Trace element distribution in growing feathers: Additional excretion in feather sheaths

The use of feathers is a non-invasive and repeatable method for biomonitoring trace element levels in birds and their ecosystems. Trace element levels were examined in different parts of growing flight feathers from young common terns (Sterna hirundo) to determine distribution of heavy metals and selenium, potential bias from using partially grown feathers, and whether additional heavy metals and selenium are excreted in feather sheaths that are sloughed before feathers are usually sampled. Lead and mercury levels were significantly higher in the distal fully formed portion of the growing feather (with no residual blood supply) compared to the proximal, growing portion of the feather with a residual blood supply, but no significant differences were evident for cadmium and selenium. These results suggest that using partially grown feathers underestimates the amount of lead and mercury in fully formed feathers and that higher levels of lead and mercury are sequestered in feathers than are present in the blood at any one time. Significantly higher concentrations of lead and cadmium, and significantly lower levels of mercury were in the sheath compared to the whole feather blade. These data suggest that birds excrete more lead and cadmium during molt than previously thought.     

Examination of mercury concentration in the feathers of 18 species of birds in southwest Iran

This paper presents the levels of mercury (Hg) in tail feathers from different species of birds, in southwest Iran (Khuzestan to Persian Gulf). Between April and October 2005, we collected tail feathers from 77 birds belonging to 18 species, mostly raptor birds. The birds were collected for the Museum Natural History, Faculty of Natural Resources and Marine Sciences of Tarbiat Modares University. Hg concentrations were evaluated in relation to taxonomic affiliation and trophic level. Feather Hg concentrations ranged from 0.09 to 2.01 mg/kg dry wt. We found a significant difference in feather Hg concentrations across taxonomic groups (p<0.001) with highest concentrations in common kestrel and saker falcon (Falconidae) (1.87 mg/kg) followed by greater spotted eagle, sparrowhawk, goshawk, griffon vulture, buzzards, marsh harrier (Accipiteridae) and owls (Strigidae). Blue-cheeked bee-eater (Meropidae) had intermediate values, followed by European roller (Coraciidae), and lapwing (Charadiidae), whereas black francolin, see-see patridge and chukar (Phasianidae) (0.18 mg/kg) contained the least amount of Hg. There was a significant difference in feather Hg concentrations in relation to trophic levels, at confidence level of 99% (p<0.001). There was an increased pattern in the amount of mercury from herbivorous birds up to vertebrate predators, so that the amount of mercury in vertebrate predators (1.30 mg/kg) was more than 1.5 times as much of the invertebrate predators (0.7 mg/kg) and more than 6 times as much of the herbivorous birds (0.18 mg/kg). We also measured Hg levels in secondary feathers of raptor birds. Paired samples t-test showed that the concentrations of mercury were significantly higher (p<0.001) in the tail feathers (1.2mg/kg) than secondary (0.71 mg/kg). However, Hg levels are below the range found by other authors to cause behavioral change or reduce reproduction (5mg/kg). It seems that exposure of some birds with mercury for a long time causes their high concentration of mercury.     

Lead accumulation in feathers of nestling black-crowned night herons (Nycticorax nycticorax) experimentally treated in the field

Although lead can attain high concentrations in feathers, interpretation of the biological significance of this phenomenon is difficult. As part of an effort to develop and validate noninvasive methods to monitor contaminant exposure in free-ranging birds, lead uptake by feathers of nestling black-crowned night herons (Nycticorax nycticorax) was evaluated in a controlled exposure study. Four- to 6-d-old heron nestlings (one/nest) at Chincoteague Bay, Virginia (USA), received a single intraperitoneal injection of dosing vehicle (control, n = 7) or a dose of lead nitrate in water (0.01, 0.05, or 0.25 mg Pb/g body wt of nestling; n = 6 or 7/dose) chosen to yield feather lead concentrations found at low- to moderately polluted sites. Nestlings were euthanized at 15 d of age. Lead accumulation in feathers was associated with concentrations in bone, kidney, and liver (r = 0.32-0.74, p < 0.02) but exhibited only modest dose dependence. Blood delta-aminolevulinic acid dehydratase activity was inhibited by lead, although effects on other biochemical endpoints were marginal. Tarsus growth rate was inversely related to feather lead concentration. Culmen growth rate was depressed in nestlings treated with the highest dose of lead but not correlated with feather lead concentration. These findings provide evidence that feathers of nestling herons are a sensitive indicator of lead exposure and have potential application for the extrapolation of lead concentrations in other tissues and the estimation of environmental lead exposure in birds.     

