Birds of prey as limiting factors of gamebird populations in Europe: a review

Authors

  • Jari Alkama,

    Corresponding author
    1. Ringing Centre, Finnish Museum of Natural History, FIN-00014 University of Helsinki, Finland
    2. Section of Ecology, Department of Biology, University of Turku, FIN-20014 Turku, Finland
      *Address for correspondence: Jari Valkama, Ringing Centre, Finnish Museum of Natural History, FIN-00014 University of Helsinki, Finland. Tel: +358 9 191 28849. Fax: +358 9 191 28843. E-mail: jari.valkama@helsinki.fi
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  • Erkki Korpimäki,

    1. Section of Ecology, Department of Biology, University of Turku, FIN-20014 Turku, Finland
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  • Beatriz Arroyo,

    1. Centre for Ecology and Hydrology, Banchory, Hill of Brathens, AB31 4BW, Scotland, UK
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  • Pedro Beja,

    1. ERENA, Ordenamento e Gestão de Recursos Naturais, Av. Visconde Valmor, 11-3, 1000–289 Lisboa, Portugal
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  • Vincent Bretagnolle,

    1. Centre d'Etudes Biologiques de Chizé (CEBC-CNRS), BP14, 79360 Villiers En Bois, France
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  • Elisabeth Bro,

    1. Office National de la Chasse et de la Faune Sauvage (ONCFS), Direction des Etudes et de la Recherche, 5, rue de Saint-Thibault, Boîte Postale 20, 78612 Le Perray en Yvelines cedex, France
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  • Robert Kenward,

    1. Centre for Ecology and Hydrology, Winfrith Technology Centre, Dorchester, Dorset, DT2 8ZD, UK
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  • Santi Mañosa,

    1. Departament de Biologia Animal, Universitat de Barcelona, Facultat de Biologia, Avinguda Diagonal 645, 08028-Barcelona, Spain
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  • Stephen M. Redpath,

    1. Centre for Ecology and Hydrology, Banchory, Hill of Brathens, AB31 4BW, Scotland, UK
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  • Simon Thirgood,

    1. Frankfurt Zoological Society, Africa Regional Office, PO Box 14935, Arusha, Tanzania
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  • Javier Viñuela

    1. Institute de Investigación en Recursos Cinegéticos (IREC), Ronda de Toledo s/n, 13005-Ciudad Real, Spain
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*Address for correspondence: Jari Valkama, Ringing Centre, Finnish Museum of Natural History, FIN-00014 University of Helsinki, Finland. Tel: +358 9 191 28849. Fax: +358 9 191 28843. E-mail: jari.valkama@helsinki.fi

ABSTRACT

Whether predators can limit their prey has been a topic of scientific debate for decades. Traditionally it was believed that predators take only wounded, sick, old or otherwise low-quality individuals, and thus have little impact on prey populations. However, there is increasing evidence that, at least under certain circumstances, vertebrate predators may indeed limit prey numbers. This potential role of predators as limiting factors of prey populations has created conflicts between predators and human hunters, because the hunters may see predators as competitors for the same resources. A particularly acute conflict has emerged over the past few decades between gamebird hunters and birds of prey in Europe. As a part of a European-wide research project, we reviewed literature on the relationships between birds of prey and gamebirds. We start by analysing available data on the diets of 52 European raptor and owl species. There are some 32 species, mostly specialist predators feeding on small mammals, small passerine birds or insects, which never or very rarely include game animals (e.g. hares, rabbits, gamebirds) in their diet. A second group (20 species) consists of medium-sized and large raptors which prey on game, but for which the proportion in the diet varies temporally and spatially. Only three raptor species can have rather large proportions of gamebirds in their diet, and another seven species may utilise gamebirds locally to a great extent. We point out that the percentage of a given prey species in the diet of an avian predator does not necessarily reflect the impact of that predator on densities of prey populations. Next, we summarise available data on the numerical responses of avian predators to changing gamebird numbers. In half of these studies, no numerical response was found, while in the remainder a response was detected such that either raptor density or breeding success increased with density of gamebirds. Data on the functional responses of raptors were scarce. Most studies of the interaction between raptors and gamebird populations give some estimate of the predation rate (per cent of prey population taken by predator), but less often do they evaluate the subsequent reduction in the pre-harvest population or the potential limiting effect on breeding numbers. The few existing studies indicate that, under certain conditions, raptor predation may limit gamebird populations and reduce gamebird harvests. However, the number and extent of such studies are too modest to draw firm conclusions. Furthermore, their geographical bias to northern Europe, where predator–prey communities are typically simpler than in the south, precludes extrapolation to more diverse southern European ecosystems. There is an urgent need to develop further studies, particularly in southern Europe, to determine the functional and numerical responses of raptors to gamebird populations in species and environments other than those already evaluated in existing studies. Furthermore, additional field experiments are needed in which raptor and possibly also mammalian predator numbers are manipulated on a sufficiently large spatial and temporal scale. Other aspects that have been little studied are the role of predation by the non-breeding part of the raptor population, or floaters, on the breeding success and survival of gamebirds, as well as the effect of intra-guild predation. Finally there is a need for further research on practical methods to reduce raptor predation on gamebirds and thus reduce conflict between raptor conservation and gamebird management.

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