Can Excrement and Feathers of Nestling Songbirds Be Used as Biomonitors for Heavy Metal Pollution?

Although birds have been frequently used as indicators of heavy metal pollution, few studies have examined pollutant levels in nestling passerines. In this paper we determined the levels of two essential (zinc and copper) and three nonessential heavy metals (lead, cadmium, and arsenic) in the excrement and feathers of great (Parus major) and blue tit (Parus caeruleus) nestlings at a polluted site (near a metallurgic factory) and a reference site (4 km farther east). The excrement of both great and blue tit nestlings contained significantly higher concentrations of arsenic, cadmium, copper, and lead at the polluted site. Zinc concentrations did not differ significantly between sites for both species. The feathers of great and blue tit nestlings accumulated significantly higher concentrations of lead at the polluted site than at the reference site. Zinc levels in the feathers of great tit nestlings were significantly higher at the reference site than at the polluted site. For all other elements considered, concentrations did not differ significantly between the two sites. There were no interspecific differences in metal levels between great and blue tits in both excrement and feathers. There was a significant positive correlation between the lead concentration in the excrement and feathers for both great and blue tits. We therefore conclude that excrement of great and blue tit nestlings can be used as a biomonitor for heavy metals (lead, cadmium, arsenic, and copper), whereas feathers appear only to be suitable as a biomonitor for lead pollution. Received: 21 March 2000/Accepted: 9 July 2000     

Spatial and Temporal Variation of Lead,Cadmium, and Zinc in Feathers of Great Tit and Blue Tit Nestlings in Central Poland

In this study, we examined heavy-metal concentrations in feathers of nestling great tits Parus major and blue tits Cyanistes caeruleus at two different sites (urban parkland vs. deciduous forest) located in the ?ód? agglomeration in relation to interyear variation. We found that tit species did not differ significantly in lead and cadmium concentrations. Zinc concentration was significantly higher in blue tits. We also found that lead and cadmium levels in blue tit nestlings and the level of lead in great tit nestlings were higher in the parkland site than in the woodland site. We explain habitat variation in heavy-metal concentrations in feathers of nestlings by different levels of contamination at study sites. For both tit species, significant variation in heavy-metal amounts accumulated by nestlings was found between years with the lowest value in a year with the lowest value of rainfall. We suggest that the interyear variation may be accounted for by differences in rainfall, thus influencing quantities of trace elements bioavailable in the environment.     

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.     

Lead in Feathers and δ-Aminolevulinic Acid Dehydratase Activity in Three Raptor Species from an Unpolluted Mediterranean Forest (Southeastern Spain)

This paper presents the levels of lead found in the feathers of adult and blood of nestlings of booted eagle (Hieraaetus pennatus), European buzzard (Buteo buteo), and goshawk (Accipiter gentilis) sampled in the 1999 and 2000 breeding seasons in a Mediterranean forest of the Province of Murcia (Southeastern Spain) located far from potential sources of metal contamination. Levels of -aminolevulinic acid dehydratase activity (-ALAD) in blood were also measured in the nestlings. Lead concentrations ranged from 1.1 to 11.21 g/dl in blood of nestlings and from 0.35 to 1.66 mg/kg d.w. in the feathers of their parents. A significant relationship was found between blood -ALAD and lead ( = –568), showing a negative correlation with blood lead levels even at lead concentrations below 5 g/dl. This fact suggests the usefulness of this enzymatic biomarker for low lead exposure in forest raptors. There were also positive relationships between the lead concentrations in blood of nestlings and those in feathers of their parents ( = 0.817), suggesting the usefulness of feathers for biomonitoring environmental exposure to lead.     

Mercury Distribution in Blood, Tissues, and Feathers of Double-Crested Cormorant Nestlings from Arid-Lands Reservoirs in South Central New Mexico

Eggs, blood, liver, muscle, and feathers were analyzed for concentrations of total mercury in double-crested cormorant (Phalacrocorax auritus) nestlings from two reservoirs in south central New Mexico. Total mercury concentrations among eggs, tissues, and feathers were not significantly correlated. Concentrations of total mercury averaged 0.40 μg/g in liver and 0.18 μg/g in muscle tissues in both populations of nestlings. There were no significant changes in concentrations of total mercury in whole blood of nestlings collected 7–10 days and 17–22 days posthatch in Caballo Reservoir (0.36 μg/g and 0.39 μg/g, respectively) and in Elephant Butte Reservoir (0.36 μg/g and 0.34 μg/g, respectively). Total mercury concentrations were similar for blood, muscle, and liver in nestlings for both reservoirs. Total mercury concentrations were higher in eggs and tail, primary, and secondary feathers from nestlings at Caballo Reservoir compared to Elephant Butte Reservoir. Although there were no differences in concentrations of total mercury in fishes between the two reservoirs, bioaccumulation and biomagnification was evident in planktivorous and piscivorous fishes. The data demonstrate that feather analysis may not be a good predictor of tissue burden in nestlings from regions of low contamination. Received: 8 July 1998/Accepted: 20 December 1998     

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     

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.     

