Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids

Abstract

We measured δ 15 N and δ 13 C values in the blood of breeding adults and nestlings of 5 species of alcids at Triangle Island, British Columbia, to estimate the extent to which these seabirds alter their foraging ecology across successive breeding stages. Considerable intraspecific (stage-tostage) and interspecific variation was found. Two species -common murre Uria aalge and pigeon guillemot Cepphus columba -fed consistently at high trophic levels (i.e. diets of fish) in inshore or benthically linked habitats. The foraging ecology of 3 others -Cassin's auklet Ptychoramphus aleuticus, rhinoceros auklet Cerorhinca monocerata and tufted puffin Fratercula cirrhata -was more variable. Tufted puffins exhibited especially dramatic trophic and habitat shifts between early and late-season diets. With the exception of tufted puffin, the diet of provisioning adults differed from that fed to their nestlings. Trophic level of the community as a whole increased as the season progressed due to the combination of trophic shifting by rhinoceros auklets and tufted puffins, and earlier breeding by zooplanktivorous Cassin's auklets than by piscivorous murres and guillemots. Our results contribute to a growing body of evidence that marine bird species exhibit considerable flexibility in their foraging behaviour and also shed new light on seasonal patterns in the trophic relations within marine bird communities.

Seabird year-round and historical feeding ecology: blood and feather δ13C and δ15N values document foraging plasticity of small sympatric petrels

“…Williams et al 2008, Davies et al 2009, and none, to our knowledge, has included histo rical samples from museum specimens in the analysis. Four main features emerge from our detailed isotopic investigation.…”

Seasonal shift in the foraging niche of Atlantic puffins Fratercula arctica revealed by stable isotope (δ15N and δ13C) analyses

“…These techniques are being increasingly used to examine seasonal shifts in trophic position of seabirds (e.g. Hedd & Montevecchi 2006, Williams et al 2008, Davies et al 2009) and to elucidate migration strategies and habitat preferences (foraging zones) during the non-breeding period (Cherel et al 2000, Quillfeldt et al 2005, Phillips et al 2009.…”

Long-term decline in egg size of Atlantic puffins Fratercula arctica is related to changes in forage fish stocks and climate conditions

“…Thus, even if herring is important, this strongly suggests that other prey played a larger role in determining the puffin egg size. Recent stable-isotope studies (Davies et al 2009, Hedd et al 2010 have suggested that Atlantic puffins and their sibling species tufted puffins Fratercula cirrhata prey on zooplankton in winter and the early breeding season. Furthermore, Sorensen et al (2009) showed that pre-breeding female Cassin's auklets Ptychoramphus aleuticus that fed on energetically superior copepods laid earlier and larger eggs than those that fed on poorer juvenile rockfish Sebastes spp.…”