USGS



BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES
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Biological Characteristics 

Species

The length of the adult common loon (Gavia immer) varies from 66 to 91 cm and the weight varies from 2.5 to 6.1 kg, with males, as an average, being heavier than females (McIntyre and Barr, 1997).  In non-breeding and immature plumages, birds are essentially blackish above and whitish below with some variation on the amount of white showing on the side of the head, and dark traces of a collar are often visible on the sides of the neck (Ferrand, 1989). The loon’s breeding plumage consists of the head, neck, back, wings, and sides black, while the loon is conspicuously marked on scapulars and wing-coverts with large, rectangular white markings; there is a broad patch of vertical white stripes on the side of the neck and a much smaller patch of stripes on the upper foreneck; the breast and the belly are white; the bill is black.  (McIntyre and Barr, 1997).  This loon has a straight dark bill having an even taper, slightly arched culmen. The sexes are similar in appearance (Palmer, 1962). 

Nesting and Status in Estuarine and Coastal Areas

Common loons breed at fresh-water lakes in open and forested regions where they prefer to nest on small islets or in protected areas of promontories and sheltered bays (Palmer, 1962). Lakes larger than 50 acres support territorial pairs, while an abundant supply of fish and water clear enough to allow effective foraging, and lack of human disturbance are important qualities supporting loon breeding habitats (Johnsgard, 1987). Most common loons nest off from the mainland shore of lakes on islands, bog islets, logs, or hummocks. Less than 2% of observed loon nests were on the mainland (Barr, 1986). Nests are a large, wet mass of plant material piled into a flat clump with an average outside diameter of 56 to 57 cm. (McIntyre and Barr, 1997). Successful nests are re-used from year to year (Palmer, 1962). Eggs are subelliptical to oval, size varies geographically. Egg color is olive to brown with dark brown or black splotches. Clutch size is typically 2 eggs (McIntyre and Barr, 1997). Chicks are semiprecocial, but dependent on parents for food, and are dry and active within an hour of hatching, able to enter the water and swim with parents (McIntyre and Barr, 1997).

Abundance and Range

The worldwide population of common loons is estimated at 500,000 to 700,000 in 1996 with the majority of the population in Canada (McIntyre and Barr, 1997). The breeding range includes nearly all of Canada and Alaska south to NE. California, N. Iowa, N. Illinois, N. Ohio, N. Pennsylvania, and Connecticut, and coastal S. Greenland in North America. Iceland is also in the breeding range  (Palmer, 1962). Common loons winter along both east and west coasts of North America and into n. Baja California on the west coast.  In Europe they winter along the Atlantic and North Sea coasts south to the Canary Islands and around the Azores in the Mid-Atlantic (Palmer, 1962).

Site Fidelity

Common loons are migratory throughout their range; no populations are known to breed and winter in the same areas (Strong, 1990).  Annual return rates of 85 to 90 % to the same breeding sites were recorded over a three season period (Meyer et al., 1998).

Ease of Census

Difficult

Feeding Habits

Common loons eat a variety of fish. Fresh-water species such as sticklebacks, trout, and suckers are eaten during breeding season and saltwater species including eels, herring, and haddock are consumed during migration and winter. Common loons find their prey by peering into water while swimming, eyes beneath the surface (McIntyre and Barr, 1997).  Foraging is performed by extended dives and underwater chases with mean diving times ranging from 34 to 64.4 seconds, depending on variables such as water depth, density, size, and elusiveness of prey (Johnsgard, 1987). 

 

Common Loon Contaminant Exposure Data

  I.

Organochlorine Contaminants

A.

Concentrations in adults, juveniles and nestlings

1.

From 1966 to 1972 the Toxic Chemical section of the Canadian Wildlife Service collected a number of bird and egg samples including common loons (Gilbertson and Reynolds, 1973). Tissues from the common loons were analyzed for DDE and PCB with the following concentrations (mg/g , dry wt.) found: Alberta: Brain (n=14, DDE=1.54, PCB=1.38), Liver (n=14, DDE=2.28,  PCB=2.34), Fat (n=14, DDE=23, PCB=16.8).

2.