Inter- and intraclutch variability in heavy metals in feathers of great tit nestlings ( Parus major) along a pollution gradient

Heavy metal (silver, arsenic, cadmium, copper, mercury, lead, and zinc) concentrations were analyzed in feathers of nestling great tits ( Parus major) collected along a pollution gradient. Differences in metal concentrations along the gradient and inter- and intraclutch variability were investigated. In the immediate vicinity of the pollution source, feathers of nestling great tits contained significantly higher concentrations of silver, arsenic, mercury, and lead than at the sites further along the gradient. The concentrations of copper and zinc, two essential metals, were significantly lower at the second most polluted site. There was no significant difference in cadmium concentrations among sites. Most metals, except cadmium, were significantly positively correlated with each other. There was a significant amount of interclutch variability in feather metal concentrations, and they differed significantly among sites. The amount of inter- and intraclutch variability did not differ significantly, although intraclutch variability of most metals was markedly high. Our study indicates that feathers of great tit nestlings could be used as bioindicators of metal pollution, but attention should be paid in designing representative sampling procedures.     

Inter- and Intraclutch Variability in Heavy Metals in Feathers of Great Tit Nestlings (Parus major) Along a Pollution Gradient

Heavy metal (silver, arsenic, cadmium, copper, mercury, lead, and zinc) concentrations were analyzed in feathers of nestling great tits (Parus major) collected along a pollution gradient. Differences in metal concentrations along the gradient and inter- and intraclutch variability were investigated. In the immediate vicinity of the pollution source, feathers of nestling great tits contained significantly higher concentrations of silver, arsenic, mercury, and lead than at the sites further along the gradient. The concentrations of copper and zinc, two essential metals, were significantly lower at the second most polluted site. There was no significant difference in cadmium concentrations among sites. Most metals, except cadmium, were significantly positively correlated with each other. There was a significant amount of interclutch variability in feather metal concentrations, and they differed significantly among sites. The amount of inter- and intraclutch variability did not differ significantly, although intraclutch variability of most metals was markedly high. Our study indicates that feathers of great tit nestlings could be used as bioindicators of metal pollution, but attention should be paid in designing representative sampling procedures. Received: 2 July 2001/Accepted: 25 March 2002     

The use of novel biomarkers to determine dietary mercury accumulation in nestling waterbirds

Mercury (Hg) depuration into growing feathers is a well-studied phenomenon in waterbirds. Although the kinetics of Hg excretion in relation to molt and diet has been studied extensively, the relationship between the individual nutritional condition of nestlings and dietary Hg accumulation has not been investigated. In the present study, a body-condition index (BCI) and nutritional condition index (NCI) for nestlings of two waterbird species occupying different trophic positions on the aquatic food web were determined and used to predict Hg accumulation through diet. Candidate models consisting of these indices and nestling age were compared using Akaike's information criterion corrected for small sample sizes. For both species, the top-performing model contained the sole parameter of nutritional condition index (NCI). The relationship between Hg and NCI was stronger in the species foraging higher on the trophic web, which experienced higher rates of Hg depuration into feathers. Models containing BCI could not be discounted (AICc?相似文献   

Developmental toxicity of in ovo exposure to polychlorinated biphenyls: I. Immediate and subsequent effects on first-generation nestling American kestrels (Falco sparverius)