Mercury concentrations in blood and feathers of prebreeding Forster's terns in relation to space use of San Francisco Bay, California, USA, habitats

We examined mercury concentrations and space use of prebreeding Forster's terns (Sterna forsteri) in San Francisco Bay, California, USA, to assess factors influencing mercury levels in piscivorous birds. In 2005 and 2006, we collected blood and feathers from 122 Forster's terns and radio-marked and tracked 72 terns to determine locations of dietary mercury uptake. Capture site and capture date were the most important factors explaining variation in blood mercury concentrations (geometric mean +/- standard error: 1.09+/-0.89 microg/g wet wt), followed by sex and year. Accordingly, radiotelemetry data revealed that Forster's terns generally remained near their site of capture and foraged in nearby salt ponds, managed and tidal marshes, and tidal flats. In contrast, capture site and capture date were not important factors explaining variation in feather mercury concentrations, probably because feathers were grown on their wintering grounds several months prior to our sampling. Instead, sex and year were the most important factors explaining mercury concentrations in breast feathers (9.57+/-8.23 microg/g fresh wt), and sex was the most important factor for head feathers (6.94+/-7.04 microg/g fresh wt). Overall, 13 and 22% of prebreeding Forster's terns were estimated to be at high risk for deleterious effects due to mercury concentrations in blood (>3.0 microg/g wet wt) and feathers (>20.0 microg/g fresh wt), respectively. Breeding terns are likely to be even more at risk because blood mercury concentrations more than tripled during the 45-d prebreeding time period. These data illustrate the importance of space use and tissue type in interpreting mercury concentrations in birds.     

Sedentary nestlings of Wood Stork as monitors of mercury contamination in the gold mining region of the Brazilian Pantanal

Sedentary organisms that are at top trophic levels allow inference about the level of local mercury contamination. We evaluated mercury contamination in feather tissue of nestling Wood Storks (Mycteria americana), sampled in different parts of the Brazilian Pantanal that were variably polluted by mercury releases from gold mining activities. Levels of mercury in feathers sampled in seven breeding colonies were determined by atomic absorption spectroscopy, and the mean value of mercury concentration was 0.557 μg/g, dry weight (n=124), range 0.024–4.423 μg/g. From this total sample, 21 feathers that represent 30% of nestlings collected in Porto da Fazenda and Tucum colonies, in the northern region, ranged from 1.0 to 4.43 μg/g, dry weight (median value=1.87 μg/g). We found significant differences among regions (H=57.342; p=0<0.05). Results suggest that permanently flooded areas, or along mainstream rivers are more contaminated by mercury than dry areas, regardless of the distance from the gold mining center, which is located in the northern Pantanal. Highest values found in nestlings feathers were similar to those found in feathers of adult birds and in tissues of adult mammals that are less sedentary and were captured in the same region of Pantanal. These findings indicate that mercury released has been biomagnified and it is present in high concentrations in tissues of top consumers. We suggest a program to monitor mercury availability in this ecosystem using sedentary life forms of top predators like Wood Storks or other piscivorous birds.     

Sensitivity of nestling and adult starlings to dicrotophos, an organophosphate pesticide

