Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey

Abstract

Listen

Translate article

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 366:245-258 (2008) - DOI: https://doi.org/10.3354/meps07529 Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey Robert A. Ronconi*, Alan E. Burger Department of Biology, University of Victoria, PO Box 3020, Stn CSC, Victoria, British Columbia V8W 3N5, Canada *Email: rronconi@uvic.ca ABSTRACT: Flexibility in activity time budgets allows animals to cope with heterogeneous and changing environments. Many marine predators, such as seabirds, exhibit flexibility in their foraging behaviour to buffer reproductive success against periods of low prey availability. Over 3 years, 2004 to 2006, we studied the foraging behaviour of a threatened seabird, the marbled murrelet Brachyramphus marmoratus in southwestern Vancouver Island, British Columbia, Canada. An information–theoretic approach was used to compare among factors (temporal, spatial, environmental, and competitors) that may influence diving activity. We also quantified local prey availability by hydroacoustic surveys and regional oceanographic conditions (chlorophyll a concentrations and upwelling indices) to investigate relationships between diving activity, food supply and environmental conditions. Prey indices varied spatially, seasonally, and annually, showing reduced prey availability during incubation and chick-rearing of 2005. Upwelling indices and chlorophyll a concentrations, as an index of primary productivity, were delayed in 2005. Year and breeding phase had the greatest impact on diving activity, with additional variation among sites. Murrelets increased diving activity in years and seasons with scarce prey and poor oceanographic conditions (incubation and chick-rearing 2005) and decreased diving activity at sites with high prey availability. There was a linear relationship between diving activity and food availability, suggesting no clear thresholds in response to decreases in prey. Despite their flexible activity budgets, increased foraging effort by murrelets in 2005 was inadequate to ensure average levels of reproductive success. Thus, flexible foraging behaviour by murrelets may be ineffective to buffer reproductive success when environmental conditions are extremely poor. KEY WORDS: Activity budgets · Prey availability · Foraging ecology · Thresholds · Seabirds · Brachyramphus marmoratus Full text in pdf format PreviousNextCite this article as: Ronconi RA, Burger AE (2008) Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey. Mar Ecol Prog Ser 366:245-258. https://doi.org/10.3354/meps07529 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 366. Online publication date: August 29, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.