Pelagic habitat of seabirds in the eastern tropical Pacific: effects of foraging ecology on habitat selection

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 315:279-292 (2006) - doi:10.3354/meps315279 Pelagic habitat of seabirds in the eastern tropical Pacific: effects of foraging ecology on habitat selection L. Ignacio Vilchis1,2,*, Lisa T. Ballance2, Paul C. Fiedler2 1Integrative Oceanography Division, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, California 92093-0227, USA 2Ecosystem Studies Program, Southwest Fisheries Science Center, NOAA Fisheries, 8604 La Jolla Shores Drive, La Jolla, California 92037, USA *Email: lvilchis@ucsd.edu ABSTRACT: A central tenet of ecology is the quantification of species-habitat relationships in order to explain spatial variability in the distribution and abundance patterns of animals. We quantified habitat preferences for 6 tropical seabird species representing a phylogenetically and ecologically diverse group within the eastern tropical Pacific (ETP). Seabird censuses were conducted aboard NOAA research vessels from August to November of 1989 and 1990 using 300 m strip transect methods. Simultaneously with the seabird censuses and from the same ships, oceanic habitat was quantified by measuring sea surface temperature, salinity, and chlorophyll, as well as thermocline depth and strength. We quantified seabird habitat using generalized additive models fitted with forward and backward selection algorithms based on minimizing the Akaike information criterion (AIC). In general, seabird habitat models performed well in explaining spatial variability in abundance, reducing the null deviance to ranges between 42.8 and 73.5%, and predicting seabird density patterns with an accuracy ranging from 56.6 to 80.5%. Relative abundance of the species modeled affected the outcome: the higher the abundance, the more robust the fit. Seabirds feeding on fishes and squids associated with habitats characterized by deep (>100 m) and strong (>2°C 10 m–1) thermoclines, while planktivorous species preferred habitat characterized by shallower thermoclines with cooler surface temperatures (<25°C) and a less stratified water column. Thus, seabirds in different feeding guilds have clear and distinct habitat preferences within the ETP. We propose thermocline topography as a key variable in predicting distribution and abundance of seabirds in this area, probably due to its influence on the availability of seabird prey. KEY WORDS: Eastern tropical Pacific · Habitat relationships · Seabirds · Foraging ecology · Thermocline depth · Generalized additive models Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 315. Online publication date: June 13, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.