24 



(Podiceps grisegena; Fimreite et al. 1971). 

 Four common tern eggs averaged 0.58 ppm 

 and two red-breasted merganser eggs aver- 

 aged 0.81 ppm. 



Aquatic bird eggs from the upper Great 

 Lakes States contained higher mercury levels 

 than those from Louisiana, although species 

 represented from the two areas were not iden- 

 tical (Faber and Hickey 1973). Highest mean 

 residues were in three species of mergansers 

 (up to 1.6 ppm; red-breasted merganser). For 

 those species with all eggs containing less 

 than 0.25 ppm of mercury, the residues were 

 considered to represent background levels. 

 Mercury exceeded 1 ppm in one or more eggs 

 of black-crowned night heron, hooded mer- 

 ganser (Lophodytes cucullatus), common mer- 

 ganser, and red-breasted merganser. Highest 

 levels (up to 1.9 ppm) were in addled eggs of 

 red-breasted mergansers. 



Many birds dependent upon aquatic areas 

 in the Lake St. Clair, Michigan, region have 

 high residues of mercury in their tissues 

 (Dustman et al. 1972). In 1970, carcasses, 

 livers, and eggs were collected and analyzed. 

 Mercury levels in great blue herons (up to 

 175 ppm in the liver; 23 ppm in the carcass) 

 and common terns (up to 39 ppm in the liver; 

 7.5 ppm in the carcass) far exceeded those in 

 any other species. The levels are comparable 

 to those in birds in Sweden that died under ex- 

 perimental dosage with methyl mercury and 

 in birds that died under field conditions in sev- 

 eral Scandinavian countries with signs of mer- 

 cury poisoning (Henriksson et al. 1966; Borg 

 et al. 1969; Holt 1969). Mercury residues in 

 eggs of all of the five common terns (up to 

 6.2 ppm), five of nine mallards (up to 2.7 ppm), 

 three of the five black-crowned night herons 

 (up to 1.1 ppm), and the single egg of a pied- 

 billed grebe (Podilymbus podiceps; 4.0 ppm) 

 were in the range of residues (0.5-3.1 ppm) in 

 eggs of ring-necked pheasants whose repro- 

 ductivity was reduced by mercury in experi- 

 mental studies (Borg. et al. 1969; Fimreite 

 1971; Spannetal. 1972). 



In 1973, eggs of some of these species were 

 again collected at Lake St. Clair, following re- 

 strictions on industrial discharges of mercury 

 into the St. Clair River (Stendell et al. 1976). 

 Mercury levels in the eggs were appreciably 

 lower than were found in these species in 

 1970. Common terns contained the highest 

 residues (up to 1.3 ppm). Mallard eggs con- 



tained relatively low residue levels (<0.05 to 

 0.26 ppm). Black-crowned night heron eggs 

 (up to 0.76 ppm) and great egret eggs (up to 

 0.45 ppm) contained intermediate amounts. 



Mercury levels generally are low in most 

 species of ducks and geese but higher levels 

 have been found in those species that con- 

 sume a greater proportion of animal material 

 in their diet (Kleinert and DeGurse 1972; 

 Krapu et al. 1973; Fimreite 1974; Heath and 

 Hill 1974). Among North American waterfowl 

 species, the highest levels have been found in 

 mergansers. Common mergansers from On- 

 terio had up to 86 ppm mercury in their livers 

 (Fimreite 1974). Hooded mergansers from 

 Clay Lake, Ontario, contained up to 12.3 ppm 

 and common goldeneyes (Bucephala clangula) 

 up to 7.8 ppm in their breast muscle (Vermeer 

 et al. 1973). Food items were also analyzed 

 and crayfish (Oronectes virilis), which the 

 hooded mergansers eat, contained the highest 

 average concentration of mercury (7.1 ppm). 



Mercury has been found in the visceral fat 

 of black-footed albatrosses and Laysan alba- 

 trosses from Midway Atoll, North Pacific 

 Ocean (Fisher 1973). Average residue levels in 

 the Laysan albatrosses were 0.104 ppm and 

 those in the black-footed were 0.075 ppm. 



Mercury has been found in the livers of 

 birds collected around the British coast (Dale 

 et al. 1973). The highest concentration 

 (26 ppm; converted from 122 ppm dry weight, 

 see Holdgate 1971) was in a red-breasted mer- 

 ganser. Common eiders, which feed on 

 mussels that are known to accumulate mer- 

 cury, also had high concentrations (10 ppm). 

 All of the more pelagic species, including 

 black-legged kittiwakes, fulmars, and auks 

 (Alca torda and Alle alle) had less than 

 2.2 ppm. Three gannets had slightly higher 

 levels (up to 2.9 ppm). Herring gulls from 

 oceanic islands contained relatively low mer- 

 cury residues (up to 2.6 ppm) like the pelagic 

 birds, but those from near shore had higher 

 residues. 



Common puffins collected around the coast 

 of Britain contained up to 7.7 ppm (Parslow et 

 al. 1972), and eiders from the Tay region had 

 up to 0.45 ppm mercury in their livers (Jones 

 etal. 1972). 



Elevated levels of mercury have been found 

 in birds of the Baltic region (Jensen et al. 

 1972). In 1969, mercury content of common 

 murre secondaries had doubled the levels 

 from 1906-1325. Mercury levels in murre eggs 



