Constraints on foraging and their consequences for emperor penguins
Emperor penguins are the largest living penguin and the only bird species that breeds during the Antarctic winter, on sea-ice around the Antarctic continent. They are fundamentally adapted to the high Antarctic sea-ice environment, showing radical breeding and foraging behaviour. High latitude-breed...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universität Bremen
2007
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| Online Access: | https://media.suub.uni-bremen.de/handle/elib/2420 https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000108416 |
| Summary: | Emperor penguins are the largest living penguin and the only bird species that breeds during the Antarctic winter, on sea-ice around the Antarctic continent. They are fundamentally adapted to the high Antarctic sea-ice environment, showing radical breeding and foraging behaviour. High latitude-breeding exposes emperor penguins to extreme changes in sea-ice cover and light conditions over the course of the year, both factors that are likely to affect foraging success. This thesis examines some of the ecological and physiological constraints on emperor penguin foraging behaviour using birds from Pointe GÃ ?Ã ©ologie, Antarctica and considers how these birds modulate behaviour to cope with their extraordinary environment. The trophic impact of emperor penguins on squid communities at Pointe Geologie was examined by analysing squid beaks obtained from the stomach of moribund chicks. Emperor penguins consumed primarily four squid species (Psychroteuthis glacialis, Kondakovia longimana, Gonatus antarcticus, Alluroteuthis antarcticus). Beak nitrogen stable isotope ratios indicated that squids consumed by the emperor penguin cover about two trophic levels. The trophic position of emperor penguins from different breeding colonies considerably differs because the principal components in the emperor penguin's diet; fish, krill and squid, differ in their average trophic level and also in their composition. The foraging areas and depths used by 20 breeding emperor penguins at Pointe GÃ ?Ã ©ologie during winter, spring and summer in 2005/2006 (corresponding to incubation, early chick-brooding, late chick-rearing and the adult pre-moult period, respectively) were investigated using satellite telemetry and pressure transducers. Chick-provisioning penguins foraged over the Antarctic shelf in areas covered by winter pack-ice, using fissures in the ice although winter-foraging females compensated for limited water access by expanding their horizontal search component underwater. During the spring ice break-up, foraging ranges ... |
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