The 24-hr median lethal dose (LD50) of dicrotophos (3-hydroxy-N,N-dimethyl-cis-crotonamide dimethyl phosphate) for free-living 5-day-old nestling European starlings (Sturnus vulgaris, LD50 = 4.92 mg/kg body wt) was about one-half that obtained for free-living 15-day-old nestlings (9.59 mg/kg) and captive adult males (8.37 mg/kg) and females (8.47 mg/kg). Nestlings and adults with low pretreatment body weights appeared to be more vulnerable to organophosphate (OP) exposure. Brain cholinesterase (ChE) activity was severely depressed in all birds that died (74-94%); the degree of inhibition did not vary with age or sex. Inhibition of brain ChE in 5-day-old nestlings alive 24 hr post dose (mean = 28-43%) was lower than that of 15-day-old (mean = 55-68%) and adult (mean = 55-77%) survivors. Body weights of OP-dosed birds that died were depressed an average of 20 to 46% in 5-day-olds, 7 to 20% in 15-day-olds, and 0 to 10% in adults; weight losses varied inversely with age and dosage, and directly with time to death. Average weight losses in 5- and 15-day-old survivors (mean less than or equal to 31 and 26%, respectively) varied directly with dose and exceeded comparable values for adults (mean = 3-15%). Results suggest that (1) young nestling songbirds may be nearly twice as sensitive as adults to OPs, (2) growth of nestlings may be severely depressed following OP exposure, and (3) recovery of brain ChE activity following exposure to ChE inhibitors may be more rapid in nestlings than adults.     

A historical record of mercury contamination in Southern Florida (USA) as inferred from avian feather tissue

During the late 1980s, the upper trophic-level biota of the Everglades (FL, USA) was recognized as being highly contaminated with mercury (Hg). However, the timing and pattern of that increase is poorly known, and no information is available about mercury contamination in Everglades wildlife prior to 1974. We measured methylmercury concentrations in feathers of white ibises (n = 33), great egrets (n = 7), anhingas (n = 21), and great blue herons (n = 12) from museum specimens collected from 1910 through 1980 and combined them with more recent feather samples collected from live birds (1985-2000, n = 98, 37, 49, and 7, respectively). We found no evidence of contamination of museum samples with inorganic mercuric preservatives (0.01-0.28% of total Hg in feathers). All species showed relatively low concentrations of mercury through the 1970s (<5 microl/L dry wt for anhingas, ibises, and egrets, <10 microl/L for herons). Samples from all species taken during the 1990s showed a large and significant increase (4-5X) in MeHg concentration. This evidence suggests that most of the increase in Hg deposition during the 20th century in south Florida occurred during the last two to three decades, which is consistent with information about local source deposition. Contamination levels prior to the 1970s appear to have been associated with normal reproduction in these birds, suggesting partial evidence for a threshold of reproductive impairment.     

A multispecies-monitoring study about bioaccumulation of mercury in Iranian birds (Khuzestan to Persian Gulf): Effect of taxonomic affiliation and trophic level

In the present study, the first baseline concentration of mercury (Hg) in different species of Iranian birds was investigated. From April to October 2005, the tail feathers of 100 birds belonging to 27 species (14 families) from different places in southwest Iran (Khuzestan to Persian Gulf) were collected. The Hg levels were evaluated in relation to taxonomic affiliation and trophic level (type of food). The results showed that the Hg levels in the feathers were between 0.07 and 4.71 mg/kg dry weight (dw), and there was a significant effect of taxonomic groups in relation to Hg concentration (p<0.001). The highest mercury concentrations were in Laridae and Ciconidae. Alcedinidae had intermediate values, whereas Upupidae, Glareolidae, Scolopacidae, Turdidae, Ardeidae, Anatidae were in subsequent orders; and the lowest concentrations of Hg were in Rallidae, Cuculidae, Pycnonotidae, Corvidae and Columbidae. The results indicated a significant difference between the trophic levels (p<0.001). Fish predators had the highest level of Hg (3.07 mg/kg). Invertebrate predators and herbivorous birds had the lowest concentration of Hg (0.84 and 0.64 mg/kg, respectively), whereas crab and fish predators and omnivorous birds had moderate values (1.73 and 1.70 mg/kg, respectively). In the present study, the concentration of Hg was significantly higher in tail feathers than in primary and secondary (p<0.001). A significant positive correlation among Hg concentration of feather types was observed (r>0.96). The results obtained in this study indicated that among 100 birds tested, 6% of them had Hg concentrations greater than 5 mg/kg in feather (adverse level).     

