Metals in feathers of sooty tern, white tern, gray-backed tern, and brown noddy from islands in the North Pacific

Abstract

Levels of heavy metals are usually higher in adult than young birds because they eat larger, more contaminated prey, or because they have had longer to accumulate metals in their tissues. Further, levels of contaminants are usually less in birds nesting on remote, offshore islands than in birds breeding closer to mainland areas that are urbanized and industrialized. We examined the feather levels of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in adult sooty terns (Sterna fuscata), gray-backed terns (Sterna lunata), and brown noddy (Anous stolidus, and adult and young white terns (Gygis alba, from Midway Atoll, and in adult and young sooty terns and adult brown noddy from Manana Island, Hawaii (chicks of other terns were not available). We tested and rejected the null hypotheses that metal levels are not significantly different among species, ages, and locations. Despite their small size, adult white terns had the highest levels of lead, arsenic and tin. Brown noddies had the highest levels of cadmium, chromium, manganese, and selenium. Sooty and white terns had the highest levels of mercury. Sooty tern adults had significantly higher levels of cadmium, mercury, and selenium than young, while young had significantly higher levels of arsenic and manganese. White tern adults had significantly higher levels of selenium and tin than young, while young had higher levels of cadmium and mercury than adults. Except for mercury, there were significant inter-location differences within species in all heavy metals. Contrary to expectation, where the differences were great, metals generally were higher in the feathers of terns and noddies from Midway than from Manana.