MEPS 325:267-279 (2006)  -  doi:10.3354/meps325267

Assessing the nutritional stress hypothesis: relative influence of diet quantity and quality on seabird productivity

Patrick G. R. Jodice1,8,*, Daniel D. Roby1, Kathy R. Turco2, Robert M. Suryan3,4, David B. Irons4, John F. Piatt5, Michael T. Shultz5, David G. Roseneau6, Arthur B. Kettle6, Jill A. Anthony7

1US Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon 97331, USA
2Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99775, USA
3US Fish and Wildlife Service, Migratory Bird Management, 1011 East Tudor Road, Anchorage, Alaska 99503, USA
4US Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Hatfield Marine Science Center, Oregon State University, Newport, Oregon 97365, USA
5US Geological Survey, Alaska Science Center, 1011 East Tudor Road, Anchorage, Alaska 99503, USA
6US Fish and Wildlife Service, Alaska Maritime National Wildlife Refuge, Homer, Alaska 99603, USA
7Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
8Present address: US Geological Survey, South Carolina Cooperative Fish and Wildlife Research Unit, Clemson University, Clemson, South Carolina 29634, USA

ABSTRACT: Food availability comprises a complex interaction of factors that integrates abundance, taxonomic composition, accessibility, and quality of the prey base. The relationship between food availability and reproductive performance can be assessed via the nutritional stress (NSH) and junk-food (JFH) hypotheses. With respect to reproductive success, NSH posits that a deficiency in any of the aforementioned metrics can have a deleterious effect on a population via poor reproductive success. JFH, a component of NSH, posits specifically that it is a decline in the quality of food (i.e. energy density and lipid content) that leads to poor reproductive success. We assessed each in relation to reproductive success in a piscivorous seabird, the black-legged kittiwake Rissa tridactyla. We measured productivity, taxonomic composition, frequency, size, and quality of meals delivered to nestlings from 1996 to 1999 at 6 colonies in Alaska, USA, 3 each in Prince William Sound and Lower Cook Inlet. Productivity varied widely among colony-years. Pacific herring Clupea pallasi, sand lance Ammodytes hexapterus, and capelin Mallotus villosus comprised ca. 80% of the diet among colony-years, and each was characterized by relatively high energy density. Diet quality for kittiwakes in this region therefore remained uniformly high during this study. Meal delivery rate and meal size were quite variable among colony-years, however, and best explained the variability in productivity. Parent kittiwakes appeared to select prey that were energy dense and that maximized the biomass provisioned to broods. While these results fail to support JFH, they do provide substantial support for NSH.

KEY WORDS: Nutritional stress hypothesis · Junk-food hypothesis · Black-legged kittiwake · Diet · Provisioning rate · Productivity · Alaska

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