The use of bird feathers for the monitoring of cadmium pollution

The cadmium contamination mechanism in bird feathers was investigated using starlings fed with diets containing 10 and 50 ppm Cd for five months. The experiment started about two months before the beginning of the annual complete feather molt and lasted until most of the birds completed the molt of the primaries. Concentrations of Cd in liver, kidney, and uropygial gland were highly correlated, but uropygial gland concentration was about 100 times lower. Cadmium was found both in old and new feathers, in a dose-related manner. Old. feathers showed higher metal concentrations than new ones and primaries higher than secondaries. Feather Cd concentration correlated with Cd concentration in liver, kidney, and the uropygial gland. The use of bird feathers are, therefore, a reliable method for monitoring cadmium pollution, but differences between feather type and age must be considered to correctly interpret data collected in the field.     

Using feathers to assess risk of mercury and selenium to bald eagle reproduction in the Great Lakes region

Mercury (Hg) and selenium (Se) concentrations were determined in feathers of nestling and adult bald eagles (Haliaeetus leucocephalus) in the Great Lakes region, 1985–1989. Relationships between concentrations and two measures of reproduction, productivity and nesting success, were examined. Hg and Se were detected in all feathers analyzed. A maximum concentration of 66 mg/kg Hg was found in adult feathers in the upper peninsula of Michigan. The geometric means of Hg in adult feathers for sample areas were: interior lower peninsula of Michigan, 21 mg/kg; interior upper peninsula of Michigan, 21 mg/kg; Lake Superior, 22 mg/kg; Lakes Michigan and Huron, 20 mg/kg; and Lake Erie, 13 mg/kg. The geometric means of Hg in nestling feathers for sample areas were: interior lower peninsula of Michigan, 8.8 mg/kg; interior upper peninsula of Michigan, 8.1 mg/kg; Lake Superior, 8.7 mg/kg; Lakes Michigan and Huron, 8.0 mg/kg; Lake Erie, 3.7 mg/kg; and Voyageurs National Park, 20 mg/kg. Se concentrations were not significantly different across regions or between adult and nestling feathers, and Se concentrations ranged from 0.8 to 3.2 mg/kg.No significant relationships between adult or nestling feather concentrations and either measure of reproduction, productivity or nesting success, was found for either Hg or Se. It was concluded that neither Hg nor Se concentrations are currently affecting bald eagle reproduction in the Great Lakes region.     

Cadmium, lead, and mercury levels in feathers of small passerine birds: noninvasive sampling strategy

Bird feathers have been widely used as a nondestructive biological material for monitoring heavy metals. Sources of metals taken up by feathers include diet (metals are incorporated during feather formation), preening, and direct contact with metals in water, air, dust, and plants. In the literature, data regarding the origin of trace elements in feathers are not univocal. Only in the vast literature concerning mercury (as methyl mercury) has endogenous origin been determined. In the present study, we investigate cadmium, lead, and mercury levels in feathers of prey of Falco eleonorae in relation to the ecological characteristics (molt, habitat, and contamination by soil) of the different species. Cluster analysis identified two main groups of species. Differences and correlations within and between groups identified by cluster analysis were then checked by nonparametric statistical analysis. The results showed that mercury levels had a pattern significantly different from those of cadmium and lead, which in turn showed a significant positive correlation, suggesting different origins. Nests of F. eleonorae proved to be a good source for feathers of small trans-Saharan passerines collected by a noninvasive method. They provided abundant feathers of the various species in a relatively small area--in this case, the falcon colony on the Isle of San Pietro, Sardinia, Italy.     

Mercury Accumulation and Biomagnification in Ospreys (Pandion haliaetus) in the James Bay and Hudson Bay Regions of Québec