During 1967 three common loons were collected from lakes in the Superior National Forest in northern Minnesota (Ream, 1976).  The following concentrations (mg/g , lipid wt.) for the three respective loons were found in the listed tissues: Muscle: DDE (4.13, 3.23,1030.88), DDD (1.01, .88, 797.6), DDT (1.11, .91, 69.49), Dieldrin (<.52, <.59, 18.27).   Liver: DDE (4.71, 2.68, 1214.49), DDD (2.25, <.72, 1023.83), DDT (1.12, <.72, 25.36), Dieldrin (<.72, <.72, 23.83).  Brain:  DDE (1.72, 4.83, 552.2), DDD (<.37, 1.48, 265.56), DDT (.49, 2.76, 530.00), Dieldrin (<.37, <.49,  6.56).  Fat: DDE (4.07, 3.22, 1624.43), DDD (.65, 1.59, 685.52), DDT (1.48, .68, 1469.01), Dieldrin (<.02, <.03, 5.44). 

3.

Between 1968 and 1979, 215 common loon carcasses (185 healthy, 30 sick or emaciated, 207 drowned, 4 shot, 1 strangled, 3 with fish hooks) were collected across Ontario, Canada (Frank et al., 1983).  Individual carcasses were divided into specific tissue samples as follows:

One group of loon carcasses collected from 1971 to 1974 (n = 157) were divided into brain (b), liver (l), pectoral muscle (m), and body fat (f) samples. The mean concentrations (mg/g , wet weight) for 128 healthy birds found were as follows and listed in the order of (b,l,m,f): SDDT: Juvenile n=21 (0.18, 0.27, 0.81, 12.5), Male adult n=49 (0.83, 1.67, 2.32, 58.0), Female adult n=58 (0.79, 2.05, 2.32, 70.6).  Dieldrin: Juvenile (0.01, 0.02, 0.06, 0.83), Male adult (0.04, 0.10, 0.09, 1.92), Female adult (0.06, 0.14, 0.13, 4.02).  PCB:  Juvenile (0.61, 0.75, 1.78, 29.2), Male adult (1.77, 4.20, 4.47, 103), Female adult (1.98, 5.52, 4.39, 126).  The mean concentrations for 29 emaciated birds were as follows: SDDT: Juvenile  n=6 (35.6, 78.1, 12.6, 452), Male adult n=13 (25.2, 35, 16.3, 1008), Female adult n=10 (27.9, 36.3, 11.7, 754).  Dieldrin: Juvenile (1.23, 0.79, 0.13, 11.9), Male adult (0.48, 0.41, 0.16, 8.23), Female adult (0.81, 1.01, 0.24, 10.7).  PCB:  Juvenile (45.5, 68.9, 10.1), Male adult (58.5, 87.1, 23.4, 1224), Female adult (62.9, 81.8, 19.8, 1570).             

A second group of loon carcasses collected from 1971 to 1974 (n = 103) were divided into body fat (f), uropygial gland (ug), uropygial oil (uo), back feather (bk) and belly feather (bl) samples. The mean concentrations (mg/g , wet weight) for 87 healthy birds found were as follows and listed in the order of (f, ug, uo, bk, bl): SDDT: Juvenile n=15 (16.5, 7.53, 7.45, 0.18, 0.14),  Adult n=72 (80.6, 42.7, 34.7, 1.17, 0.32).  Dieldrin: Juvenile (1.09, 0.63, 0.34, trace, 0.01), Adult (3.63, 1.34, 1.06, 0.03, 0.01).  PCB:  Juvenile (39.2, 8.76, 29.9, 0.56, 0.34), Adult (144, 43.3, 104, 3.75, 1.80).  The mean concentrations for 16 emaciated birds were as follows: SDDT: Juvenile, n=3 (541, 70.5, 300, 8.9, 4.08), Adult n=13 (1198, 280, 470, 3.64, 1.62).  Dieldrin: Juvenile (4.85, 1.22, 2.54, 0.38, 0.12), Adult (10.9, 4.42, 5.82, 0.02, 0.01).  PCB:  Juvenile (783, 255, 275, 6.78, 4.33), Adult (1696, 394, 549, 13.4, 4.55).                                                

