Variable responses of seabirds to change in marine climate: California Current, 1985-1994

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 212:265-281 (2001) - doi:10.3354/meps212265 Variable responses of seabirds to change in marine climate: California Current, 1985-1994 Cornelia S. Oedekoven*, David G. Ainley, Larry B. Spear H. T. Harvey & Associates, 3150 Almaden Expwy, Suite 145, San Jose, California 95118, USA *Present address: Southwest Fisheries Science Center, La Jolla, California 92037-0271, USA. E-mail: coedekoven@yahoo.com ABSTRACT: We conducted annual ship-board surveys to determine the density and distribution of seabirds off central California in relation to marine climate, from 1985 to 1994. Summarized here are results for the sooty shearwater Puffinus griseus, the common murre Uria aalge, and Cassin¹s auklet Ptychoramphus aleuticus, the 3 most abundant seabirds in the central part of the California Current (91% of seabird abundance and biomass). During the study, sea-surface temperature, wind speed and thermocline depth all increased, salinity decreased and thermocline intensity (slope) showed no consistent trend. Periods of cool water and warm water, as well as offshore and inshore excursions of the shelfbreak front, alternated and were mediated by the Southern Oscillation and upwelling intensity. The responses to climate variation by the 3 seabird species were in accord with their respective morphologies and natural history patterns. All moved closer to shore and away from the shelf-break front (which also weakened). Abundance of the shallow-diving shearwater and auklet decreased dramatically, but those of the deeper-diving murre did not. The shearwater, which nests in the southern hemisphere and is the most mobile of the 3 seabirds, likely changed its migration routes and reduced its association with the California Current. The auklet, which breeds within the study area and lacks mobility, declined in number, most likely due to reduced breeding success and subsequent reduced population size. Remaining auklets moved away from the shelfbreak, but not as far inshore as the shearwater. The murre, which also breeds locally, is the most adaptable owing to its deeper-diving capabilities. It shifted distribution within the study area to feed on alternative prey found throughout the water column. KEY WORDS: Aleutian Low Pressure System · Cassin¹s auklet · Climate change · Common murre · El Niño · La Niña · Sooty shearwater · Upwelling Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 212. Online publication date: March 08, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.