Mercury and other metals in eggs and feathers of glaucous-winged gulls (Larus glaucescens) in the Aleutians

Levels of mercury and other contaminants should be lower in birds nesting on isolated oceanic islands and at high latitudes without any local or regional sources of contamination, compared to more urban and industrialized temperate regions. We examined concentrations of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in the eggs, and the feathers of fledgling and adult glaucous-winged gulls (Larus glaucescens) nesting in breeding colonies on Adak, Amchitka, and Kiska Islands in the Aleutian Chain of Alaska in the Bering Sea/North Pacific. We tested the following null hypotheses: 1) There were no differences in metal levels among eggs and feathers of adult and fledgling glaucous-winged gulls, 2) There were no differences in metal levels among gulls nesting near the three underground nuclear test sites (Long Shot 1965, Milrow 1969, Cannikin 1971) on Amchitka, 3) There were no differences in metal levels among the three islands, and 4) There were no gender-related differences in metal levels. All four null hypotheses were rejected at the 0.05 level, although there were few differences among the three test sites on Amchitka. Eggs had the lowest levels of cadmium, lead, and mercury, and the feathers of adults had the lowest levels of selenium. Comparing only adults and fledglings, adults had higher levels of cadmium, chromium, lead and mercury, and fledglings had higher levels of arsenic, manganese and selenium. There were few consistent interisland differences, although levels were generally lower for eggs and feathers from gulls on Amchitka compared to the other islands. Arsenic was higher in both adult feathers and eggs from Amchitka compared to Adak, and chromium and lead were higher in adult feathers and eggs from Adak compared to Amchitka. Mercury and arsenic, and chromium and manganese levels were significantly correlated in the feathers of both adult and fledgling gulls. The feathers of males had significantly higher levels of chromium and manganese than did females. The levels of most metals in feathers are below those known to be associated with adverse effects in the gulls or their predators. However, levels of mercury in some gull eggs are within a range suggesting that several eggs should not be eaten in one day by sensitive humans.     

Assessment of metals in down feathers of female common eiders and their eggs from the Aleutians: arsenic, cadmium, chromium, lead, manganese, mercury, and selenium

Concentrations of arsenic, cadmium, chromium, lead, manganese, mercury and selenium were examined in the down feathers and eggs of female common eiders (Somateria mollissima) from Amchitka and Kiska Islands in the Aleutian Chain of Alaska to determine whether there were (1) differences between levels in feathers and eggs, (2) differences between the two islands, (3) positive correlations between metal levels in females and their eggs, and (4) whether there was more variation within or among clutches. Mean levels in eggs (dry weight) were as follows: arsenic (769 ppb, ng/g), cadmium (1.49 ppb), chromium (414 ppb), lead (306 ppb), manganese (1,470 ppb), mercury (431 ppb) and selenium (1,730 ppb). Levels of arsenic were higher in eggs, while chromium, lead, manganese, and mercury were higher in feathers; there were no differences for selenium. There were no significant interisland differences in female feather levels, except for manganese (eider feathers from Amchitka were four times higher than feathers from Kiska). Levels of manganese in eggs were also higher from Amchitka than Kiska, and eider eggs from Kiska had significantly higher levels of arsenic, but lower levels of selenium. There were no significant correlations between the levels of any metals in down feathers of females and in their eggs. The levels of mercury in eggs were below ecological benchmark levels, and were below human health risk levels. However, Aleuts can seasonally consume several meals of bird eggs a week, suggesting cause for concern for sensitive (pregnant) women.     

Heavy metal and selenium levels in birds at Agassiz National Wildlife Refuge,Minnesota: Food chain differences