A third group of loon carcasses collected from 1971 to 1974 (n = 31) were divided into the following internal body organ and tissue components: gizzard (g), intestine (i), blood (b), liver (l), heart (h), lung (lu), brain (br), kidney (k). Mean concentrations (mg/g , wet weight) were found as follows: SDDT: healthy juveniles (n=8) (g=0.38, i=0.78, b=0.03, l=0.11, h=0.54, lu=0.15, br=0.07, k=0.09), healthy adults (n=13) (g=3.33, i=2.92, b=0.11, l=1.25, h=4.34, lu=0.77, br=0.83, k=0.45), emaciated adults (n=10) (g=5.45, i=15.8, b=1.75, l=25.3, h=9.64, lu=4.04, br=20.5, k=20.0).  Dieldrin: healthy juveniles (n=8) (g=0.03, i=0.07, b=ND, l=0.01, h=0.02, lu=trace, br=trace, k=trace), healthy adults (n=13) (g=0.08, i=0.17, b=trace, l=0.02, h=0.05, lu=0.01, br=0.02, k=0.01), emaciated adults (n=10) (g=0.18, i=0.34, b=0.01, l=0.43, h=0.07, lu=0.04, br=0.53, k=0.31). PCB: healthy juveniles (n=8) (g=0.88, i=2.12, b=0.04, l=0.29, h=1.08, lu=0.14, br=0.21, k=0.20), healthy adults (n=13) (g=3.94, i=7.40, b=0.24, l=2.53, h=9.72, lu=2.68, br=1.66, k=1.97), emaciated adults (n=10) (g=10.6, i=35.4, b=2.33, l=101, h=37.3, lu=13.1, br=76.4, k=58.7).  

4.

Liver, brain and fat samples from 14 common loons were collected in Alberta, Canada from 1969 to 1972 (Falandysz and Szefer, 1982). The following mean concentrations (mg/g , wet weight) were found: PCB in liver (2.3), PCB in brain (1.4), PCB in Fat (17), SDDT in liver (2.3), SDDT in brain (1.5), SDDT in fat (23). One individual loon collected in Port Alexander, British Columbia had a fat SDDT concentration of 0.42 mg/g .

5.

From 1971 to 1975 liver and muscle tissue were collected from common loons found dead at various sites (Bourne and Bogan, 1976). The following are the concentrations (mg/g, wet weight) found: North Britain, n = 3, DDE in liver (2.0, 1.8, 0.5), DDE in muscle (1.0, 1.0, 1.0), PCB in liver (2.0, 14.2, 2.8), PCB in muscle (1.0, 6.5, 5.4); Jersey, England, n = 2, DDE in liver (6.1, 14.5), DDE in muscle (1.7, 2.1), PCB in liver (28.1, 25.3), PCB in muscle (6.1, 3.4), Dieldrin in liver (0.5, 0.7), Dieldrin in muscle (1.0, 0.2); Massachusetts, n = 1, DDE in liver (0.1), PCB in liver (0.4). 

6.

Between 1972 and 1999, dead or debilitated common loons (n = 105) were collected in New York (Stone and Okoniewski, 2001).  Of the 105 loons, 39 were chosen for analysis of organochlorines in brain tissue (geometric mean concentration) with the following results: DDE, occurred in 92% of samples, 0.47 mg/g, wet weight; PCB occurred in 92% of samples, (2.02); Dieldrin occurred in 79% of samples, (0.06); Oxychlordane occurred in 64% of samples, (0.02); trans-Nonachlor occurred in 53% of samples, (0.02); Heptachlor epoxide occurred in 51% of samples, (0.01); and Mirex occurred in 49% of the samples, (0.02).  The highest PCB concentration (60) was found in an emaciated adult male loon, while the highest DDE concentrations (11) was found in a thin adult female loon succumbing to fish hook ingestion. 

7.

A moribund common loon (female, subadult weighing 4 lbs.) was found in Madison County, Mississippi in December 1973 (Prouty et al., 1975). After dying, the loon carcass and a separate brain sample were analyzed for organochlorine contaminants (mg/g, wet weight, ND=not detected, NA=not analyzed) with the following results listed as (carcass, brain): p,p’-DDE (680, 130),  p,p’-DDD  (1400, 200),  p,p’-DDT (10, 2.1),  Dieldrin (0.18, ND), p,p'-DDD-olefin (67, NA),  p,p’- Dichlorobenzophenone (DCBP) (5, ND),  p,p’-DDMS (34, NA),  o,p’-DDD (33, NA),  o,p’-DDE (55, NA), Dicofol (26, NA),  PCB (180, 15).

8.

A total of 68 oiled common loons were collected between late January and 23 March 1979 from the coasts of Shetland, UK following the Esso Bernicia oil spill and the carcasses were placed in frozen storage (Heubeck et al., 1993). Later, pectoral muscle and liver tissue from 12 randomly selected loons were analyzed for organochlorine residues and mercury. The following mean concentrations in mg/g, wet weight were found: DDE in muscle (0.84), DDE in liver (1.46), PCB in muscle (1.05), PCB in liver (2.99).

9.