We determined that in ovo exposure to polychlorinated biphenyls (PCBs) alters growth of first-generation nestlings during and one year after parental exposure. Captive American kestrels (Falco sparverius) laid eggs with environmentally relevant total PCB levels (34.1 microg/g whole-egg wet wt) when fed PCB-spiked (Aroclor 1248, 1254, and 1260) food (7 mg/kg body wt/ d) for 100 d in 1998. In 1999, the same adults laid eggs with estimated total PCBs of 29.0 microg/g. Nonsurviving PCB-exposed chicks were small (mass, bones) in 1998. Survivors showed a strong sex-specific growth response (mass, bones) compared to respective sex controls: Only female hatchlings were larger, and only male nestlings had longer feathers (1998); maximal growth and bone growth rates also differed (males were advanced, faster; females delayed, slower) (1999); and male nestlings fledged earlier and were smaller, while females were larger (1998, 1999). However, regardless of sex, PCB-exposed nestlings generally grew at faster rates in both years. In 1998, greater contaminant burdens and toxic equivalent concentrations in sibling eggs were associated with nestlings being lighter, having longer bones and feathers, and growing at faster rates (mass, bone) for females but slower rates (mass) for males. Both physiological-biochemical and behavioral changes are likely mechanisms. This study supports and expands on the Great Lakes embryo mortality, edema, and deformities syndrome: While PCB exposure alters nestling size, maximal growth and growth rates also change immediately, are sustained, and are sex specific.     

Heavy Metal, Organochlorine Pesticide, and PCB Residues in Eggs and Feathers of Herons Breeding in Northern Italy

We report on organochlorine pesticide and PCB concentrations in eggs of the little egret, Egretta garzetta, and the black-crowned night-heron, Nycticorax nycticorax, collected in 1993–1994, and on mercury, cadmium, and lead concentrations in feathers of 20-day-old nestlings collected from the same nests in 1994, from heronries near Pavia, northern Italy. Organochlorine pesticide and PCB residues were lower than those commonly associated with mortality and reduced reproductive success. As population levels of the species studied are not declining, these contaminants appear to have no significant adverse effect on reproduction in the heronries studied. DDE levels have decreased markedly in heron eggs since 1978. However, the presence of both DDT and β-HCH, albeit at low levels, is notable, given that these compounds were banned in Italy in 1978 and 1988, respectively. Relatively high levels of Hg, Cd, and Pb in feathers suggest birds in their colonies are exposed to these contaminants, although both Cd and Pb may relate more to external than to internal contamination. Received: 1 February 1997/Accepted: 5 May 1997     

Tissue Levels of Lead in Experimentally Exposed Zebra Finches (Taeniopygia guttata) with Particular Attention on the Use of Feathers as Biomonitors

We tested experimentally whether zebra finch feathers can be used as a biomonitor for lead pollution, and we examined whether lead exposure influences the accumulation of zinc into feathers. Two groups of eight adult male zebra finches were dosed with, respectively, 0 and 25 ppm lead as lead acetate in their drinking water. After 30 days, lead-treated zebra finches accumulated significantly higher lead concentrations in brain, fat, kidney, liver, muscle, testes, and regrown outer tail feathers than control individuals. Lead levels in regrown outer tail feathers were significantly higher than in original outer tail feathers in the exposed group. The concentration of lead in original (not regrown) fifth tail feathers at the end of the experiment was significantly higher than lead levels in the original outer tail feathers. Our results indicate that lead in regrown feathers originates both from internal deposition and external contamination through the excretion of the uropygial gland during preening. Lead levels in regrown feathers were significantly correlated with levels in liver, kidney, and muscle, suggesting that feathers can be used as a biomonitor for lead. We found that lead had an influence on the metabolism of zinc. Zinc concentrations in the regrown feathers were significantly lower in the lead-treated group although zinc levels in the liver did not differ significantly. Moreover, lead and zinc concentrations in the feathers were significantly negatively correlated. Received: 30 January 2001/Accepted: 1 July 2001     

The Use of Feathers to Monitor Heavy Metal Contamination in Herons, Korea

This study measured concentrations of iron, manganese, zinc, copper, lead, and cadmium in environmental substrates (water and sediment) as well as in the diet and feathers of Black-crowned Night Heron Nycticorax nycticorax and Grey Heron Ardea cinerea chicks from Pyeongtaek heronry, Gyeonggi-do, Korea. Zinc and cadmium concentrations in sediment were relatively high, but lead was low. In the diet, only copper concentrations were higher in Black-crowned Night Herons than in Grey Herons. Cadmium concentrations in the diet of two heron species from a Pyeongtaek heron colony were also higher than reported in other studies. In feathers, iron, copper, and lead concentrations were significantly different between heron species. Iron and copper concentrations were higher in Black-crowned Night Heron chicks than in Grey Heron chicks, but lead concentrations were not. Therefore, with the exception of lead, heavy metal concentrations in feathers were not related to concentrations in the diet. Zinc, iron, and lead concentrations in heron feathers were within the ranges reported by other heron studies, but manganese, copper, and cadmium were much higher. Lead and cadmium concentrations in feathers of Black-crowned Night Heron and Grey Heron chicks were elevated to lead and cadmium concentrations in the diet. Therefore, we suggest that lead and cadmium concentrations in heron feathers reflect contamination of breeding sites and are useful bioindicators of local contamination. An erratum to this article is available at .     

