Impacts and management of common buzzards Buteo buteo at pheasant Phasianus colchicus release pens in the UK: a review
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) National Wildlife Management Centre, Animal & Plant Health Agency
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Sand Hutton, York YO41 1LZ
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UK
In the UK, alongside an expanding common buzzard population, there is increasing concern of raptor predation at pheasant release pens. Historically, losses of poults to raptor predation has been low, commonly (90 % of shoots) 1 % of birds released into pens, representing a small percentage of losses relative to all causes of mortality. A small number of shoots did suffer higher losses, estimated at >5 % at one in 30 estates and >10 % at some estates. Predation was lower (i) with increased poult age at release, (ii) in later releases, (iii) in pens with good vegetative cover, (iv) in pens within woods <50 acres and (v) in releases of <500 birds; there were also indications that predation was greater in high-density releases. Studies found no evidence for indirect losses (i.e. nonpredation impacts of raptor activity, e.g. panic-induced smothering events). Mitigation measures include the following: (i) sufficient vegetative cover (supplemented if necessary, e.g. brash piles), (ii) minimise perching opportunities for raptors, (iii) stock older poults, (iv) stock at recommended densities, (v) reflective tape and scaring devices and (vi) diversionary feeding. Significant gaps in knowledge were identified, including (i) predation being incompletely evaluated in the context of contemporary buzzard populations, (ii) indirect effects not adequately studied, (iii) occurrence of 'problem' individual buzzards is unclear, (iv) adequate field trials of mitigation measures are lacking and (v) level of gamekeepers' adherence to industry recommendations not known. Contemporary studies of these issues are necessary to understand the impacts and to inform management of buzzards at pheasant release pens.
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The potential role of predators, real or perceived, as limiting
factors of prey populations (Sih et al. 1985; Newton 1993,
1998) has created a number of human-wildlife conflicts
(Graham et al. 2005; Thirgood et al. 2005). Conflict occurs
where different groups of stakeholders disagree over the
management of a species and is frequently manifest in respect to
predator species whose populations are, or were formerly,
threatened, or are species considered to be charismatic or
iconic (Manosa 2002; Woodroffe et al. 2005). For birds of prey,
there are long-standing conflicts with gamebird, poultry and
other livestock interests, and more recently in respect to avian
species of conservation concern (JNCC 2000; Thompson et al.
2003; Valkama et al. 2005; Gibbons et al. 2007).
In most European regions, gamebird hunting is an
important socioeconomic activity in rural areas (Manosa 2002;
Vinuela and Arroyo 2002). Hunting may also be potentially
beneficial to biodiversity, by promoting conservation and
management of habitats within a strategy of conservation
through wise use of natural resources. However, in some
cases, there may be conflicts between hunting and the
conservation of biodiversity, which appears when hunting is
nonsustainable and intensive and, particularly, when predators
are subjected to illegal killing with the purpose of maximising
game numbers. Predators (including raptors) are perceived
within a large part of the hunting sector as an important
limiting factor for small game populations, and thus as an enemy
of hunters, in some cases leading to illegal control of protected
species. As a result of such illegal activities, the protectionist
movement sometimes perceives hunting as a detrimental
activity for conservation.
Conflict between the desire to maintain the economic and
conservation benefits of gamebird shooting and the legal
requirements and aesthetic appeal of conserving raptors is
manifest across Europe (Manosa 2002; Stroud 2003). In the UK,
during the nineteenth and twenteenth centuries, as a
consequence of persecution, egg-collection and organochlorine
pesticide poisoning, most raptor populations suffered dramatic
declines, with a number driven to extinction (JNCC 2000).
Subsequent recoveries of some species populations, through
reduced persecution, a ban on organochlorine pesticides and
protective wildlife legislation, are regarded as a major
conservation success (JNCC 2000; Greenwood et al. 2003). The
existence, however, of contemporary healthy and in some
cases abundant raptor populations, such as the buzzard, has
intensified conflict between conservationists and other
stakeholders that utilise prey species.
For wild avian prey, the existence of high levels of
predation may not be sufficient to demonstrate that predation is
imposing a detrimental impact at the population level
(Newton 1998; Park et al. 2005; Gibbons et al. 2007).
Predators may be taking similar numbers of birds that may
have died from other causes anyway (Errington 1956;
Newton 1993; Newton et al. 1997). In addition, many species
have evolved to cope with high levels of predation (Stoate and
Thomson 1999; Gibbons et al. 2007). For popu (...truncated)