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Eggshell Characteristics and Organochlorine Residues in Common Terns: Variation with Egg Sequence

Ian C. T. Nisbet
Colonial Waterbirds
Vol. 5 (1982), pp. 139-143
Published by: Waterbird Society
DOI: 10.2307/1521045
Stable URL: http://www.jstor.org/stable/1521045
Page Count: 5
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Eggshell Characteristics and Organochlorine Residues in Common Terns: Variation with Egg Sequence
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Abstract

Oological characters and organochlorine concentrations were measured in 10 three-egg clutches of Common Terns. Designating the first, second, and third eggs by A, B, and C, respectively, C-eggs were significantly smaller and lighter than A-eggs and had thinner and lighter shells. Organochlorine concentrations were generally higher by about 20% (range, 0-29%) in C-eggs than in A-eggs. B-eggs were intermediate in most of these respects. The differences in organochlorine concentrations may be related to changes in the lipid balance of females during the egg-laying period. The differences in eggshell thickness were parallel to differences in egg dimensions, and cannot be attributed to the small differences in DDE levels. Implications for the conduct of field studies are discussed.

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