Assessing the ecological impacts of non-native gamebird release on reptiles in the UK

背景和理由：英国长期以来一直将环颈雉（Phasianus colchicus）和红腿鹧鸪（Alectoris rufa）（以下称为“猎鸟”）释放到农村进行射击（Madden & Sage 2020）。自1960年以来，在射猎场释放的猎鸟数量一直在增加，1960年至2014年期间，每个地点释放的鸟类密度每年增加4.3% （Robertson等人，2017年），自2004年以来，鸟类数量增加了38% （Aebischer 2019年）。尽管如此，射击的猎鸟数量保持相对稳定，这导致了后释放效率的降低（Mason et al. 2020）。据最新估计，每年大规模放生的野禽数量为5700万只，超过了欧洲或北美任何其他野禽的放生数量（Mason et al. 2020）。在秋季放生时，据估计，野禽的生物量是英国所有本土繁殖鸟类春季生物量总和的两倍多（Blackburn and Gaston 2018; Aebischer 2019）。在英国释放的野禽数量越来越多，引发了环保主义者、政策制定者和射击社区本身对这种广泛活动的生态影响的担忧（Mason et al. 2020）。有证据表明，狩猎产业管理可以间接地有益于生物多样性，例如通过林地保护和维护（Oldfield et al. 2003）和树篱网络（Draycott et al. 2012）。然而，通过一系列直接压力（捕食、觅食、栖息地改变）和间接压力（对通才捕食者的影响、资源竞争、非法迫害和铅弹中毒），非本地猎禽的数量和密度正在产生广泛的负面生态影响。坊间证据表明，放生野鸟可能对英国爬行动物种群产生负面影响（Edgar et al. 2015; Gardner et al. 2019; Mason et al. 2020）。最近的评论建议进行紧急研究，检查游戏鸟对爬行动物的直接影响（Madden和Sage 2020； Mason等人2020），因为缺乏关于游戏鸟的影响及其对爬行动物种群的潜在有害影响的信息。在英国本土物种减少的背景下（Hayhow et al. 2019），了解大规模释放野禽的影响是一项重大挑战。因此，为猎禽和爬行动物之间的关系提供经验证据的研究是有充分理由的。

Background and Rationale:Britain has a long history of releasing ring-necked pheasant (Phasianus colchicus) and red-legged partridge (Alectoris rufa), hereafter referred to as "gamebirds", into the countryside for the shoot (Madden & Sage 2020). The number of gamebirds released on shooting estates has been increasing since 1960, with a 4.3% annual increase in the density of birds released per site between 1960 and 2014 (Robertson et al. 2017), and a 38% increase in the number of birds since 2004 (Aebischer 2019). Despite this, the numbers of gamebirds shot have remained relatively stable, which has led to a reduction in rear-releasing efficiency (Mason et al. 2020). At 57 million birds, this latest estimate for the annual large-scale release of gamebirds exceeds any other gamebird release in Europe or North America (Mason et al. 2020), and at the Autumn point of release it is estimated that gamebirds represent more than twice the spring biomass of all native UK breeding birds combined (Blackburn and Gaston 2018; Aebischer 2019).The increasing number of gamebirds released in the UK has triggered concerns about the ecological impacts of this widespread activity amongst conservationists, policymakers and within the shooting community itself (Mason et al. 2020). There is evidence that game estate management can indirectly benefit biodiversity, for example through woodland protection and maintenance (Oldfield et al. 2003) and on hedgerow networks (Draycott et al. 2012). However, concerns have been raised that the numbers and densities of non-native gamebirds are having widespread negative ecological impacts through a range of direct pressures (predation, browsing, habitat modification) and indirect pressures (impacts on generalist predators, resource competition, illegal persecution and lead ammunition poisoning).Anecdotal evidence suggests that gamebird release may be having a negative impact on UK reptile populations (Edgar et al. 2015; Gardner et al. 2019; Mason et al. 2020). Recent reviews recommend urgent research examining the direct impacts of gamebirds on reptiles (Madden and Sage 2020; Mason et al. 2020) as information is lacking on the effect of gamebirds and their potentially detrimental effects on reptile populations. Against a backdrop of native species decline in the UK (Hayhow et al. 2019), understanding the impacts of large-scale releases of gamebirds represents a major challenge. There is therefore strong justification for studies that aim to produce empirical evidence on the relationship between gamebirds and reptiles.