The stress hormone corticosterone in a marine top predator reflects short-term changes in food availability
Barrett, Robert; Erikstad, Kjell E; Sandvik, Hanno; Myksvoll, Mari Skuggedal; Jenni-Eiermann, Susi; Kristensen, Ditte Lyngbo; Moum, Truls; Reiertsen, Tone; Vikebø, Frode Bendiksen
Journal article, Peer reviewed
Date
2015Metadata
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Abstract
In many seabird studies, single annual proxies of prey abundance have beenused to explain variability in breeding performance, but much more importantis probably the timing of prey availability relative to the breeding season whenenergy demand is at a maximum. Until now, intraseasonal variation in preyavailability has been difficult to quantify in seabirds. Using a state-of-the-artocean drift model of larval cod Gadus morhua, an important constituent of thediet of common guillemots Uria aalge in the southwestern Barents Sea, we wereable to show clear, short-term correlations between food availability and measurementsof the stress hormone corticosterone (CORT) in parental guillemotsover a 3-year period (2009–2011). The model allowed the extraction of abundanceand size of cod larvae with very high spatial (4 km) and temporal resolutions(1 day) and showed that cod larvae from adjacent northern spawninggrounds in Norway were always available near the guillemot breeding colonywhile those from more distant southerly spawning grounds were less frequent,but larger. The latter arrived in waves whose magnitude and timing, and thusoverlap with the guillemot breeding season, varied between years. CORT levelsin adult guillemots were lower in birds caught after a week with high frequenciesof southern cod larvae. This pattern was restricted to the two years (2009and 2010) in which southern larvae arrived before the end of the guillemotbreeding season. Any such pattern was masked in 2011 by already exceptionallyhigh numbers of cod larvae in the region throughout chick-rearing period. Thefindings suggest that CORT levels in breeding birds increase when the arrival ofsouthern sizable larvae does not match the period of peak energy requirementsduring breeding.Common guillemot, CORT, food availability,seabird, Uria aalge
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