Mercury exposure was examined in adults and nestlings of ospreys (Pandion haliaetus) from lakes, rivers, and hydroelectric reservoirs in northern Québec between 1989 and 1991 by assessing the amount of mercury transferred from fish to ospreys, which are voracious fish-eaters. The high mercury concentrations detected in adult feathers and tissues (feathers, blood, liver, kidneys, muscles, brain) of nestlings indicate an increase in mercury availability at recently constructed hydroelectric reservoirs (10–12 years for the La Grande-2 Reservoir). With mean total mercury levels of 37.3 mg/kg and 1.9 mg/kg in feathers (dry weight) and in blood (wet weight), respectively, contamination rates were, in both tissues, five times higher for chicks born near the La Grande Reservoirs (western sector) than in those reared in natural habitats. Furthermore, the mean quantity of total mercury in 40-day-old chicks reared near a reservoir was 10.5 mg, compared with to 1.6 mg for those reared in a natural environment. Modeling of mercury transfer from fish to osprey nestlings showed that the mercury level in chicks' blood provides a good estimate of mercury concentrations in ingested food. In addition, the relationship between mercury concentrations in the blood and that in feathers indicates that substantial biomagnification of mercury occurs from the ingested dose to the feathers. The intensity of this biomagnification varies with the age of the chicks and reaches a maximum value as the flight feathers start to form (at 20–25 days of age) declining thereafter until the bird is 45 days old and growth of those feathers is complete. Nevertheless, the mean number of young fledged on reservoirs where mercury exposure is greatest (>40 mg/kg of Hg in chicks' feathers) did not differ (1.6 ± 0.7) from that observed elsewhere in built-up environments (1.9 ± 0.7) or in natural habitats (2.0 ± 0.7) (H = 4.39; p = 0.11). Storage of mercury in growing feathers (86% of all mercury in osprey) prevents accumulation in living tissues, thereby protecting the chick from related toxic effects. However, toxicological problems may arise after fledging. In particular, attention should be paid to postfledging survival before concluding that mercury exposure is insufficiently high in Osprey young reared at reservoirs. Received: 18 April 1997/Accepted: 3 January 1998     

Lead, mercury, cadmium, chromium, and arsenic levels in eggs, feathers, and tissues of Canada geese of the New Jersey Meadowlands

The New Jersey Meadowlands are located within the heavily urbanized New York/New Jersey Harbor Estuary and have been subject to contamination due to effluent and runoff from industry, traffic, and homes along the Hackensack River and nearby waterways. These extensive wetlands, though heavily impacted by development and pollution, support a wide array of bird and other wildlife species. Persistent contaminants may pose threats to birds in these habitats, affecting reproduction, egg hatchability, nestling survival, and neurobehavioral development. Metals of concern in the Meadowlands include arsenic, cadmium, chromium, lead, and mercury. These metals were analyzed in eggs, feathers, muscle, and liver of Canada geese (Branta canadensis) breeding in four wetland sites. We sampled geese collected during control culling (n=26) and collected eggs from goose nests (n=34). Levels of arsenic were below the minimum quantification level (MQL) in most samples, and cadmium and mercury were low in all tissues sampled. Chromium levels were high in feather samples. Mercury levels in eggs of Canada geese, an almost exclusively herbivorous species, were lower (mean ±SE 4.29±0.30 μg/g wet weight) than in eggs of omnivorous mallards (Anas platyrhynchos), and insectivorous red-winged blackbirds (Agelaius phoeniceus) and marsh wrens (Cistothorus palustris) from the Meadowlands, consistent with trophic level differences. However, lead levels were higher in the goose eggs (161±36.7 ng/g) than in the other species. Geese also had higher levels of lead in feathers (1910±386 ng/g) than those seen in Meadowlands passerines. By contrast, muscle and liver lead levels were within the range reported in waterfowl elsewhere, possibly a reflection of metal sequestration in eggs and feathers. Elevated lead levels may be the result of sediment ingestion or ingestion of lead shot and sinkers. Finally, lead levels in goose liver (249±44.7 ng/g) and eggs (161±36.7 ng/g) may pose a risk if consumed frequently by humans. Mill Creek, the site with the most documented prior contamination, had significantly elevated cadmium, chromium, mercury, and lead in goose tissues.     

Metals in albatross feathers from midway atoll: influence of species, age, and nest location

