin was 96 and 92 g/dl, hemoglobin was18.3 and 17.0 g/dl, and hepatic Pb was 0.16 and 0.16 mg/kg. On a diet with 12% sediment from Harrison Slough, in the Coeur dAlene River basin, and commercial waterfowl feed, blood Pb was1.3 mg/kg, ALAD activity was 3.9 units, protoporphyrin was 306 g/dl, hemoglobin was 16.0 g/dl, and hepatic Pb was1.5 mg/kg.  On a diet with 24% sediment from Harrison Slough, in the Coeur dAlene River basin, and commercial feed or rice, blood Pb was 2.3 and 3.2 mg/kg, ALAD activity was 8.8 and 4.4 units, protoporphyrin was 530 and 465 g/dl, hemoglobin was13.4 and 13.6 g/dl, and hepatic Pb was 3.8 and 8.5 mg/kg.  Renal inclusion bodies were found only in birds with 24% sediment in diets, in all birds on both diets.

B.

Reproductive Effects

1.

Blood Pb concentrations were determined in mute swans on the Thames River as part of a breeding biology study between 1979-82 (Birkhead and Perrins, 1985). Hatching success was similar among incubating females even though swans on the Thames had significantly higher blood Pb concentrations than those on the tributaries.

2.

In 1980-81, six incubating mute swans on the River Thames with blood Pb levels >200 g/dl showed poor reproductive success and low chances of survival (Birkhead, 1983). Those with levels of 436 and 820 g/dl failed to produce any eggs that hatched. Those with levels of 230, 271, and 293 g/dl had hatching rates of approximately 50-75%, but all offspring died in the first week. One female with a concentration of 217 g/dl had 63% hatching success, and all young fledged. Only two of the females were known to have survived to breed the following year. Lead levels in surviving cygnets were not observed to correlate with survival rates.

C.

Other Metals

1.

Fifty-eight mute swans found dead throughout southern Sweden were collected between 1973-1977 (Frank and Borg, 1979). Cadmium concentrations reached 42 g/g wet weight, yet no lesions were found on the kidney or any other organ to indicate harmful effects. One swan, which had ingested a metallic Cu piece attached to a fishing hook and showed general signs of anemia, had highly elevated Cu levels as compared with other samples, 3820 g/g liver and 51 g/g kidney, and was diagnosed with Cu poisoning.

2.

Eight of nine mute swans released near Tottori, Japan, died within a period of 40 days in the summer of 1989 and were diagnosed with Cu poisoning (Kobatashi et al., 1992). In seven swans pathologically examined, all contained yellowish-brown to greenish-brown granules in the cytoplasm of hepatocytes that were intensely stained with rhodanine Cu stain, schmorl method and Berlin blue stain. Many lysosomes increased in size and density in the cytoplasm of hepatocytes. Evidence of Cu, Zn, and Na was found in the liver, though Cu concentration was found to be significantly higher than that of a control group.

IV.

Petroleum

1.

Of thirteen swans rescued following a 1988 oil spill at the Milford Haven Oil Terminal, UK, two adults and one cygnet died during rehabilitation efforts (Quick, 1993).  The adults swans were totally devoid of body fat and weighed only 8.25 and 8.1 kg, compared to the cygnet which weighed 6.25 kg and had retained adequate reserves of fat.  Gizzards contained little but sand and fine grit, livers were a very dark color, and the gall bladders were full.

V.

Other

1.

Mute swans were collected as eggs from Chesapeake Bay in 1995, raised in pens, and dosed with 0-5.28 mg white phosphorous (P4) / kg body weight (Sparling et al., 1999).  The LD50 was determined to be 3.65 mg/kg.   Exposure to P4 was associated with elevated aspartate aminotransferase, blood urea nitrogen, lactate dehydrogenase, and alanine aminotransferase.  Death occurred in 1-4.5 days, and was related to liver pathology.

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