Mercury in eggs and feathers of great egrets (Ardea albus) from the Florida Everglades

Great egret (Ardea albus) eggs and nestling feathers were collected for total mercury (THg) and methylmercury (MeHg) analysis from two colonies in the Florida Everglades in 1999 and 2000. THg was present in all eggs at a mean concentration of 0.39 ± 0.19 μg/g fresh weight (n = 33, range = 0.08–0.86 μg/g). Egg-THg levels did not differ significantly between colonies or years. MeHg concentration in eggs was 0.35 ± 0.18 μg/g fresh weight (n = 20, range = 0.05–0.82 μg/g,), and on average represented 85% of the THg found in the egg. Concentration of THg in feathers from egret nestlings, age 11–31 days, ranged from 1.4 to 8.6 μg/g dry weight. Feather-THg levels also did not differ significantly between colonies or years. THg concentrations in feathers, normalized based on bill length, were positively correlated to THg concentrations in eggs from the same clutch. Levels of THg in both eggs and feathers were lower in 1999 and 2000 than values reported for similar samples collected in 1993–95, indicating that MeHg exposure has decreased in the southern Everglades since the mid-1990s. THg levels in eggs and nestling feathers for the period of this study were below levels associated with toxic reproductive effects. Clutch size, fledging success, and brood size observed in this study were consistent for this species in the Everglades. Collectively, these results suggest that MeHg was not adversely affecting the reproductive performance of this population during the study. Received: 20 December 2000/Accepted: 30 August 2001     

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.     

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.     

Heavy Metal Concentrations in Feathers of Korean Shorebirds

This study presents concentrations of zinc, manganese, copper, lead, and cadmium in the feather of five shorebird species from Yeongjong Island, Korea in the East Asian–Australian migration flyways. The objectives of this study were to determine levels of heavy metal concentrations in the feathers of shorebirds, to evaluate the pattern of heavy metal concentrations in the feather and the liver, and to examine the correlation between heavy metal concentrations in the feathers and livers. We hypothesized that difference of heavy metal concentrations will show by the breeding ground of shorebirds. Lead concentrations in dunlins (geomean = 14.8 μg/g wet weight) and great knots (20.8 μg/g wet weight) feathers were significantly higher than Terek sandpipers (3.32 μg/g wet weight); other metals were not different among shorebirds. Zinc, lead, and cadmium concentrations in the feather were correlated with the liver concentrations, but manganese and copper concentrations were not. Zinc, manganese, copper, lead, and cadmium concentrations in the feather from this study were within the range of earlier studies for wild birds, but cadmium concentrations in dunlins were higher than other studies. Because lead concentrations in livers and feathers of the Terek sandpiper were lower than in other shorebirds, we suggest that Terek sandpipers were exposed to lower lead concentrations than Kentish plovers, dunlins, and great knots on their breeding ground. An erratum to this article can be found at     

Developmental Toxicity of Three Carrier Solvents Using Embryos of the Grass Shrimp, Palaemonetes pugio

Herons and egrets are ideal organisms to use as indicators of heavy metal exposure in an ecosystem because different species feed at different levels of the food chain and live in both coastal and inland habitats. This paper reports on the concentration of heavy metals and selenium in the feathers of cattle egrets Bubulcus ibis that were examined from nesting and roosting sites in Bali and Sulawesi, Indonesia, and in feathers of little egrets Egretta garzetta and intermediate egrets E. intermedia from the same colony in Bali. Mercury and manganese concentrations were significantly higher in cattle egrets from Bali compared to Sulawesi, but otherwise there were no significant differences. There were significant differences in lead, cadmium and mercury among the three egret species nesting on Bali: 1) the cadmium and mercury concentrations related to size and trophic level (insectivorous cattle egrets had the lowest concentrations, fish-eating intermediate egrets had the highest concentrations), and 2) cattle egrets had significantly lower concentrations of lead than the other two species. For cattle egrets, secondary flight feathers had significantly higher levels of cadmium and mercury, and lower levels of manganese, than mixed breast and tertiary feathers, reflecting temporal differences in exposure. Received: 28 May 1996/Revised: 2 August 1996     

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.