On 4 November 1981, 4 loons were found dead and 2 birds were randomly selected for analytical toxicology (Coppock and Somers, 1990). The body fat was analyzed for organochlorine contamination with the following concentrations found in ug/g: loon A- PCB=93, dieldrin=3.0; loon B- PCB=101, dieldrin=1.4. No other organochlorine compounds were detected.  

10.

Brain tissue samples (n=13) were collected from dead common loons (n=173) during an epizootic along the north Gulf Coast of Florida from January to March 1983 in which more than 13,000 loons were estimated to have died (Forrester et al. 1997). Residues of DDE and PCBs (Aroclor 1260) were found in all brain samples, the mean concentrations (mg/g, wet weight) were: DDE = 7.8, Aroclor 1260 = 23.  Low concentrations (< 1) were found of dieldrin (n=7), heptachlor epoxide (n=6), oxychlordane (n=6), trans-nonachlor (n=6), and cis-chlordane (n=1). Residues of other organochlorine compounds were not detected.

 11.

Muscle and brain tissue samples were collected from common loons found dead in northern Wisconsin from 1984 to 1987 (Belant and Anderson, 1990). The following concentrations in mg/g, wet weight, were found in individual loons and are listed as (muscle/brain):  Bayfield County, Adult 1: PCB (3.3/0.59), dieldrin (0.19/0.03), DDE (0.98/0.16); Adult 2, PCB (3.4/0.49), dieldrin (0.06/<0.02), DDE (0.61/0.07); Adult 3, PCB (3.2/0.3), dieldrin (0.22/0.03), DDE (0.77/0.06).  Portage County, Juvenile: PCB (2.2/0.46), dieldrin (0.07/0.02), DDE (0.43/0.09).  Iron County, Adult: PCB (18.0/29.0), dieldrin (0.88/2.20), DDE (4.7/7.7).  Vilas County, Adult (muscle only): PCB (26.0), dieldrin (2.0), DDE (7.0).

12.

A liver sample from a juvenile common loon weighing 1684 grams and found dead near Cley-next-the-Sea, Norfolk, England on 13 November 1985 was analyzed for organochlorines (Mason and MacDonald, 1988). Concentrations in mg/g were found for the following compounds: PCBs (0.24), dieldrin (5.15), lindane (4.01), DDE (8.99), DDT (1.78).

13.

Livers (n=13) selected from 75 common loons found dead or moribund from 1989 to 1990 at fresh-water lakes throughout New England (Maine n=14, New Hampshire n=31, Vermont n=1), and in coastal shorelines of Maine (n=2) and Massachusetts (n=27), were analyzed for organochlorine contamination (Pokras et al., 1991).  The following mean concentrations (mg/g wet weight) were found (adult n=8, immature n=5): DDE (3.8, 1.9), DDT (0.4, 0.1), PCB 1248 (0.8, 0.8), PCB 1260 (14.7, 8.7).     

14.

Common loons (n=124) found dead or moribund from 1989 to 1992 were collected throughout New England (Pokras et al., 1992). Liver samples from 16 loons (8 adults, 5 juveniles, and 3 chicks) had the following mean concentrations (mg/g, wet weight) and listed in order of (adults, juveniles, chicks): DDE (3.89, 1.94, 1.31); DDT (0.43, 0.14, 0.07); PCB 1248 (15.27, 9.43, 3.45); PCB 1254 (24.45, 40.95, 4.09); PCB 1260 ( 0.29, trace, trace); dieldrin (0.04, 0.12, 0.16); oxychlordane (0.10, 0.05, 0.03); trans-nonachlor (0.16, 0.09, 0.40).

15.

Livers from common loons found dead at wildlife refuges or that had died at rehabilitation centers during 1997 to 1998 were analyzed for perfluorooctane sulfanate (PFOS) (Kannan et al. 2001).  The following mean concentrations (ng/g, wet weight) were found: Carteret County, NC (n =5, 1 adult and 4 juvenile), 280; Monterey Bay, CA (n = 4, 4 adult), 37;  Pompano, FL (n=4, 3 adult, 1 juvenile), 40 ;  Ft Lauderdale, FL (n = 1, subadult), 115 ;  Carlsbad, CA (n = 1),   < 12 ;  San Diego, CA 11/97 (n = 2), 62 ; Coronado, CA (n = 1), 451 ;  San Diego, CA 12/97 (n = 1), 112.

B.

Concentrations in eggs

1.