The levels of heavy metals and selenium in the eggs and in breast feathers of adult doublecrested cormorant (Phalacrocorax auritus), black-crowned night heron (Nycticorax nycticorax), and franklin's gull (Larus pipixcan) nesting at Agassiz National Wildlife Refuge in Marshall County, northwestern Minnesota were examined. Also examined were metal levels in the feathers of fledgling night herons and gulls, in the feathers of adult and fledgling American bittern (Botaurus lentiginosus), in eggs of American coot (Fulica americana) and eared grebe (Podiceps caspicus), and in feathers of adult Canada geese (Branta canadensis). These species represent different levels on the food chain from primarily vegetation-eating species (geese, coot) to species that eat primarily fish (cormorant). A clear, positive relationship between level on the food chain and levels of heavy metals occurred only for mercury in feathers and eggs. Otherwise, eared grebes had the highest levels of all other metals in their eggs compared to the other species. No clear food chain pattern existed for feathers for the other metals. For eggs at Agassiz: 1) lead, selenium, and manganese levels were similar to those reported in the literature, 2) mercury levels were slightly higher for cormorants and night herons, 3) all species had higher chromium and cadmium levels than generally reported, and 4) eared grebes had significantly higher levels of cadmium than reported for any species from elsewhere. For adult feathers: 1) gulls had higher levels of lead than the other species, 2) cadmium levels were elevated in gulls and adult herons and cormorants, 3) mercury levels showed an increase with position on the food chain, 4) selenium and chromium levels of all birds at Agassiz were generally low and 5) manganese levels in adults were generally higher than in the literature for other species. Adults had significantly higher mercury levels than fledgling gulls, night herons, and bitterns.     

The importance of exogenous contamination on heavy metal levels in bird feathers. A field experiment with free-living great tits, Parus major

Feathers have been used extensively as non-destructive biomonitors for heavy metal pollution. Birds excrete heavy metals into growing feathers during moult. After feather formation, the feathers become isolated from the rest of the body, suggesting that the feathers contain information of circulating heavy metal concentrations in the blood at the time of their development. However, heavy metal levels may change due to exogenous contamination, resulting in higher concentrations in feathers that are exposed most to exogenous conditions. We studied the effect of exogenous contamination in free-living adult great tits (Parus major) by measuring--within the same individual--the concentrations of twelve heavy metals (Ag, Al, As, Cd, Co, Cu, Fe, Hg, Mn, Pb, Tl and Zn) in three outermost tail feathers that were exposed to exogenous contamination for different periods of time. In particular, for each individual heavy metal levels in the removed left outermost tail feather were compared with levels in the regrown left and the right outermost tail feather, that were both removed 40 days after removal of the original left feather. This study revealed that, with the exception of mercury, the concentration of all heavy metals was significantly different among the three outermost tail feathers. Our results suggest that concentrations of most heavy metals build up with increasing age of the feather, indicating that exogenous contamination may be an important source of heavy metals in feathers. However, we found no significant differences in Hg concentrations and we found only small differences in Zn concentrations among tail feathers. Consequently, the concentrations of zinc and mercury in feathers are probably primarily due to endogenous deposition.     

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

There is an abundance of field data for levels of metals from a range of places, but relatively few from the North Pacific Ocean and Bering Sea. In this paper we examine the levels of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in feathers from common eiders (Somateria mollissima), glaucous-winged gulls (Larus glaucescens), pigeon guillemots (Cepphus columba), tufted puffins (Fratercula cirrhata) and bald eagles (Haliaeetus leucocephalus) from the Aleutian Chain of Alaska. Our primary objective was to test the hypothesis that there are no trophic levels relationships for arsenic, cadmium, chromium, lead, manganese, mercury and selenium among these five species of birds breeding in the marine environment of the Aleutians. There were significant interspecific differences in all metal levels. As predicted bald eagles had the highest levels of arsenic, chromium, lead, and manganese, but puffins had the highest levels of selenium, and pigeon guillemot had higher levels of mercury than eagles (although the differences were not significant). Common eiders, at the lowest trophic level had the lowest levels of some metals (chromium, mercury and selenium). However, eiders had higher levels than all other species (except eagles) for arsenic, cadmium, lead, and manganese. Levels of lead were higher in breast than in wing feathers of bald eagles. Except for lead, there were no significant differences in metal levels in feathers of bald eagles nesting on Adak and Amchitka Island; lead was higher on Adak than Amchitka. Eagle chicks tended to have lower levels of manganese than older eagles.     

Heavy metal and selenium levels in feathers of herring gulls (Larus argentatus): Differences due to year,gender, and age at Captree,Long Island

The concentrations of heavy metals (mercury, lead, cadmium, chromium, manganese) and selenium in the feathers of herring gulls (Larus argentatus) from a nesting colony at Captree, Long Island, New York were examined from 1989 to 1993 to determine if there were differences from year to year, and between males and females, adult and young, and dead versus live gulls. Variation in metal levels in regression models was explained by age (all metals), year (all except manganese), and whether the feathers were from live or dead birds (all except lead and chromium). The feathers of adults had significantly higher levels of mercury, lead and manganese than those of young, but lower levels of selenium and cadmium than those of young. Levels in down and fledgling feathers were similar for lead, cadmium and selenium, but fledgling feathers had higher levels for mercury, chromium, and manganese. There were no gender differences in metal levels for adult feathers except for lead (females had higher levels). Levels of mercury and manganese were higher in feathers of live adults whereas levels of cadmium and selenium were higher in the feathers of dead adults.     

