From cradle to early grave: juvenile mortality in European shags Phalacrocorax aristotelis results from inadequate development of foraging proficiency

Daunt, F. ORCID: https://orcid.org/0000-0003-4638-3388; Afanasyev, V.; Adam, A.; Croxall, J.P.; Wanless, S. ORCID: https://orcid.org/0000-0002-2788-4606. 2007 From cradle to early grave: juvenile mortality in European shags Phalacrocorax aristotelis results from inadequate development of foraging proficiency. Biology Letters, 3 (4). 371-374. 10.1098/rsbl.2007.0157

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Abstract/Summary

In most long-lived animal species, juveniles survive less well than adults. A potential mechanism is inferior foraging skills but longitudinal studies that follow the development of juvenile foraging are needed to test this. We used miniaturized activity loggers to record daily foraging times of juvenile and adult European shags Phalacrocorax aristotelis from fledging to the following spring. Juveniles became independent from their parents 40 days post-fledging. They compensated for poor foraging proficiency by foraging for approximately 3hd−1 longer than adults until constrained by day length in early November. Thereafter, juvenile foraging time tracked shortening day length up to the winter solstice, when foraging time of the two age classes converged and continued to track day length until early February. Few individuals died until midwinter and mortality peaked in January–February, with juvenile mortality (including some of the study birds) five times that of adults. In their last two weeks of life, juveniles showed a marked decline in foraging time consistent with individuals becoming moribund. Our results provide compelling evidence that juveniles compensate for poor foraging proficiency by increasing foraging time, a strategy that is limited by day length resulting in high winter mortality.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1098/rsbl.2007.0157
Programmes:	BAS Programmes > Other Special Projects CEH Programmes pre-2009 publications > Biodiversity
UKCEH and CEH Sections/Science Areas:	Watt
ISSN:	1744-9561
Format Availability:	Electronic, Print
Additional Keywords:	immature survival, foraging efficiency, environmental constraints, mortality, moribund
NORA Subject Terms:	Zoology Ecology and Environment
Date made live:	01 Aug 2007 13:46 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/669

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