Primary Molt of California Condors

Snyder, Noel F. R.; Johnson, Eric V.; Clendenen, David A.

doi:10.2307/1368637

Cited by 35 publications

(34 citation statements)

References 8 publications

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“…Since condor feathers can grow ∼5 mm/day, they may provide a detailed record of the bird's lead exposure history over the period of feather growth, which may be several months (47). Lead concentrations were lowest in the older (distal) part of the feather rachis and vane, and sharply increased to higher values in the younger (proximal) part of the feather (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Ammunition is the Principal Source of Lead Accumulated by California Condors Re-Introduced to the Wild

Church

Gwiazda

Risebrough

et al. 2006

Environ. Sci. Technol.

159

105

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The endangered California Condor (Gymnogyps californianus) was reduced to a total population of 22 birds by the end of 1982. Their captive-bred descendants are now being released back into the wild in California, Arizona, and Baja California, where monitoring indicates they may accumulate lead to toxic levels. Fragments of ammunition in the carcasses of game animals such as deer, elk, and feral pigs not retrieved by hunters or in gut piles left in the field have been considered a plausible source of the lead, though little direct evidence is available to support this hypothesis. Here, we measured lead concentrations and isotope ratios in blood from 18 condors living in the wild in central California, in 8 pre-release birds, and in diet and ammunition samples to determine the importance of ammunition as a source of exposure. Blood lead levels in pre-release condors were low (average 27.7 ng/mL, SD 4.9 ng/mL) and isotopically similar to dietary and background environmental lead in California. In contrast, blood lead levels in free-flying condors were substantially higher (average 246 ng/mL, SD 229 ng/mL) with lead isotopic compositions that approached or matched those of the lead ammunition. A two-endmember mixing model defined by the background 207Pb/206Pb ratio of representative condor diet samples (0.8346) and the upper 207Pb/206Pb ratio of the ammunition samples (0.8184) was able to account for the blood lead isotopic compositions in 20 out of the 26 live condors sampled in this study (i.e., 77%). Finally, lead in tissues and in a serially sampled growing feather recovered post-mortem from a lead-poisoned condor in Arizona evidence acute exposure from an isotopically distinct lead source. Together, these data indicate that incidental ingestion of ammunition in carcasses of animals killed by hunters is the principal source of elevated lead exposure that threatens the recovery in the wild of this endangered species.

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Section: Resultsmentioning

confidence: 99%

Ammunition is the Principal Source of Lead Accumulated by California Condors Re-Introduced to the Wild

Church

Gwiazda

Risebrough

et al. 2006

Environ. Sci. Technol.

159

105

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“…1; Table 2). Whole blood is the only tissue in which we could compare chicks and juveniles because the condor's molt pattern is such that the juveniles did not have feathers growing during the period in which they were held on the controlled diet (Snyder et al 1987). Our study provides the first diet-tissue discrimination factors reported for New World vultures (family Cathartidae) from multiple tissues, ages, and experimental diets.…”

Section: Juvenilesmentioning

confidence: 98%

Discrimination Factors for Stable Isotopes of Carbon and Nitrogen in Blood and Feathers from Chicks and Juveniles of the California Condor

et al. 2013

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Abstract. Stable-isotope ratios of carbon ( 13 C/ 12 C; δ 13 C) and nitrogen ( 15 N/ 14 N; δ 15 N) in animal tissues are analyzed to estimate animal foraging ecology because these ratios reflect those of an animal's diet. This reflection is generally indirect, as stable-isotope ratios change with trophic level. These differences, called discrimination factors (reported as Δ), vary considerably by species and tissue. Variations in discrimination factors used in stableisotope mixing models can lead to inaccurate estimates of diets. Therefore, determining accurate discrimination factors specific to species and tissue is important. We established the Δ 13 C and Δ 15 N values between diet and blood and feathers from chicks and juveniles of the California Condor (Gymnogyps californianus). hatchlings were fed rats for 76-119 days, whereas juveniles were fed dairy calves for 64 days. The mean Δ 13 C and Δ 15 N values (± SD) between chick feathers and rat muscle were 0.4 ± 0.4‰ and 3.1 ± 0.2‰, respectively; those between chicks' whole blood and rat muscle were -0.7 ± 0.1‰ and 1.7 ± 0.1‰, respectively. The mean Δ 13 C and Δ 15 N values between juvenile condors' plasma and calf muscle were 0.9 ± 0.2‰ and 3.3 ± 0.7‰, respectively; those between juveniles' red blood cells and calf muscle were 0.3 ± 0.3‰ and 1.8 ± 0.1‰, respectively; and those between juveniles' whole blood and calf muscle were 0.3 ± 0.3‰ and 1.9 ± 0.2‰, respectively. We report the first discrimination factors for the Cathartidae (New World vultures), and our findings will have important applications in studies of the critically endangered California Condor's foraging ecology.