Mercury in Tree Swallow Food, Eggs, Bodies, and Feathers at Acadia National Park, Maine, and an EPA Superfund Site, Ayer, Massachusetts

We monitored nest boxes during 1997–1999 at Acadia National Park, Mt. Desert Island, ME and at an old-field site in Orono, ME to determine mercury (Hg) uptake in tree swallow (Tachycineta bicolor) eggs, tissues, and food boluses. Also, in 1998–1999 we monitored nest boxes at Grove Pond and Plow Shop Pond at a U.S. Environmental Protection Agency Superfund site in Ayer, MA. We recorded breeding success at all locations. On average among locations, total mercury (THg) biomagnified 2 to 4-fold from food to eggs and 9 to 18-fold from food to feathers. These are minimum values because the proportion of transferable methyl mercury (MeHg) of the THg in insects varies (i.e., 35%–95% of THg) in food boluses. THg was highest in food boluses at Aunt Betty Pond at Acadia, whereas THg in eggs was highest at the Superfund site. A few eggs from nests at each of these locations exceeded the threshold (i.e., 800–1,000 ng/g, wet wt.) of embryotoxicity established for Hg. Hatching success was 88.9% to 100% among locations, but five eggs failed to hatch from 4 of the 11 clutches in which an egg exceeded this threshold. MeHg in feathers was highest in tree swallows at Aunt Betty Pond and the concentration of THg in bodies was related to the concentration in feathers. Transfer of an average of 80%–92% of the Hg in bodies to feathers may have enhanced nestling survival. Residues of Hg in tissues of tree swallows in the Northeast seem higher than those of the Midwest.     

monitoring bioaccumulation of contaminants in the belted kingfisher (ceryle alcyon)

The belted kingfisher (Ceryle alcyon), acommon piscivore in the eastern United States, hasbecome a common endpoint in ecological riskassessments (ERA) because of their high consumptionof potentially contaminated aquatic prey. Whilebioaccumulation data and biosurveys may be used tosupport conclusions of ERAs for kingfishers, thereare currently no published data on contaminantconcentrations in kingfishers. Additionally,methods available for collecting biological samples(e.g., feathers, eggs, food debris, etc.) fromkingfisher burrows can be detrimental to thereproductive success of the birds. We present amethod for obtaining samples from burrows during orfollowing the nesting season. The method wasapplied to kingfisher burrows on the Oak RidgeReservation (ORR) in eastern Tennessee. Feathers,eggshells, and nestlings were collected from burrows and analyzed. In addition, carcasses ofthree adult kingfishers found dead on the ORR wereanalyzed. Metals and radionuclides were accumulatedby both juvenile and adult birds. Body burdens ofcadmium, lead, and cesium-137 in adult birds were belowlevels associated with toxicity. Concentrations of selenium and mercury were observed at potentiallytoxic levels. Contaminants in eggshells andnestling feathers indicate exposure, however, thereis insufficient information to evaluate thetoxicological significance of this contamination.National Laboratory Oak Ridge National Laboratory is managed for the U.S. Department of Energy by Lockheed Martin Energy Research Corp. under contract DE-AC05-96OR22464     

The use of bird feathers for indicating heavy metal pollution

Feather material has been investigated as suitable indicating tissue for heavy metal pollution. At least three different routes are described through which trace metal content in the feathers can increase: internal deposition during growth, contamination by the bird's secretion and outside contamination.As mercury is only deposited during feather growth, the feather burden reflects the internal contamination of the bird. Internal deposition of zinc appears to be well regulated in the shaft but concentrations differ widely in the vanes. No external contamination of the vanes could be demonstrated, so these levels reflect contamination from inside. Selenium and lead contamination can be deposited by the birds secretion. When the time elapsed after feather formation is accounted for, the feather can give indirectly an indication of the birds exposure to these elements.     