From 1966 to 1972 the Toxic Chemical section of the Canadian Wildlife Service collected a number of bird and egg samples including common loons (Gilbertson and Reynolds, 1973). Eggs from common loons contained the following mean concentrations (mg/g dry weight): Alberta (n=17, DDE=7.53, PCB=5.43), Saskatchewan (n=5, DDE=54.4, PCB=87.9).

2.

During 1967, 5 common loon eggs were collected from the Superior National Forest in northern Minnesota (Ream, 1976).  The following concentrations (mg/g lipid weight) were found for the five eggs respectively: DDE (176.29, 323.88, 240.51, 223.83, 173.31), DDD (5.96, .64, 16.95, 12.89, 19.23), DDT (16.26, 1.80, 40.89, 32.55, 25.04), dieldrin (4.97, 16.19, 8.26, 4.56, 5.97).  

3.

Between 1968 and 1980, 98 common loon eggs were collected from active nests at locations in Ontario, Canada (Algonquin, Kinoje Lake, Algonquin Parry Sound) (Frank et al., 1983). The following are the years and mean concentrations (mg/g wet weight) found: DDE: 1968, n = 4, (41.4); 1969, n = 14, (8.6); 1970, n = 34, (33.6); 1972, n = 15, (24.8); 1978, n = 12, (6.6); 1980, n =19, (3.98). DDD: 1968 (6.3), 1969 (1.7), 1970 (2.3), 1972 (0.0), 1978 (0.17), 1980 (0.36).  DDT:  1968 (4.7), 1969 (1.7), 1970 (2.3), 1972 (0.1), 1978 (0.0), 1980 (0.0).  Dieldrin:  1968 (0.24), 1969 (0.58), 1970 (1.55), 1972 (0.74), 1978 (0.08), 1980 (0.26).  HE: 1978 (0.05), 1980 (0.07).  Chlordane: 1978 (0.05), 1980 (0.21).  PCB:  1970 (33), 1972 (65), 1978 (10.5), 1980 (6.1).  HCB: 1978 (0.01), 1980 (0.01).  Mirex: 1978 (0.49), 1980 (0.23).

4.

Common loon eggs (n=17) were collected in Alberta, Canada from 1969 to 1972 (Falandysz and Szefer, 1982). The following mean concentrations (mg/g wet weight) were found: PCB (5.4), SDDT (7.5).

5.

A common loon egg was collected from each of 15 clutches in the Lac La Biche- St. Paul region of Alberta, Canada during 1972 (Vermeer, 1973).  Eggshell thickness was also measured to see if a correlation could be found between thickness and contaminant concentrations. The following mean concentrations were found (mg/g wet weight): PCB = 1.2, DDE = 1.7, DDD = trace, DDT = trace, dieldrin = trace, endrin = trace, heptachlor epoxide = trace, benzene hexachloride = trace. The following are the individual egg DDE concentrations for the 15 eggs: (4.82, 1.28, 1.02, 0.84, 1.38, 1.55, 0.89, 2.06, 1.19, 2.31, 1.07, 1.09, 1.16, 3.03, 1.31).  The PCB and organochlorine residues in loon eggs were low compared to those found in 1968 in other fish-eating birds in Alberta.

6.

From 1974 to 1975 common loon eggs (n=31) were collected from Hanson Lake, Saskatchewan (Fox et al., 1980).  The following geometric mean concentrations (mg/g wet weight ) were found: DDE (5.80), DDD (0.10), DDT (0.08), dieldrin (0.43), heptachlor epoxide (0.08), HCB (0.06), PCBs (14.10). The values from this study were compared with other studies, including unpublished data on loon eggs from Ontario, Canada (n=7) as follows: DDE (6.6), dieldrin (0.28),  PCBs (9.5).

7.

Common loon eggs (n=51) from 3 New Hampshire lakes were collected from 1975 to 1976 after they had either been abandoned following disturbance, abandoned after prolonged incubation, or knocked into the water by an incubating adult (Sutcliffe, 1978). Of the 51 eggs collected, 14 eggs were analyzed for organochlorine content with the following geometric means recorded (mg/g wet weight): DDE (5.88), DDT (2.44), dieldrin (0.105), total PCB (24.6), DDD (<0.05), PCB as Arochlor 1254 (n=8, 18.30). A significant correlation was noted between PCB and DDE residues.                                                                                                         The geometric mean concentrations from these 14 New Hampshire eggs were then compared to concentrations found in eggs from other studies. The comparison values are as follows (total PCB was not included): 1975 North Central Minnesota (n = 9): DDE (4.99), DDT (0.51), dieldrin (0.29), DDD (1.28), PCB as Arochlor 1254 (12.7).  1975 New Hampshire study (n = 3): DDE (4.76), DDT (0.17), Dieldrin (0.26), PCB as Arochlor 1254 (20.39).  1975 Saskatchewan (n = 7): DDE (6.28), DDT (0.99), Dieldrin (0.29), PCB as Arochlor 1254 (14.7).  1973 Alberta (n = 15): DDE (1.7), PCB as Arochlor 1254 (1.2).

