Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls
Studies of seabird diets may reveal subtle ways in which sympatric species partition resources to facilitate co-existence. We studied the variability and partitioning of diets between the Herring (Larus argentatus) and Great Black-backed Gulls (L. marinus), both generalist predators, during incubati...
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ftbioone:10.1525/cond.2011.110004 2023-07-30T04:04:49+02:00 Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls Rolanda J. Steenweg Robert A. Ronconi Marty L. Leonard Rolanda J. Steenweg Robert A. Ronconi Marty L. Leonard world 2011-11-01 text/HTML https://doi.org/10.1525/cond.2011.110004 en eng American Ornithological Society doi:10.1525/cond.2011.110004 All rights reserved. https://doi.org/10.1525/cond.2011.110004 Text 2011 ftbioone https://doi.org/10.1525/cond.2011.110004 2023-07-09T09:23:43Z Studies of seabird diets may reveal subtle ways in which sympatric species partition resources to facilitate co-existence. We studied the variability and partitioning of diets between the Herring (Larus argentatus) and Great Black-backed Gulls (L. marinus), both generalist predators, during incubation and early chick rearing on Kent Island, Bay of Fundy, Canada. We assessed diets from pellets collected around nests, regurgitates from captured birds, and stable-isotope analysis of prey items and tissues (blood and feathers) obtained from chicks and adults. Pellet analyses indicated that both species relied primarily on fish (28 to 45% of identified prey items) and crabs (15 to 43%). Stable-isotope analyses showed that the Great Black-backed Gull fed at a higher trophic level than the Herring Gull, both species fed at higher trophic levels during breeding than during nonbreeding, and both species has similar preferences for feeding inshore vs. offshore and in terrestrial vs. marine habitats. Contrary to previous research, we found that chicks were fed from a lower trophic level than where adults feed. Models of isotopic mixing estimating the proportion of assimilated diets were generally consistent with the pellet analysis for adults but revealed that both species fed their chicks more krill (>60%; Meganyctiphanes norvegica) and mackerel (>20%; Scomber scombrus) than adults consumed; adults may selectively provision their young with easily digestible prey and prey of high energy content. Our results reveal evidence of dietary partitioning between species and age classes, and highlight the strengths and biases associated with techniques for sampling gulls' diet. Text Meganyctiphanes norvegica BioOne Online Journals Canada Island Bay ENVELOPE(-109.085,-109.085,59.534,59.534) Kent Island ENVELOPE(70.133,70.133,-49.033,-49.033) The Condor 113 4 795 805 |
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BioOne Online Journals |
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ftbioone |
language |
English |
description |
Studies of seabird diets may reveal subtle ways in which sympatric species partition resources to facilitate co-existence. We studied the variability and partitioning of diets between the Herring (Larus argentatus) and Great Black-backed Gulls (L. marinus), both generalist predators, during incubation and early chick rearing on Kent Island, Bay of Fundy, Canada. We assessed diets from pellets collected around nests, regurgitates from captured birds, and stable-isotope analysis of prey items and tissues (blood and feathers) obtained from chicks and adults. Pellet analyses indicated that both species relied primarily on fish (28 to 45% of identified prey items) and crabs (15 to 43%). Stable-isotope analyses showed that the Great Black-backed Gull fed at a higher trophic level than the Herring Gull, both species fed at higher trophic levels during breeding than during nonbreeding, and both species has similar preferences for feeding inshore vs. offshore and in terrestrial vs. marine habitats. Contrary to previous research, we found that chicks were fed from a lower trophic level than where adults feed. Models of isotopic mixing estimating the proportion of assimilated diets were generally consistent with the pellet analysis for adults but revealed that both species fed their chicks more krill (>60%; Meganyctiphanes norvegica) and mackerel (>20%; Scomber scombrus) than adults consumed; adults may selectively provision their young with easily digestible prey and prey of high energy content. Our results reveal evidence of dietary partitioning between species and age classes, and highlight the strengths and biases associated with techniques for sampling gulls' diet. |
author2 |
Rolanda J. Steenweg Robert A. Ronconi Marty L. Leonard |
format |
Text |
author |
Rolanda J. Steenweg Robert A. Ronconi Marty L. Leonard |
spellingShingle |
Rolanda J. Steenweg Robert A. Ronconi Marty L. Leonard Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls |
author_facet |
Rolanda J. Steenweg Robert A. Ronconi Marty L. Leonard |
author_sort |
Rolanda J. Steenweg |
title |
Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls |
title_short |
Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls |
title_full |
Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls |
title_fullStr |
Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls |
title_full_unstemmed |
Seasonal and Age-Dependent Dietary Partitioning between the Great Black-Backed and Herring Gulls |
title_sort |
seasonal and age-dependent dietary partitioning between the great black-backed and herring gulls |
publisher |
American Ornithological Society |
publishDate |
2011 |
url |
https://doi.org/10.1525/cond.2011.110004 |
op_coverage |
world |
long_lat |
ENVELOPE(-109.085,-109.085,59.534,59.534) ENVELOPE(70.133,70.133,-49.033,-49.033) |
geographic |
Canada Island Bay Kent Island |
geographic_facet |
Canada Island Bay Kent Island |
genre |
Meganyctiphanes norvegica |
genre_facet |
Meganyctiphanes norvegica |
op_source |
https://doi.org/10.1525/cond.2011.110004 |
op_relation |
doi:10.1525/cond.2011.110004 |
op_rights |
All rights reserved. |
op_doi |
https://doi.org/10.1525/cond.2011.110004 |
container_title |
The Condor |
container_volume |
113 |
container_issue |
4 |
container_start_page |
795 |
op_container_end_page |
805 |
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1772816422699794432 |