Heavy metal concentrations in feathers of common loons (Gavia immer) in the Northeastern United States and age differences in mercury levels

Feathers serve as a useful, non-destructive approach for biomonitoring some aspects of environmental quality. Birds can eliminate over 90% of their body burden of mercury by sequestration in growing feathers, and they molt their feathers at least annually. Thus mercury concentrations should not vary in avian feathers as a function of age. We tested the null hypothesis that there are no age differences in the concentrations of mercury, lead, cadmium, selenium, copper, chromium and manganese in the feathers of immature and adult common loons Gavia immer from the Northeastern United States where the species is declining. Adults had significantly higher mean levels of mercury (20245 ppb) than immature loons (9677 ppb), but there were no age-related differences for other elements. Even with the small number of immatures, females had significantly higher levels of mercury than males, although the gender difference was not significant for adults.     

Little Egrets (Egretta Garzetta) and Trace-Metal Contamination in Wetlands of China

The rapidly developing Asian countries may face threatening environmental contamination, that however remains largely unassessed. We studied persistent trace elements in three wetlands, Poyang Lake, relatively unpolluted, and Tai Lake, and Pearl River Delta, selected as hotspots of pollution in Central China. We adopted as indicator the Little Egret, a widespread colonial waterbird, and during 1999 and 2000 we collected and analysed the same samples as for a parallel study we conducted in Pakistan, e.g. eggs, body feathers of chicks, prey spontaneously regurgitated by the chicks, and sediments at the areas most used by foraging egrets. The levels of trace-metals at our three study areas were similar, or within the range, of those found in the few other studies for East Asia, with few exceptions. The concentrations of the various elements were below the threshold that may affect the survival or reproduction of the birds, and even the highest concentrations relative to background, i.e. Se in eggs, and Hg in feathers at Pearl Delta, do not pose toxic hazards. In sediments, the levels of trace elements were lower than the critical levels assumed for contaminated soil, except for alarming high levels of As at Poyang. These results do not confirm our expectation, that Poyang was relatively uncontaminated, while Tai and Pearl were polluted. Although trace metal concentration differed significantly among the three study areas, these differences were minor and were not consistent among elements and samples. The bioaccumulation ratios from sediments through prey, feather and egg, were consistent with our previous findings for Pakistan. Only Hg exhibited high bioaccumulation, while Se and Zn had low accumulation, and the other elements no accumulation. This reasserts that feathers of predators such as egrets, may be more sensitive indicators of environmental contamination for the elements subject to bioaccumulation, whereas the sediments or the organisms low in the food chain are better indicators for the other elements.     

Heavy Metals and Selenium in Herring Gulls (LARUS ARGENTATUS) NESTING IN COLONIES FROM EASTERN LONG ISLAND TO VIRGINIA

With increasing interest in assessing the health or well-being ofcommunities and ecosystems, birds are being used asbioindicators. Coloniallynesting species breed mainly in coastal areas that are alsopreferred for humandevelopment, exposing the birds to various pollutants. Inthis paper concentrations of heavy metal and selenium in the feathers ofHerring Gulls(Larus argentatus) nesting in several colonies fromMassachusetts toDelaware are reported. There were significant differencesamong colonies forall metals, with metal concentrations being two to nearly fivetimes higher atsome colonies than others. Selenium showed the leastdifference, and cadmium showed the greatest difference among sites. Concentrations of lead werehighest at Pralls Island; mercury was highest at Shinnecock,Huckleberry andHarvey, and manganese was highest at Captree.     

Cadmium and lead in common terns (Aves: Sterna hirundo): Relationship between levels in parents and eggs

We analyzed cadmium and lead levels in feathers of mated pairs of common terns (Sterna hirundo) and in their eggs to determine if metal levels in eggs correlated with female levels, and whether there were intrapair and intermetal correlations. Eggs had significantly lower lead levels (89 ng g^-1) and cadmium levels (4.0 ng g^-1) than adult feathers (500 and 50 ng g^-1 respectively). Adult females had higher metal levels than males. Cadmium and lead levels were correlated across families for females, males and eggs. Lead, but not cadmium, levels were correlated in females and their eggs.     

