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USGS · 70159551

Egg laying sequence influences egg mercury concentrations and egg size in three bird species: Implications for contaminant monitoring programs

Joshua T. Ackerman·Collin A. Eagles-Smith·Mark P. Herzog·Julie L. Yee·C. Alex Hartman
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Abstract

Bird eggs are commonly used in contaminant monitoring programs and toxicological risk assessments, but intra-clutch variation and sampling methodology could influence interpretability. We examined the influence of egg laying sequence on egg mercury concentrations and burdens in American avocets, black-necked stilts, and Forster's terns. The average decline in mercury concentrations between the first and last egg laid was 33% for stilts, 22% for terns, and 11% for avocets, and most of this decline occurred between the first and second eggs laid (24% for stilts, 18% for terns, and 9% for avocets). Trends in egg size with egg laying order were inconsistent among species and overall differences in egg volume, mass, length, and width were <3%. We summarized the literature and, among 17 species studied, mercury concentrations generally declined by 16% between the first and second eggs laid. Despite the strong effect of egg laying sequence, most of the variance in egg mercury concentrations still occurred among clutches (75%-91%) rather than within clutches (9%-25%). Using simulations, we determined that to accurately estimate a population's mean egg mercury concentration using only a single random egg from a subset of nests, it would require sampling >60 nests to represent a large population (10% accuracy) or &ge;14 nests to represent a small colony that contained <100 nests (20% accuracy).

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Joshua T. Ackerman, Collin A. Eagles-Smith, Mark P. Herzog, Julie L. Yee, C. Alex Hartman. 2015-10-27. Egg laying sequence influences egg mercury concentrations and egg size in three bird species: Implications for contaminant monitoring programs. https://doi.org/10.1002/etc.3291

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