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“…Both ␦ 13 C and ␦ 15 N isotope values can vary within individual feathers (19) and depend upon the diet of the condor during the period of feather growth (9). Most primary feathers of condors are shed between February and September and are replaced over a period of 4 months (20). Thus, we would expect some degree of isotopic variability within a given feather, particularly because the scavenging diet of condors can be highly variable.…”

Section: Methodsmentioning

confidence: 99%

“…Our criteria for selecting feathers was: (i) we used only growing feathers or the portions of these feathers that were generated after release or (ii) we used fully grown feathers from birds that had been in the wild for at least 850 days. This criterion assumes that feathers are replaced every 2 years and it takes Ϸ4 months to form a full primary feather (20). Table 2).…”

Section: Methodsmentioning

confidence: 99%

Pleistocene to recent dietary shifts in California condors

Chamberlain

Waldbauer²,

Fox-Dobbs³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

164

142

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We used carbon and nitrogen isotopes to investigate changes in the diet of California condors from the Pleistocene to the recent. During the Pleistocene, condors from California fed on both terrestrial megafauna and marine mammals. Early accounts reported condors feeding on the carcasses of marine mammals, but by the late 1700s, condor diets had shifted predominantly to terrestrial animals, following the commercial harvesting of marine mammals and the development of cattle ranching on land. At present, dairy calves provided by humans significantly augment condor diet, constituting an artificial support of the current population. Reestablishing a marine mammal component in the condor diet may be an effective strategy for fostering viable condor populations independent of direct human subsidies.carbon isotopes ͉ nitrogen isotopes ͉ paleodiet D uring the Pleistocene, California condors (Gymnogyps californianus) ranged from the Pacific coast of North America across the southern U.S. to Florida and north to western New York (1, 2). Historical records show that by the 17th century, condors were restricted to the west coast of North America, from Baja California to British Columbia (3, 4). At present, small reintroduced populations live in California, Arizona, and Baja California. Paleontological evidence suggests that populations of these obligate scavengers were associated with the carcasses of large animals (1). After the late Pleistocene extinction of most large terrestrial mammals in North America (5), condors appear to have been restricted to the west coast, where stranded marine mammals offered the only remaining abundant source of large animal carcasses (1).There is little direct evidence that marine mammals were a significant component of condor diets, however, beyond scattered historical observations. In 1806, Lewis and Clark observed condors feeding on whales near the mouth of the Columbia River (6). Captain Clark wrote on February 16, 1806: ''This bird fly's very clumsily, nor do I know whether it ever seizes it's prey alive, but am induced to believe it does not. We have seen it feeding on the remains of the whale and other fish which have been thrown up by the waves on the sea coast. These I believe constitute their principal food, but I have no doubt but that they also feed on flesh.'' In 1855, Taylor found hundreds of condors feeding on sea lion carcasses on the California coast (7). He wrote: ''During the early part of the present month, large quantities of sea lions have been killed on the southern coast for the oil; the carcasses of these animals on the beach may be seen at times surrounded by hundreds of the Condors. A friend of ours informed us that he saw a few days ago, as many as three hundred of these creatures near such feeding ground, within a distance of a league.'' (7). In the 1860s, Cooper reported on condors feeding on seal and whale carcasses in California, although he never directly observed them doing so (8).To investigate changes in condor diets, we determined the stable carbon ( 12 C...

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Primary Molt of California Condors

Cited by 35 publications

References 8 publications

Ammunition is the Principal Source of Lead Accumulated by California Condors Re-Introduced to the Wild

Ammunition is the Principal Source of Lead Accumulated by California Condors Re-Introduced to the Wild

Discrimination Factors for Stable Isotopes of Carbon and Nitrogen in Blood and Feathers from Chicks and Juveniles of the California Condor

Pleistocene to recent dietary shifts in California condors

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