Biogenic and toxic elements in feathers, eggs, and excreta of Gentoo penguin (Pygoscelis papua ellsworthii) in the Antarctic

Feathers, eggs, and excreta of Gentoo penguin (Pygoscelis papua ellsworthii), adults, from Livingston Island (South Shetlands), chosen as bioindicators, were used to test the quality of the Antarctic environment. Sex was not examined. The bioaccumulations of toxic trace elements (Cd, Pb, Al, and As), essential trace elements (Fe, Cu, Zn, Mn, Cr, V, Ni, and Sr), and major essential elements (Na, K, Mg, Ca, P, and S) were established. For the first time data about the element contents in Gentoo eggs is provided. Two hypotheses were tested: (1) there are differences in the metal levels among eggs and feathers; and (2) the element concentrations are highest in the excreta. The hypotheses were confirmed at 0.01-0.05 confidence levels. The concentrations of almost all trace elements were significantly higher in the feathers compared to those in the eggs. The following values of the concentrations ratio Fe/Zn were obtained: in the embryo, Fe/Zn = 1.5, and in the feathers, Fe/Zn = 0.5. The concentration of Pb in the embryo and excreta was below 0.4 μg/g, and Cd and As in eggs were below 0.05 and 0.3 μg/g, respectively. This indicates that there is no toxic risk for penguin offspring. Arsenic could be considered as a potential pollutant for Antarctic soil due to its relative high concentration in excreta, 5.13 μg/g. The present data (year 2007) were compared to the data for years 2002 and 2003. No trend of toxic element contamination was established. The concentrations of Pb, Cd, and As in representatives from the top of the food chain in the Antarctic (the present study) and Arctic (literature data) were compared. The data supports the hypothesis that there is an abnormality in cadmium levels in polar marine areas. Regarding Pb, the South Shetlands displayed 3-fold lower level compared to the Aleutians.     

Metals in feathers of brown noddy (Anous stolidus): Evidence for bioaccumulation or exposure levels?

Levels of environmental pollution are generally assumed to be greater in nearshore and estuarine habitats compared to the open ocean. This difference presumably derives from high inputs from industrial and agricultural sources entering estuaries and bays from rivers and as direct runoff. This suggests that levels of heavy metals should be higher in birds that obtain their food resources from nearshore habitats rather than the open ocean far from land. I compared the levels of lead, cadmium, mercury and selenium in feathers of young and adult brown noddies (Anous stolidus) along the coast of Oahu, Hawaii. Prior to fledging, young noddies obtain all their food resources from their parents that bring back fish and squid from a few km offshore, whereas adults spend much of the year outside the breeding season on the open ocean, where they obtain most of the metals that accumulate in their feathers. For all metals, the young noddies had lower levels than adults. These data do not support the hypothesis that heavy metal pollution is greater nearshore than on the open ocean, but further investigation is needed to distinguish simple biaccumulation with age from differential exposure by habitat, and contamination from the birds own secretions during preening and from the outside.     

Heavy Metals in the Eggs and Muscle of Horseshoe Crabs (Limulus Polyphemus) from Delaware Bay

Lead, mercury, cadmium, chromium and manganese concentrations were measured in the eggs of horseshoe crabs (Limulus polyphemus) from 1993, 1994 and 1995; and from chelicera muscle in 1995 from Delaware Bay. Metal concentrations in the eggs represent levels derived from females. In eggs, mercury levels were below 100 ppb or were non-dectable; cadmium levels were generally low in 1993 and 1995 but were relatively higher in 1994; lead levels in eggs decreased from 558 ppb in 1993 to 87 ppm in 1995; selenium increased from 1993 to 1995; chromium decreased from 1993 to 1995; and manganese generally decreased. Leg muscles had significantly lower levels of all metals than eggs, except for mercury.     

Interspecific and Locational Differences in Heavy Metal Levels in Four Species of Birds Near Sydney, Australia

We examined the levels of cadmium, chromium, lead, manganese, mercury, and selenium in four species of birds near Sydney, New South Wales, Australia in January, 1996. Molted contour feathers were collected from silver gull, Larus novaehollandiae (Royal National Park and downtown Sydney), sulphur-crested cockatoo, Cacatua sulphurea (Blue Mountains, Royal National Park, and Sydney), Australian white ibis, Threskiornis molucca (Sydney), and rock dove Columba livia (Royal National Park and Sydney). We tested the null hypothesis that there were no species or locational differences in metal levels. There were significant species differences in all metals, with rock doves having the highest levels of cadmium, chromium, lead, and manganese, and silver gulls having the highest levels of mercury and selenium. Metal levels were generally low in cockatoos, and were lowest in those from the Royal National Park. For silver gulls, cadmium, lead, and chromium levels were highest at Sydney, and there were no locational differences in manganese, mercury, and selenium levels. For rock doves, cadmium, chromium and manganese were higher in Sydney, and there were no locational differences in lead, mercury, and selenium. Overall, cadmium and chromium levels were significantly higher in Sydney than in the Royal National Park for all species, and there were no locational differences in mercury levels. Although the levels of most metals in feathers from these Australian birds were within the ranges reported worldwide, lead levels in ibises and rock doves were among the highest reported worldwide, suggesting a cause for concern.     