8.

Non-viable common loon eggs were collected from 15 locations on six New Hampshire lakes and from 28 lakes in the Adirondacks of New York from 1978 to 1986 (McIntyre et al., 1992). The following mean concentrations (mg/g wet weight) were found and are listed in the order of years (1978 n=13, 1979 n=5, 1980 n=8, 1982 n=2, 1984 n=12, 1985 n=14, 1986 n=9): dieldrin (0.22, 0.10, 0.14, 0.15, 0.15, 0.20, 0.05); total chlordane (0.35, 0.23, 0.28, 0.38, 0.34, 0.41, 0.09); total DDT (3.91, 2.42, 2.43, 1.97, 1.94, 2.48, 0.74); total PCB (10.73, 3.83, 4.65, 7.42, 4.96, 5.59, 1.79); mirex (0.07, NA, 0.03, 0.05, NA, 0.07, NA); HCB (ND, ND, ND, ND, 0.009, 0.010, 0.004).  Mean concentrations were also compared by location collected between 1983 and 1985 and listed as (New Hampshire n=15 / New York n=26): dieldrin (0.10 / 0.17); chlordane (0.24 / 0.38); SDDT (1.59 / 2.21); PCBs (3.96 / 5.29); HCB (NA / 0.01) mirex (NA / 0.08).

9.

Non-viable common loon eggs were collected from Stillwater reservoir, New York from 1978 to 1986 (McIntyre et al., 1992).  The following mean concentrations (mg/g wet weight) were found and listed as (1978 n=8 / 1986 n=9): dieldrin (0.189 / 0.059); chlordane (0.336 / 0.101); total DDT (3.375 / 0.846); total PCBs (7.30 / 1.833).  Mean concentrations of DDT for individual eggs was as follows: 1978 (5.55, 5.18, 3.08, 2.36, 2.89, 1.76, 3.14. 3.04); 1980 (1.61, 1.10, 0.63); 1982 (1.59) ; 1984 (2.61, 2.38), 1985 (2.17, 2.65), 1986 (0.75, 0.69, 1.33, 0.56, 1.42, 0.46, 0.47, 0.60, 2.1). Mean concentrations of PCBs for individual eggs were as follows: 1978 (9.2, 8.1, 3.6, 3.7, 12.0, 9.7, 4.9, 7.2) ; 1980 (2.4, 2.6, 4.4) ; 1982 (5.0) ; 1984 (6.1, 6.6) ; 1985 (5.1, 7.2) ; 1986 ( 2.3, 1.9, 2.4, 1.5, 0.66, 1.3, 1.4, 1.6, 2.0).

10.

Failed eggs were collected from New Hampshire common loon nests in 1979 (n=15) and 1981 (n=21) (Haseltine et al., 1983). The following are the geometric mean concentrations (mg/g, wet wt.) found, listed in order of (1979, 1981): DDE (2.9, 1.9), DDD (0.09, 0.08), dieldrin (0.10, 0.09), oxychlordane (0.07, 0.06), cis-chlordane (0.06, 0.07), trans-nonachlor (NA, 0.13), cis-nonachlor (0.05, 0.05), PCB (10, 6.28). The two principal contaminants of loon eggs, DDE and PCBs, decreased significantly between sampling periods.

11.

Common loon eggs (n = 12) were collected at Turtle-Flambeau Flowage in Iron County, Wisconsin from 1986 to 1987 (Belant and Anderson, 1990). The mean concentrations (n=12) were: PCB = 4.04 mg/g wet weight, dieldrin = 0.47 mg/g, DDE = 1.22 mg/g.

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

A.

Concentrations in adults, juveniles and nestlings

1.

