USE OF BODY STORES IN SHOREBIRDS AFTER ARRIVAL ON HIGH-ARCTIC BREEDING GROUNDS

Stable-isotope analyses of egg components can illuminate the contributions of endogenous and exogenous nutrients to egg formation in cases where birds move from one isotopic biome to another just before egg-laying, as in Red Knots (Calidris canutus islandica) and Ruddy Turnstones (Arenaria interpres...

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Bibliographic Details
Published in:The Auk 2004-04, Vol.121 (2), p.333-344
Main Authors: Morrison, R. I Guy, Hobson, Keith A
Format: Article
Language:English
Subjects:
Animal populations
Animal reproduction
Birds
Breeding of animals
Habitats
Ornithology
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Summary:Stable-isotope analyses of egg components can illuminate the contributions of endogenous and exogenous nutrients to egg formation in cases where birds move from one isotopic biome to another just before egg-laying, as in Red Knots (Calidris canutus islandica) and Ruddy Turnstones (Arenaria interpres interpres) nesting in the northeastern Canadian High Arctic. Those populations use inshore marine habitats during the winter and northward migration periods, but switch to feeding and breeding in terrestrial C-3 habitats in the Arctic. Upon the birds' arrival at Alert, Nunavut, Canada, stable carbon (δ13C) and nitrogen (δ15N) isotope values for their red blood cells were consistent with those expected from an inshore marine diet. After the birds switched to a terrestrial diet, those values decayed in a negative exponential fashion until they reached asymptotic values consistent with a local terrestrial C-3 diet. Components of eggs laid later in the season, including lipid-free yolk, albumen, yolk lipid, and albumen lipid, generally showed isotope values consistent with routing from exogenous (i.e. local) nutrient sources, which supports the notion that High Arctic shorebirds are primarily income and not capital breeders. However, eggs in earliest clutches were enriched in 13C and 15N, which suggests that some residual marine nutrients were available for reproduction. The extent to which endogenous stores are transferred to eggs in High Arctic shorebirds may depend on year and climatic conditions.
ISSN:0004-8038
1938-4254
2732-4613
DOI:10.1642/0004-8038(2004)121[0333:UOBSIS]2.0.CO;2