Food-limitation in a generalist predator
Investigating food-limitation in generalist predators is difficult, because they can switch to alternative prey, when one of their staple prey becomes scarce. Apart from data on the dynamics of the predator population, a robust study requires: (i) a documentation of the predator's entire prey b...
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ftunstandrewcris:oai:risweb.st-andrews.ac.uk:publications/2b52873d-e05f-44ce-8bfa-5bd63e72e1af 2023-05-15T13:00:24+02:00 Food-limitation in a generalist predator Rutz, Christian Bijlsma, Rob G. 2006-08-22 https://risweb.st-andrews.ac.uk/portal/en/researchoutput/foodlimitation-in-a-generalist-predator(2b52873d-e05f-44ce-8bfa-5bd63e72e1af).html eng eng info:eu-repo/semantics/restrictedAccess Rutz , C & Bijlsma , R G 2006 , ' Food-limitation in a generalist predator ' , Proceedings of the Royal Society B: Biological Sciences , vol. 273 , no. 1597 , pp. 2069-2076 . Accipiter gentilis avian population limitation floaters foraging ecology intra-guild predation northern goshawk GOSHAWKS ACCIPITER-GENTILIS BUZZARDS BUTEO-BUTEO GREAT HORNED OWLS ENVIRONMENTAL STOCHASTICITY NONTERRITORIAL FLOATERS PREY POPULATIONS SURVIVAL DIET MOVEMENTS article 2006 ftunstandrewcris 2021-12-26T14:23:36Z Investigating food-limitation in generalist predators is difficult, because they can switch to alternative prey, when one of their staple prey becomes scarce. Apart from data on the dynamics of the predator population, a robust study requires: (i) a documentation of the predator's entire prey base; and (ii) an experimental or natural situation, where profitable dietary shifts are impossible, because several preferred prey species decline simultaneously. Here, we provide a detailed description of how food-supply has limited a generalist avian top predator, the northern goshawk Accipiter gentilis. In our study area, populations of several principal goshawk prey species crashed simultaneously during 1975-2000, whereas other extrinsic factors remained essentially unchanged. The breeding and non-breeding segments of the local goshawk population declined markedly, associated with a significant increase in nest failures. Brood size of successful pairs remained unaffected by changes in prey availability. Breeding recruitment ceased at a time when potential replacement birds ('floaters') were still present, providing a rare empirical demonstration of an 'acceptance threshold' in raptor territory choice. To investigate how goshawk diet changed in response to varying food-supplies, we make novel use of an analytical tool from biodiversity research-'abundance-biomass-comparison curves' (ABC curves). With increasing levels of food-stress, the dominance of principal prey species in the diet decreased, and the number of small-bodied prey species increased, as did intra-guild predation. Our finding that breeder and non-breeder segments declined in concert is unexpected. Our results carry the management implication that, in food-limited raptor populations, externally induced breeder mortality can rapidly depress population size, as losses are no longer buffered when floaters reject breeding opportunities. Article in Journal/Newspaper Accipiter gentilis Northern Goshawk University of St Andrews: Research Portal |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
Accipiter gentilis avian population limitation floaters foraging ecology intra-guild predation northern goshawk GOSHAWKS ACCIPITER-GENTILIS BUZZARDS BUTEO-BUTEO GREAT HORNED OWLS ENVIRONMENTAL STOCHASTICITY NONTERRITORIAL FLOATERS PREY POPULATIONS SURVIVAL DIET MOVEMENTS |
spellingShingle |
Accipiter gentilis avian population limitation floaters foraging ecology intra-guild predation northern goshawk GOSHAWKS ACCIPITER-GENTILIS BUZZARDS BUTEO-BUTEO GREAT HORNED OWLS ENVIRONMENTAL STOCHASTICITY NONTERRITORIAL FLOATERS PREY POPULATIONS SURVIVAL DIET MOVEMENTS Rutz, Christian Bijlsma, Rob G. Food-limitation in a generalist predator |
topic_facet |
Accipiter gentilis avian population limitation floaters foraging ecology intra-guild predation northern goshawk GOSHAWKS ACCIPITER-GENTILIS BUZZARDS BUTEO-BUTEO GREAT HORNED OWLS ENVIRONMENTAL STOCHASTICITY NONTERRITORIAL FLOATERS PREY POPULATIONS SURVIVAL DIET MOVEMENTS |
description |
Investigating food-limitation in generalist predators is difficult, because they can switch to alternative prey, when one of their staple prey becomes scarce. Apart from data on the dynamics of the predator population, a robust study requires: (i) a documentation of the predator's entire prey base; and (ii) an experimental or natural situation, where profitable dietary shifts are impossible, because several preferred prey species decline simultaneously. Here, we provide a detailed description of how food-supply has limited a generalist avian top predator, the northern goshawk Accipiter gentilis. In our study area, populations of several principal goshawk prey species crashed simultaneously during 1975-2000, whereas other extrinsic factors remained essentially unchanged. The breeding and non-breeding segments of the local goshawk population declined markedly, associated with a significant increase in nest failures. Brood size of successful pairs remained unaffected by changes in prey availability. Breeding recruitment ceased at a time when potential replacement birds ('floaters') were still present, providing a rare empirical demonstration of an 'acceptance threshold' in raptor territory choice. To investigate how goshawk diet changed in response to varying food-supplies, we make novel use of an analytical tool from biodiversity research-'abundance-biomass-comparison curves' (ABC curves). With increasing levels of food-stress, the dominance of principal prey species in the diet decreased, and the number of small-bodied prey species increased, as did intra-guild predation. Our finding that breeder and non-breeder segments declined in concert is unexpected. Our results carry the management implication that, in food-limited raptor populations, externally induced breeder mortality can rapidly depress population size, as losses are no longer buffered when floaters reject breeding opportunities. |
format |
Article in Journal/Newspaper |
author |
Rutz, Christian Bijlsma, Rob G. |
author_facet |
Rutz, Christian Bijlsma, Rob G. |
author_sort |
Rutz, Christian |
title |
Food-limitation in a generalist predator |
title_short |
Food-limitation in a generalist predator |
title_full |
Food-limitation in a generalist predator |
title_fullStr |
Food-limitation in a generalist predator |
title_full_unstemmed |
Food-limitation in a generalist predator |
title_sort |
food-limitation in a generalist predator |
publishDate |
2006 |
url |
https://risweb.st-andrews.ac.uk/portal/en/researchoutput/foodlimitation-in-a-generalist-predator(2b52873d-e05f-44ce-8bfa-5bd63e72e1af).html |
genre |
Accipiter gentilis Northern Goshawk |
genre_facet |
Accipiter gentilis Northern Goshawk |
op_source |
Rutz , C & Bijlsma , R G 2006 , ' Food-limitation in a generalist predator ' , Proceedings of the Royal Society B: Biological Sciences , vol. 273 , no. 1597 , pp. 2069-2076 . |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766249661556850688 |