Between 1968 and 1979, 215 common loon carcasses (185 healthy, 30 sick or emaciated) were collected across Ontario, Canada (Frank et al. 1983). Individual carcasses were divided into specific tissue samples and analyzed Hg as follows:  One group of loon carcasses collected from 1971 to 1974 (n = 157) were divided into brain (b), liver (l), pectoral muscle (m), and body fat (f) samples. The mean concentrations (mg/g wet weight) for 128 healthy birds found were as follows and listed in the order of (b,l,m,f): Juvenile  (0.44, 1.92, 0.79, 0.15), Male adult (0.57, 6.35, 1.14, 0.22), Female adult (0.51, 5.04, 1.02, 0.22). The mean concentrations for 29 emaciated birds were as follows: Juvenile  (1.82, 26.4, 5.41, 0.21), Male adult (1.04, 16.3, 3.26, 0.47), Female adult (1.03, 19.0, 2.71, 0.65).               

A second group of loon carcasses collected from 1971 to 1974 (n = 103) were divided into body fat (f), uropygial gland (ug), back feather (bk) and belly feather (bl) samples. The mean concentrations (mg/g wet weight) for 87 healthy birds found were as follows and listed in the order of (f, ug,  bk, bl): Juvenile (0.18, 0.30, 5.0, 4.74), Adult (0.24, 0.30, 3.75, 10.7).  The mean concentrations for 16 emaciated birds were as follows: Juvenile (0.22, 1.49, 12.9, 19.4), Adult (0.48, 0.59, 13.4, 14.9).         

A third group of loon carcasses collected from 1971 to 1974 (n = 31) were divided into the following internal body organ and tissue components: gizzard (g), intestine (i), blood (b), liver (l), heart (h), lung (lu), brain (br), kidney (k). Mean concentrations (mg/g wet weight) were as follows: healthy juveniles (n=8) (g=0.87, i=0.73, b=0.93, l=1.73, h=0.62, lu=0.55, br=0.44, k=1.12), healthy adults (n=13) (g=1.00, i=0.77, b=1.74, l=5.32, h=1.10, lu=1.08, br=0.65, k=6.58), emaciated adults (n=10) (g=1.62, i=2.43, b=2.52, l=17.0, h=1.76, lu=1.90, br=0.95, k=22.0). 

2.

Common loons were among 184 specimens that were collected (shot) between 20 July and 05 August 1970 and between 20 June and 28 July 1971 from lakes along the Wabigoon River in Ontario, Canada (Fimreite, 1974). Liver and breast samples were analyzed for Hg: Ball Lake (n=4 adult loons) 51.9 mg/g wet wt. Hg; Sydney Lake (n=3 adult loons) 10.3 Hg. Mean liver and breast concentrations (n=5) for selected loons from northwestern Ontario were liver 43 and breast 14.9. The concentration of Hg in the breast muscle correlated to the concentration of Hg in the liver samples.

3.

From 1970 through 1994, primarily during December to April, common loons found sick or dead on Florida beaches were collected, the carcasses (n=434) were examined for cause of death, and the livers and kidneys of some individuals were analyzed for trace metal contamination (Forrester et al. 1997). Many of the carcasses examined (n=173) were obtained during an epizootic that occurred from January to March 1983 along the north Gulf Coast in which more than 13,000 loons were estimated to have died. The following concentrations were found for the dates and areas indicated, listed as (Hg/Se, number of samples): Atlantic Coast: Emaciated Loons: 1987 (2.3/NA, n=9), 1990-1991 (1.4/NA, n=2), 1993 (4.8/NA, n=2), 1994 (4.3/NA, n=5); Oiled Loons: 1974 (5.2/7.3, n=6).  Gulf Coast: Emaciated Loons: 1973-1974 (17/12, n=5), 1974-1975 (13/6.8, n=6), 1983 (22/10, n=13), 1984 (7.9/8.7, n=1), 1991 (7.7/NA, n=8); Normal Loons: 1984 (4.5/5.8, n=23).   Residues of Hg and Se in livers of male and female loons were not significantly different, however residues of Hg were significantly higher in loons from the Gulf Coast than loons from the Atlantic Coast, (Se was not compared because Atlantic emaciated loons were not tested for Se). Residues of both Hg and Se were higher in emaciated loons than in normal birds and there was a linear correlation between residues of Hg and Se.

4

Between 1972 and 1999, dead or debilitated common loons (n = 105) were collected in New York (Stone and Okoniewski, 2001).  Concentrations of Hg were determined in the livers of 82 loons and ranged from 0.07 mg/g wet weight, in a Pb-poisoned unfledged chick, to 371 mg/g in an adult female with air sacculitis. The geometric mean Hg concentration for all 89 liver samples was 10.3 mg/g. Lead fishing weights were found ingested by 21 loons and Pb in livers of these loons exceeded the 5 to 6 mg/g thresholds for lethal Pb poisoning determined for waterfowl. The mean concentration of Pb in loons not digesting Pb sinkers (n=48) was 0.07, with 21 loons having hepatic Pb concentrations below detection limits. .

