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TRACING NUTRIENT ALLOCATION TO REPRODUCTION IN BARROW'S GOLDENEYE
Author(s) -
HOBSON KEITH A.,
THOMPSON JONATHAN E.,
EVANS MATTHEW R.,
BOYD SEAN
Publication year - 2005
Publication title -
the journal of wildlife management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.94
H-Index - 111
eISSN - 1937-2817
pISSN - 0022-541X
DOI - 10.2193/0022-541x(2005)069[1221:tnatri]2.0.co;2
Subject(s) - δ13c , yolk , δ15n , anatidae , biology , nutrient , stable isotope ratio , isotope analysis , range (aeronautics) , precocial , trophic level , zoology , reproduction , isotope , ecology , bird egg , isotopes of carbon , physics , materials science , quantum mechanics , composite material , total organic carbon
Naturally occurring stable isotopes in foodwebs can be used to determine the relative contributions of endogenous and exogenous nutrients to avian eggs in cases where birds move between isotopically distinct biomes or habitats to breed. We measured δ 13 C and δ 15 N values in somatic muscle tissues and eggs of Barrow's goldeneye ( Bucephala islandica ) together with those isotope values in amphipods from wetlands used by birds breeding on the Chilcotin Plateau in central British Columbia, Canada. Females that had recently arrived on the breeding grounds had muscle tissue isotope values similar to those found in coastal wintering birds and were considerably more enriched in C than were samples from local foodwebs. However, δ 15 N values of amphipods were highly variable among wetlands, resulting in a nondistinct exogenous δ 15 N endpoint for our dual‐isotope mixing model. Therefore, we only used the model based on δ 13 C values to estimate nutrient sources to eggs. In 2000, first‐laid eggs were more enriched in both isotopes than fourth‐ or eighth‐laid eggs. Considerable endogenous protein input to egg yolk and albumen was detected for the first laid egg (yolk: range = 0–92.7%, median = 23.7%; albumen: range = 0–78.6%, median = 28.7%) with less endogenous contribution of somatic lipids (first egg: range = 0–100%, median = 4.9%). Using archived tissue samples of muscle and developing ovarian follicles from birds collected in 1993–1994, we found no δ 13 C isotopic evidence for endogenous protein contribution to egg yolk. Our results demonstrate the utility of the stable isotope approach in cases where isotopic endpoints are well established. Barrow's goldeneye showed a mixed strategy of endogenous vs. exogenous nutrient allocation to reproduction that varied by individual females, laying order, and year. We encourage managers to use this approach to quantify nutrient allocations from various biomes to reproduction in waterfowl to better understand the importance of wintering sites to reproduction.