Diet of auklet chicks in the Aleutian Islands, Alaska: Similarity among islands, interspecies overlap, and relationships to ocean climate

Alexander L. Bond, Ian L. Jones, Jeffrey C. Williams, G. Vernon Byrd

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Seabirds are effective samplers of the marine environment, and can be used to measure resource partitioning among species and sites via food loads destined for chicks. We examined the composition, overlap, and relationships to changing climate and oceanography of 3,216 food loads from Least, Crested, and Whiskered Auklets (Aethia pusilla, A. cristatella, A. pygmaea) breeding in Alaska during 1994-2006. Meals comprised calanoid copepods (Neocalanus spp.) and euphausiids (Thysanoessa spp.) that reflect secondary marine productivity, with no difference among Buldir, Kiska, and Kasatochi islands across 585 km of the Aleutian Islands. Meals were very similar among species (mean Least-Crested Auklet overlap C = 0. 68; Least-Whiskered Auklet overlap C = 0. 96) and among sites, indicating limited partitioning of prey resources for auklets feeding chicks. The biomass of copepods and euphausiids in Least and Crested Auklet food loads was related negatively to the summer (June-July-August) North Pacific Gyre Oscillation, while in Whiskered Auklet food loads, this was negatively related to the winter (December-January-February) Pacific Decadal Oscillation, both of which track basin-wide sea-surface temperature (SST) anomalies. We found a significant quadratic relationship between the biomass of calanoid copepods in Least Auklet food loads at all three study sites and summer (June-July) SST, with maximal copepod biomass between 3-6°C (r 2 = 0. 71). Outside this temperature range, zooplankton becomes less available to auklets through delayed development. Overall, our results suggest that auklets are able to buffer climate-mediated bottom-up forcing of demographic parameters like productivity, as the composition of chick meals has remained constant over the course of our study.

Original languageEnglish
Pages (from-to)115-129
Number of pages15
JournalJournal of Ornithology
Volume153
Issue number1
DOIs
Publication statusPublished - 1 Jan 2012

Keywords

  • Aethia
  • Aleutian Islands
  • Auklet
  • Climate
  • Diet
  • Overlap

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