Locational differences in metal concentrations in feathers of Australasian gannet (Morus serrator) in New Zealand

Levels of lead, cadmium, mercury, selenium, manganese and chromium were examined in breast feathers of Australasian Gannets (Morus serrator) from New Zealand waters, where they breed on coastal rocky stacks, islands, and occasionally coastal headlands. There were significant differences in the concentrations of all metals except mercury, with gannets from Ninety Mile Beach having significantly lower levels of all metals than those from the other beaches. Ninety Mile Beach is on the northern tip of the North Island, away from urbanization and industrialization, whereas the other beaches are closer to Auckland, the largest city in New Zealand. The levels of most metals were similar or lower than those reported for feathers from elsewhere around the world. Mercury, however, was at the high end, being exceeded only by raptors and gulls from industrialized countries. Several metal levels were highly correlated, indicating that gannets were usually exposed to several metals at once.     

Monitoring for Lead Pollution using Feathers of Feral Pigeons (Columba livia) from Korea

We investigated lead exposure conditions using unwashed feathers of feral pigeons as a monitor for lead pollution from rural, central urban, and four industrial complex areas in Korea with different ambient lead concentrations. Overall, the lead levels in the feathers increased when the atmospheric lead levels increased, so that the lead levels in the feathers from urban and industrial areas were two to four times greater than those in the rural area. However, there are no significant differences in the liver lead concentrations between rural and the other areas, suggesting that the lead originated from ingestion are not differences in locations. A positive correlation was found between the concentration of lead in livers and feathers from rural, indicating that the feather lead concentrations in this area seem to mainly reflect the internal tissue lead through the metabolic process. However, there are no significant correlations in the other areas, and we observed a relatively higher lead accumulation ratio of feathers to livers. It, therefore, indicates that external contamination onto the feather surface may be an important source for lead levels in feathers rather than transfer from internal tissue lead.     

Particle-phase Polycyclic Aromatic Hydrocarbon Emissions from Non-catalysed, In-use Four-stroke Scooters

Metals and radionuclide levels in marine birds of the Aleutians are of interest because they are part of subsistence diets of the Aleut people, and can also serve as indicators of marine pollution. We examined geographic and species-specific variations in concentrations of radionuclides in birds and their eggs from Amchitka, the site of underground nuclear tests from 1965 to 1971, and Kiska Islands (a reference site) in the Aleutians, and the levels of lead, mercury and cadmium in eggs. In 2004 we collected common eiders (Somateria mollissima), tufted puffins (Fratercula cirrhata), pigeon guillemot (Cepphus columba) and glaucous-winged gulls (Larus glaucescens) from Amchitka and Kiska, and eggs from eiders and gulls from the two island. We also collected one runt bald eagle (Haliaeetus leucocephalus) chick from both Amchitka and Kiska Islands. For most species, the levels of radionuclide isotopes were below the minimum detectable activity levels (MDA). Out of 74 cesium-137 analyses, only one composite (gulls) was above the MDA, and out of 14 composites tested for plutonium (Pu-239, 240), only one exceeded the MDA (a guillemots). Three composites out of 14 tested had detectable uranium-238. In all cases, the levels were low and close to the MDAs, and were below those reported for other seabirds. There were significant interspecific differences in metal levels in eggs: gulls had significantly higher levels of cadmium and mercury than the eiders, and eiders had higher levels of lead than gulls. There were few significant differences as a function of island, but eiders had significantly higher levels of cadmium in eggs from Kiska, and gulls had significantly higher levels of mercury on Kiska. The levels of cadmium and mercury in eggs of eiders and gulls from this study were above the median for cadmium and mercury from studies in the literature. The levels of mercury in eggs are within the range known to affect avian predators, but seabirds seem less vulnerable to mercury than other birds. However, the levels of mercury are within the action levels for humans, suggesting some cause for concern if subsistence Aleuts eat a large quantity of eggs.