Diet shifts during egg laying: Implications for measuring contaminants in bird eggs.
We combined stable isotope tracers of blood plasma, blood cells and egg contents with faecal analysis during pre-breeding and egg laying phases in two dipper species Cinclus cinclus and Cinclus mexicanus to determine the occurrence of dietary shifts during egg production and to assess consequences for egg contaminant loads. In both species, changes in delta(13)C (C. cinclus) or delta(15)N (C. mexicanus) in female plasma relative to red blood cells indicated a dietary shift during laying that was not observed in males. Eurasian dippers increased prey consumption as breeding approached, shifting from primarily trichopteran insect larvae to ephemeropterans and plecopterans. In American dippers, egg-laying females switched to feeding at a higher trophic level by consuming more fish. Eggs derived from higher trophic level diets contained more mercury (American dipper), polychlorinated biphenyls and some organochlorines, especially DDT metabolites. The results demonstrate how dietary changes during egg laying accompany the demands for egg production with consequences for contaminant deposition in avian eggs.
Morrissey
Christy A
CA
Catchment Research Group, School of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom.
Elliott
John E
JE
Ormerod
Stephen J
SJ
D000704:Analysis of Variance; D000818:Animals; D001955:British Columbia; D002247:Carbon Isotopes / Q000097:blood; D004032:Diet; D004785:Environmental Pollutants / Q000032:analysis; D004912:Erythrocytes / Q000737:chemistry; D005243:Feces / Q000737:chemistry; D005260:Female; D007553:Isotope Labeling; D008297:Male; D009587:Nitrogen Isotopes / Q000097:blood; D010058:Oviposition / Q000502:physiology*; D010063:Ovum / Q000737:chemistry*; D046109:Passeriformes / Q000502:physiology*; D012737:Sex Factors; D013045:Species Specificity
D002247:Carbon Isotopes; D004785:Environmental Pollutants; D009587:Nitrogen Isotopes