5.

In 1976 common loons (38 adults, 11 chicks) were collected (adults shot) from various lakes in northwestern Ontario, Canada (Barr, 1986). The 34 lakes within the Wabigoon-English River watershed were grouped in 4 classes according to proximity to Hg contamination sources. C1 lakes are directly downstream of a Hg contamination source, C2 lakes are not within the flow of contaminated waters but are accessible to contaminated fish, C3 are upstream of the contamination source, and C4 are independent control lakes. The following concentrations (mg/g wet weight) were found in the various tissues listed as (Hg/MeHg): C1 lakes (5 adults, 1 chick): Adult liver (29.73/1.53), Chick liver (1.28/0.97), Adult muscle (4.57/2.32), Chick muscle (0.89, 0.80), Adult brain (1.49/0.76), Chick brain (0.78/0.75).  C2 lakes (4 adults, no chicks): Adult liver (16.65/1.09), Adult muscle (3.41, 1.59), Adult brain (1.15, 0.50).  C3 lakes (12 adults, 6 chicks):  Adult liver (5.10/1.04), Chick liver (0.91/0.84), Adult muscle (1.22/1.04), Chick muscle (0.38/0.33), Adult brain (0.42/0.39), Chick brain (0.30/0.30).  C4 lakes (10 adults, 4 chicks):  Adult liver (8.81/0.20), Chick liver (0.83/0.71), Adult muscle (1.20/0.85), Chick muscle (0.42/0.30), Adult brain (0.43/0.33), Chick brain (0.37/0.37).                                   

For all lake locations combined (37 adult loons, 10 chicks) the Hg/MeHg concentrations were as follows: Adult liver (12.95/11.67), Chick liver (0.91/0.80), Adult muscle (2.33/1.65), Chick muscle (0.44/0.37), Adult brain (0.86/0.65), Chick brain (0.37/0.37).          

Mercury concentrations were significantly higher in brains of nesting loons from C1 lakes 150 to 320 km downstream in the path of waterborne Hg and from C2 lakes, although not significantly different from each other, were significantly higher than in loons from C3 and C4 lakes, which were not significantly different than each other. The concentration of total Hg residue in loon tissues decreased in the sequence liver>muscle>brain but the percentage of MeHg increased from liver<muscle<brain. Adult male loons generally contained higher levels of Hg than did their mates or other females from the same lake class.  

6.

Common loons were collected from 3 locations in New England (Locke et al., 1982).  A loon found dead on September 6, 1976 at Squam Lake, New Hampshire (female, with an ingested Pb fishing sinker) was divided into various samples for Pb analysis as follows (mg/g wet weight): femur (39.22), heart (0.91), blood clot from heart (9.91), lung (2.34), spleen (3.24), cerebrum (1.40), cerebellum (1.02), liver (20.6), kidney (61.4).  Another loon found dead on May 13, 1980 at Little Lake, Wisconsin (male, with an ingested Pb fishing sinker) had the following Pb concentrations: liver (46.1) and kidney (15.7).  A third loon found dead at Indian Lake, Maine on July 16, 1979 (male, no ingested lead found) contained a lead liver concentration of 38.52 mg/g. Lead concentrations in livers of 13 common loons dying from causes other than lead poisoning were all <1 mg/g.

7.

A total of 68 oiled common loons were collected between late January and 23 March 1979 from the coasts of Shetland, UK following the Esso Bernicia oil spill (Heubeck et al., 1993). Twelve randomly selected loons contained 0.61 mg/g wet weight Hg in pectoral muscle and 15.03 mg/g in liver.

8.

On 4 November 1981, 4 loons were found dead and 2 birds were randomly selected for analytical toxicology (Coppock and Somers, 1990). The liver from one loon was contained 0.50 mg/g Pb and 0.25 mg/g Hg.

9.

Livers and breast feather samples from 221 common loons were collected between 1984-90 from 18 counties in the northern and central portions of Minnesota (Ensor et al., 1992). All loons had detectable hepatic Hg, with a range of 0.08 to 83 mg/g wet weight and a geometric mean value of 3.6 mg/g, while feather concentrations ranged from 0.05 to 29 mg/g and a