Influence of species, age and diet on mercury concentrations in Shetland seabirds

Abstract

Chick down, chick feathers and feathers from adults of 5 seabird species (Arctic skua Stercorarjus parasiticus, great skua Cdtharacta skua, Arctic tern Sterna paradjsaea, kittiwake Rissa tridactyla, and common guillemot Uria aalge) were analysed for mercury. Individual female Arct~c and great skuas' body feather mercury concentrations correlated wlth concentrations in their chicks' down, but not feathers (Arctic skua. r = 0.64; great skua: r = 0.66) This demonstrated that mercury in chick down originated from the egg, and that mercury in the egg and In adult females' plumage could have the same dietary source. Inter-specific differences in mercury concentrations were found for all age classes sampled, and these could be explained partly in terms of dietary specialisation, although physiological variations may also be important. All 3 age classes of great skua showed a direct incl-ease in mercury with increasing proportion of bird meat in the diet of individual pairs. In kittiwake, Arctic skua and great skua, adults had higher mercury concentrations than chicks and ch~ck down had higher concentratlons than chick feathers. However, In 2 species (Arctic terns and guillemots) chick down had higher concentrations than adult feathers. Chick dnlvn could be sampled for mercury content d s an alternative to using eggs in national biomonitoring xhernes. Feathered chicks could be sa~iipled to determine mercury availability around the breedlng colony between hatching and fledging.

Arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in feathers of Black-legged Kittiwake (Rissa tridactyla) and Black Oystercatcher (Haematopus bachmani) from Prince William Sound, Alaska

“…In a review of metal levels in feathers, Burger (1993) reported that adults had significantly higher levels than young of the year for cadmium (3 of 5 studies), lead (4 of 7), manganese (5 of 5), mercury (20 of 21), and selenium (3 of 3), with chromium showing less of a pattern (1 of 4 studies). Since that paper was published, differences, differences between adults and young have been reported for other species and metals (Stewart et al, 1997;DeBacker et al, 2001; and reviewed in Burger and Gochfeld, 2002). The differences between adults and young likely reflect differences due to exposure in different places.…”

“…Because some pollutants undergo biomagnification up the food chain, and can accumulate with age, concentrations are generally higher in top trophic level birds and mammals (Lewis and Furness, 1991;Ohlenhdorf, 1993;Bargagli et al, 1998;Scheifler et al, 2005). Factors that affect uptake, accumulation, and biomagnification of metals in birds include exposure pathways, species of the metal, and bioavailability, as well as a number of host factors, such as trophic status, location, foraging behavior, nutrition, body condition, gender, size, genetic variability, and age (Stewart et al, 1997;Debacker et al, 2001;Burger et al, 2003). Marine birds are exposed to a wide range of chemicals because they occupy a wide range of trophic levels, and those at the top of the food chain are susceptible to bioaccumulation of pollutants (Furness and Rainbow, 1990;Lewis and Furness, 1991;Burger and Gochfeld, 2002;Nygard et al, 2001).…”

Comparison of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in feathers in bald eagle (Haliaeetus leucocephalus), and comparison with common eider (Somateria mollissima), glaucous-winged gull (Larus glaucescens), pigeon guillemot (Cepphus columba), and tufted puffin (Fratercula cirrhata) from the Aleutian Chain of Alaska

“…A number of studies with several species of seabirds have examined trophic level relationships, and found increasing mercury levels with increasing trophic level (Hahn et al 1993;Stewart et al 1997;Burger andGochfeld 1997, 2000a;Borga et al 2006). However, no trophic level relationships have been found in a number of studies for manganese (Borga et al 2006), and selenium (Sydeman and Jarman 1998;Borga et al 2006).…”

Variability in mercury concentrations of great skuas Catharacta skua:the influence of colony, diet and trophic status inferred from stable isotope signatures

“…Whereas foraging area, moult, age, sex and season have been argued as potential sources (e.g. Walsh 1990), only recently has dietary specialisation within a species been considered (Stewart et al 1997), and the possible influences of differences in migratory habits and physiology within a species have been somewhat neglected. Since mercury is the only heavy metal in which there is good evidence for biomagnification up food chains (Bryan 1979, Atwell et al 1998, Monteiro et al 1998, it seems likely that within a species individuals feeding at higher trophic levels would have higher mercury levels in their tissues (Thompson et al 1998).…”