Female birds sequester some heavy metals in their eggs, which are then transferred to the developing embryo. Semiprecocial birds such as albatrosses are fully covered with down at hatching, but are dependent on their parents for food for many weeks. At hatching, levels of metals in the chick's down represent exposure from the female via egg, while levels in fully formed feathers at fledgling, several months later, represent mainly exposure from food provided by their parents. In this paper we examine the concentrations of "metals" (heavy metals, mercury, lead, cadmium, chromium, manganese, tin; and metalloids, arsenic and selenium), in the down and contour (body) feathers of half-grown young albatrosses, and contour feathers of one of their parents. We collected feathers from Laysan Diomedea immutabilis and black-footed Diomedea nigripes albatrosses from Midway Atoll in the central Pacific Ocean. We test the null hypotheses that there is no difference in metal levels as a function of species, age, feather type, and location on the island. Using linear regression we found significant models accounting for the variation in the concentrations of mercury, lead, cadmium, selenium, chromium, and manganese (but not arsenic or tin) as a function of feather type (all metals), collection location (all metals but lead), species (selenium only), and interactions between these factors. Most metals (except mercury, arsenic, and tin) were significantly higher in down than in the contour feathers of either chicks or adults. Comparing the two species, black-footed albatross chicks had higher levels of most elements (except arsenic) in their feathers and/or down. Black-footed adults had significantly higher levels of mercury and selenium. We also collected down and feathers from Laysan albatross chicks whose nests were close to buildings, including buildings with flaking lead paint and those that had been lead-abated. Lead levels in the down and feathers of chicks close to nonabated buildings were 10 times higher than for chicks from other locations. Conversely, levels of cadmium and tin were lower near the buildings. Near lead-abated buildings, lead levels decreased as a function of distance, indicating residual contamination on the soil. Our results indicate that black-footed albatross adults and chicks generally have higher levels of heavy metals in their feathers than Laysans. Chicks of both species have higher levels in their down than in their contour feathers, indicating potentially higher exposure during the early chick phase.     

Effects of Mercury on Health and First-Year Survival of Free-Ranging Great Egrets (Ardea albus) from Southern Florida

The objectives of this study were to determine whether elevated mercury (Hg) concentrations have a negative impact on the health and survival of nestling and juvenile free-ranging great egrets (Ardea albus) from southern Florida. During 1994, when health and survival was monitored in a cohort of young birds with naturally variable concentrations of Hg, packed cell volume was positively correlated with blood Hg concentrations, and high Hg concentration in blood was not related to the probability of surviving during the first 10.5 months of life. During 1995, 70 first-hatched great egret chicks were included in a Hg field-dosing experiment to compare the effects of elevated Hg on health and survival. Birds were dosed while in the nest orally every 2.5 days for 15 days with 0.5 mg of methyl mercury chloride (MeHgCl) for an estimated intake of 1.54 mg MeHgCl/kg food intake. These birds were compared with controls, which received an estimated 0.41 mg MeHgCl/kg food. No differences were observed in health parameters or in the probability of surviving during the first 8 months of age between egrets that were dosed with Hg and those that were not. A likely explanation for the lack of any effects on health and survival between both groups could be that chicks at this age were eliminating most of the dietary Hg through the production of new feathers. Received: 10 November 1998/Accepted: 8 April 1999     

Mercury Contamination in Idaho Bald Eagles, <Emphasis Type="Italic">Haliaeetus leucocephalus</Emphasis>

Because mercury contamination is potentially threatening to bald eagle (Haliaeetus leucocephalus) populations, we collected molted feathers at nests to determine the level of contamination in bald eagles in the state of Idaho, USA. Eagle feathers contained measurable amounts of cadmium (Cd), chromium (Cr), selenium (Se), lead (Pb), as well as mercury (Hg). Cadmium, Cr, Se, and Pb levels averaged 0.17, 4.68, 2.02, and 1.29 mg/kg dry weight, respectively, and were at or below concentrations indicated as causing reproductive failure in bald eagles. Mercury contamination was found to be the highest averaging 18.74 mg/kg dry weight. Although a concentration of only 7.5 mg/kg dry weight Hg in bird feathers can cause reduced productivity and even sterility, all of the eagles we sampled bred successfully and the population of bald eagles continues to grow annually throughout the state.     

