Datasets / Contaminants in Waterbirds, Grackles, and Swallows Nesting on the Lower Colorado River, Arizona, 2000-2001


Contaminants in Waterbirds, Grackles, and Swallows Nesting on the Lower Colorado River, Arizona, 2000-2001

Published By US Fish and Wildlife Service, Department of the Interior

Issued almost 10 years ago

US
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Summary

Type of release
a one-off release of a single dataset

Data Licence
Not Applicable

Content Licence
Creative Commons CCZero

Verification
automatically awarded

Description

Levels and potential effects of organochlorine compounds and metals were assessed in 106 eggs representing nine avian species nesting at four lower Colorado River National Wildlife Refuges. Geometric mean DDE residues were highest in the eggs of whitefaced ibis Pegadis chihi 2.34 ugg wet weight and doublecrested cormorant Phalacrocorax auritus 0.75 ugg wet weight. Whitefaced ibises fledged 1.0 young per pair and reproductive success was limited by DDEinduced eggshell thinning and by potentially embryotoxic 4.0 ugg DDE residues detected in 48 of the eggs. Mean shell thickness of 23 ibis eggs was 0.264 mm, 15 thinner than shells of eggs collected before the widespread use of DDT P0.0001. DDE was negatively correlated r 0.51, P0.0001 with eggshell thickness. DDT, the parent compound, was detected in 9 of 23 ibis eggs. DDE in 4 of 22 cormorant eggs 18 approached or exceeded the lowest observed adverse effect level. Eggshell thickness averaged 0.412 mm, 4.2 thinner than preDDT museum eggs 0.43 mm. DDE residues in cormorant eggs were not correlated P0.3628 with shell thickness. Almost onehalf 613 the cormorant eggs collected in 2000 were addled. Overall cormorant reproductive success was 1.0 young fledged per pair. Low DDE residues 0.70 ugg wet weight were detected in the eggs of Clarks grebe Aechmophorus clarkii, least bittern Ixobrychus exilis, and greattailed grackle Quiscalus mexicanus. A single great blue heron Ardea herodias egg contained 4.10 ugg DDE, a level above the threshold where embryotoxic effects might be expected. Mercury was present at background levels in all fisheating birds and in all but one ibis egg. In the eggs of omnivorous bird species, American coots Fulica americana and greattailed grackles, mercury was detected in 50 of the eggs. Eggs and nestlings of the primarily insectivorous cliff swallow Petrocheliodon pyrrhonota did not contain detectable mercury concentrations. Mercury does not appear to be a contaminant of concern for birds nesting along the lower Colorado River. Of 106 eggs collected from nine species, more than onethird 39106 contained potentially embryotoxic 6.0 ugg concentrations of selenium. The frequency of occurrence of elevated levels of selenium was greatest in eggs of western Aechmophorus occidentalis 87 and Clarks grebe 76. Generally, eggs of fisheating birds contained the highest concentrations of selenium, followed by eggs of omnivorous species. None of the eggs of the insectivorous cliff swallow contained selenium above the 6.0 ugg toxic threshold. Selenium concentrations were higher in swallow nestlings than in eggs suggesting that selenium bioaccumulation occurred during the first 10days of life.