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Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)

Dietary specialization, exploiting a small fraction of available food resources, is commonly reported for gulls and skuas. Predation of birds by these species is usually considered a specialist strategy employed by the minority of the population but non-specialists also predate birds and may actuall...

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Autores principales: Ingraham, Laura R., Oswald, Stephen A., Son, Eunice, Arnold, Jennifer M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7561145/
https://www.ncbi.nlm.nih.gov/pubmed/33057336
http://dx.doi.org/10.1371/journal.pone.0239180
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author Ingraham, Laura R.
Oswald, Stephen A.
Son, Eunice
Arnold, Jennifer M.
author_facet Ingraham, Laura R.
Oswald, Stephen A.
Son, Eunice
Arnold, Jennifer M.
author_sort Ingraham, Laura R.
collection PubMed
description Dietary specialization, exploiting a small fraction of available food resources, is commonly reported for gulls and skuas. Predation of birds by these species is usually considered a specialist strategy employed by the minority of the population but non-specialists also predate birds and may actually have a greater impact on the prey species. To date, most studies have focused on predatory bird-specialists, down-playing the possible importance of opportunistic predation by non-specialists. We addressed this by studying diet (regurgitated pellets and prey remains) and behavior of breeding Herring Gulls (Larus argentatus) over three summers at Gull Island, a mixed-species breeding colony in Lake Ontario. One-third of all pellets analyzed contained bird remains, primarily the most numerous breeding bird: Ring-billed Gull (L. delawarensis) chicks (51%) and adults (36%). Although all but one pair of Herring Gulls ate birds, all pairs maintained broad and mostly similar diets, with birds accounting for at most one-third of prey. Behavior also indicated that Herring Gulls at Gull Island were not predatory bird-specialists because predation was too infrequent to meet energetic requirements, was largely unsuccessful and was only ever observed when Ring-billed Gulls strayed into Herring Gull breeding territories. Instead, bird predation appeared mainly opportunistic, increasing with seasonal availability, access to shoreline, proximity to nesting Ring-billed Gulls and breeding territory size. Compared with predatory specialist Herring Gulls in the same region, individuals that predated birds at Gull Island did not display specialist behaviors and killed six times fewer birds (0.1–0.4 per day, on average) but were over 20 times more numerous (98% of the population versus 4%). Thus, our results indicate that opportunistic predation by non-specialists may have important consequences for prey species. Since opportunistic predation cannot be effectively managed using techniques widely advocated for specialist predators, it is essential to investigate cause of predation by large gulls prior to lethal management.
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spelling pubmed-75611452020-10-21 Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus) Ingraham, Laura R. Oswald, Stephen A. Son, Eunice Arnold, Jennifer M. PLoS One Research Article Dietary specialization, exploiting a small fraction of available food resources, is commonly reported for gulls and skuas. Predation of birds by these species is usually considered a specialist strategy employed by the minority of the population but non-specialists also predate birds and may actually have a greater impact on the prey species. To date, most studies have focused on predatory bird-specialists, down-playing the possible importance of opportunistic predation by non-specialists. We addressed this by studying diet (regurgitated pellets and prey remains) and behavior of breeding Herring Gulls (Larus argentatus) over three summers at Gull Island, a mixed-species breeding colony in Lake Ontario. One-third of all pellets analyzed contained bird remains, primarily the most numerous breeding bird: Ring-billed Gull (L. delawarensis) chicks (51%) and adults (36%). Although all but one pair of Herring Gulls ate birds, all pairs maintained broad and mostly similar diets, with birds accounting for at most one-third of prey. Behavior also indicated that Herring Gulls at Gull Island were not predatory bird-specialists because predation was too infrequent to meet energetic requirements, was largely unsuccessful and was only ever observed when Ring-billed Gulls strayed into Herring Gull breeding territories. Instead, bird predation appeared mainly opportunistic, increasing with seasonal availability, access to shoreline, proximity to nesting Ring-billed Gulls and breeding territory size. Compared with predatory specialist Herring Gulls in the same region, individuals that predated birds at Gull Island did not display specialist behaviors and killed six times fewer birds (0.1–0.4 per day, on average) but were over 20 times more numerous (98% of the population versus 4%). Thus, our results indicate that opportunistic predation by non-specialists may have important consequences for prey species. Since opportunistic predation cannot be effectively managed using techniques widely advocated for specialist predators, it is essential to investigate cause of predation by large gulls prior to lethal management. Public Library of Science 2020-10-15 /pmc/articles/PMC7561145/ /pubmed/33057336 http://dx.doi.org/10.1371/journal.pone.0239180 Text en © 2020 Ingraham et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Ingraham, Laura R.
Oswald, Stephen A.
Son, Eunice
Arnold, Jennifer M.
Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)
title Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)
title_full Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)
title_fullStr Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)
title_full_unstemmed Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)
title_short Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus)
title_sort opportunistic predation of birds by breeding herring gulls (larus argentatus)
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7561145/
https://www.ncbi.nlm.nih.gov/pubmed/33057336
http://dx.doi.org/10.1371/journal.pone.0239180
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