Changes of Mercury Contamination in Red-Crowned Cranes, Grus japonensis, in East Hokkaido, Japan

Red-crowned cranes (Grus japonensis) are native to eastern Hokkaido (island population), in contrast to the mainland, which migrates between the Amur River basin and eastern China-Korea peninsula. During the 1990s we found that Red-crowned cranes in Hokkaido were highly contaminated with mercury: however, the source was unknown. We investigated the time trend of mercury contamination in Red-crowned cranes. Total mercury levels in the livers and kidneys from cranes dead in the 2000s were lower than those dead in the 1990s. Feather is a major pathway of mercury excretion for many bird species and is used as an indicator of blood mercury level during feather growth. As internal organs from the specimens collected before 1988 were not available, we analyzed the flight feather shavings from stuffed Red-crowned cranes dead in 1959-1987 and found that the mercury level of feathers from cranes dead in the 1960s and 1970s was not more than those from the cranes dead in the 2000s. These results suggest that mercury contamination in Red-crowned cranes in Hokkaido decreased temporally during the 1990s-2000s. This indicates the possible occurrence of some mercury pollution in Red-crowned cranes' habitat in this region in the 1990s or before.     

Mercury accumulation and excretion in laboratory reared black-headed gullLarus ridibundus chicks

Distribution of mercury between tissues was investigated in black-headed gull (Larus ridibundus) chicks fed doses of methyl mercury. Mercury accumulated differentially in the internal tissues, concentrations in the kidney exceeding those in the liver, which in turn exceeded those in the muscle. All feather types contained higher mercury concentrations than internal tissues. For each dose group, there was a progressive and pronounced reduction in the concentrations of mercury found in the primary feathers as the growth sequence progressed. The amount of mercury given to the birds affected the proportion of mercury deposited in the kidney, carcass, and primaries. The amount of mercury administered had no effect on the proportion of mercury excreted either in the faeces or the feathers. 71% of the doses given was excreted over the fledging period, and 49% of the dose was found in the plumage. These figures allow a more quantitative approach to measuring mercury pollution.     

Mercury in Wing and Tail Feathers of Hatch-Year and Adult Tidal Marsh Sparrows

We estimated mercury exposure and bioaccumulation in sparrow feathers to determine variation among age groups, between sparrow species, and between feather types. Results of feather mercury studies in piscivorous birds indicate that mercury concentrations tend to increase with age and differ between feather types; however, data for insectivorous birds are lacking. We estimated mercury exposure of two insectivorous and sympatric tidal marsh sparrows: coastal plain swamp sparrow (Melospiza georgiana nigrescens), and seaside sparrow (Ammodramous maritimus). Tidal marshes have favorable conditions for mercury methlyation, thus it is likely that tidal marsh sparrows are exposed to methylmercury. We found no difference in mercury concentrations between males and female birds of both species. Adult swamp sparrow feather mercury concentrations did not differ among adult age groups; therefore, mercury was not found to increase with age in sparrows at the site. Hatch-year birds had significantly greater feather mercury concentrations compared with adult birds for both species. Mercury concentrations in adult seaside sparrows were twice as high as those in adult swamp sparrows suggesting species-specific variation, although concentrations in hatch-year sparrow species did not differ. Mercury concentrations differed between feather types in adults of both species. The first primary feather of both species had at least three times greater mercury concentrations than the outer tail feather possibly reflecting varying depuration rates with feather type.     

Trace Element Concentrations (Mercury, Cadmium, Copper, Zinc, Lead, Aluminium, Nickel, Arsenic, and Selenium) in Some Aquatic Birds of the Southwest Atlantic Coast of France

Trace elements (mercury [Hg], cadmium [Cd], copper [Cu], zinc [Zn], lead [Pb], aluminium [Al], nickel [Ni], arsenic [As], and selenium [Se]) were investigated using inductively coupled plasma–mass spectrometry in liver, kidney, muscle, and feather of aquatic birds wintering or inhabiting the wetlands situated on the Southwest Atlantic coast of France. A majority of greylag geese, red knots, and grey plovers were collected from among hunter-shot animals. The relation between residue concentrations, age (juvenile vs. adult), and sex was investigated. Trace elements were lower than threshold levels of toxicity, except for Pb. Greylag geese sampled could be considered Pb-poisoned. These consequential levels of contamination could be the result of the ingestion of Pb-shot from ammunition used in hunting areas they crossed during migration. Cd accumulation increased with age, whereas Pb levels in feathers were lower in adult birds in connection with moulting. As was influenced by sex. Female birds displayed higher concentrations in liver and feathers than did male birds.