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White-faced ibis populations and pollutants in Texas, 1969-1976

Southwestern Naturalist

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Abstract

Eggshell thickness, levels of pollutant residues, and population status of the white-faced ibis (Plegadis chihi) were monitored in Texas from 1969 through 1976. Texas ibis nesting populations declined by 42%. Reproductive success apparently was limited by DDE-induced shell thinning and by dieldrin-caused mortality. Eggshells averaged 4% to 10% thinner than the pre-1943 mean thickness. Shells of numerous crushed eggs exceeded 20% thinning. Mean DDE residues in randomly collected eggs decreased from 0.94 ppm in 1970 to 0.25 ppm in 1976. DDE was higher, averaging 2.5 ppm, in thin-shelled eggs. DDE was negatively correlated with shell thickness. Dieldrin and PCB residues increased slightly from 1970 to 1976, but neither was correlated significantly with shell thickness. Residues in brains of many dead and dying ibises collected during years of extreme reproductive failure, 1970 and 1973, contained between 5 and 25 ppm dieldrin. Ibises were exposed to aldrin and dieldrin by feeding in rice fields where aldrin-treated rice seed was planted. Improved nesting success in 1976 may have been related to declining residues of DDE and to the discontinued use of aldrin in rice fields.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
White-faced ibis populations and pollutants in Texas, 1969-1976
Series title:
Southwestern Naturalist
Volume
25
Issue:
2
Year Published:
1980
Language:
English
Contributing office(s):
Patuxent Wildlife Research Center
Description:
225-240
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Southwestern Naturalist
First page:
225
Last page:
240
Number of Pages:
16