Citation: Barrett, R. T., K. E. Erikstad, H. Sandvik, M. S. Myksvoll, S. Jenni-Eiermann, D. L. Kristensen, T. Moum, T. K. Reiertsen, and F. Vikebø (2015) The stress hormone corticosterone in a marine top-predator reflects short-term changes in food availability. Ecology and Evolution, 5, 1306–1317.
doi: 10.1002/ece3.1438 [what’s a doi?].
Key words: CORT, fish larvae, Gadus morhua, match–mismatch, ocean drift model, Uria aalge.
Abstract:
In many seabird studies, single annual proxies of prey abundance have been used
to explain variability in breeding performance, but much more important is probably
the timing of prey availability relative to the breeding season when energy demand
is at a maximum. Until now, intraseasonal variation in prey availability has been
difficult to quantify in seabirds. Using a state-of-the-art ocean drift model of
larval cod Gadus morhua, an important constituent of the diet of common
guillemots Uria aalge in the southwestern Barents Sea, we were able to show
clear, short-term correlations between food availability and measurements of the
stress hormone corticosterone (CORT) in parental guillemots over a
3-year period (2009–2011). The model allowed the
extraction of abundance and size of cod larvae with very high spatial (4 km)
and temporal resolutions (1 day) and showed that cod larvae from adjacent
northern spawning grounds in Norway were always available near the guillemot
breeding colony while those from more distant southerly spawning grounds were less
frequent, but larger. The latter arrived in waves whose magnitude and timing, and
thus overlap with the guillemot breeding season, varied between years. CORT levels
in adult guillemots were lower in birds caught after a week with high frequencies
of southern cod larvae. This pattern was restricted to the two years (2009 and 2010)
in which southern larvae arrived before the end of the guillemot breeding season.
Any such pattern was masked in 2011 by already exceptionally high numbers of cod
larvae in the region throughout chick-rearing period. The findings suggest that
CORT levels in breeding birds increase when the arrival of southern sizable larvae
does not match the period of peak energy requirements during breeding.
Full text: © 2015 The Authors. If you accept (i) the conditions specified in the Creative Commons "Attribution" 4.0 licence, and (ii) that printouts have to be made on recycled paper, you may download the article here (pdf, 1.1 MB).
Supplementary material: The correlation matrix of explanatory variables and
the table over models explaining variation in baseline CORT levels of common guillemots are
available as Supporting Information (pdf, 46 kB).
Individual guillemot measurements and modelled cod larvae abundances are available
from the Dryad Digital Repository at
doi:10.5061/dryad.cb5h8
[what’s Dryad?].