Inter-annual variability in diet of non-breeding pelagic seabirds Puffinus spp. at migratory staging areas: evidence from stable isotopes and fatty acids

Autor: H. N. Koopman, Andrew J. Westgate, Robert A. Ronconi, C. A. E. McKinstry, S. N. P. Wong
Rok vydání: 2010
Předmět:
Zdroj: Marine Ecology Progress Series. 419:267-282
ISSN: 1616-1599
0171-8630
DOI: 10.3354/meps08860
Popis: During nesting periods, seabirds are known to exhibit considerable inter-annual vari- ability in diets, yet little is known about the diets of pelagic seabirds during non-breeding periods. Over 5 yr (2005 to 2009), we studied dietary partitioning between sympatric greater and sooty shear- waters, Puffinus gravis and P. griseus, during migratory staging periods in the Northwest Atlantic. Stable-isotope (SI; n = 253) and fatty-acid (FA; n = 127) signatures from blood samples were used to assess inter-annual patterns in diet and quantify prey choices. In addition to significant effects of year, capture site, and body condition, SI signatures revealed subtle, but consistent, dietary partition- ing between species. In all years, greater shearwaters fed at slightly higher trophic levels (overall mean δ 15 N = 13.6‰) and lower δ 13 C (-19.1‰) than sooty shearwaters (δ 15 N = 13.3‰, δ 13 C = -18.9‰). SI mixing models revealed that sooty shearwaters relied more heavily on euphausiids Meganyc- tiphanes norvegica, while greater shearwaters consumed more herring Clupea harengus, squid Illex illecebrosus, and, in some years, mackerel Scomber scombrus. In 2005/2006, bird diets consisted pri- marily of herring and krill, but demonstrated a shift towards krill and squid during 2007-2009. FA from bird plasma showed little inter-specific partitioning but a strong signal of annual variation for both species. We used a subset of prey FA and a modified multivariate approach to model bird diets and obtained dietary preferences broadly in agreement with SI results. The present study revealed inter-annual variability and dietary partitioning in sympatric species of pelagic seabirds, and high- lights potential shifts in prey availability to predators in the Bay of Fundy.
Databáze: OpenAIRE
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