However predator composition and behaviour differs between regions, and the majority of the research on edges effects on nest predation does not examine predator identities, suggesting a lack of general applicability of previous experiments findings to new environments \cite{THOMPSON_2007}.
Edge effects may have significant impacts for birds in the United Kingdom (U.K.). Native forest cover in the U.K. has been declining since the early Holocene, and the remaining areas are increasingly fragmented \cite{Whitehouse_2010}. Historical forest cover in the U.K. is inherently difficult to calculate, as land conversion from forest to subsistence farming has destroyed most of the native climax community and replaced it with artificial habitats, such as heath and moorland \cite{PAULEIT_2005}. From the 19th century onward, land use change globally has trended away from subsistence farming towards urbanisation.
Despite this trend, forest cover in the U.K. has actually been increasing since the 1920s \cite{defra2013}. Unfortunately, the majority of original forest cover has been replaced with non-native conifer monocultures, which does not provide the same ecological function as native forests and further fragments the U.K. deciduous climax community \cite{Liu_2018}. This high level of fragmentation is particularly problematic for the contained biological communities, as edge effects increase with as a function of habitat fragmentation \cite{Vetter_2013}. In addition, U.K. forest fragments often border open farming landscapes due to economic incentives for deforestation. These open landscapes provide a "hard" border to the forest, and are capable of supporting high densities of opportunistic generalist predators, which can then prey on the exposed edges \cite{Lahti_2001}. These risks are particularly high for ground nesting birds, given the predominantly terrestrial morphology of opportunistic generalist predators in the U.K.
Research on the effects of edge on nest predation in temperate ecotones have largely been performed in North America, which, given the role predator behaviour and bordering habitat play on predation rates suggest to lack applicability to U.K. deciduous woodland \cite{THOMPSON_2007}. This study aims to examine whether the previously hypothesised generality of edge effect mediated nest predation applies to a fragmented U.K. mixed deciduous woodland, at both ground and arboreal levels. It was hypothesised that predation rates would increase with proximity to the forest edge. Given the previous mixed effects of edge on nest predation, a large scale study seemed appropriate to examine the effect of nest predation in the deciduous climax community and this experiment is the first of its scale to study these effects in the U.K.
Many previous studies on nest predation using artificial nests have been unable to identify predators responsible for the predation, despite predator identity being hypothesised as a significant driver nest predation at forest edges \cite{article}. Therefore in this study, predators were identified, where possible, using bite marks left on plasticine eggs. This should provide insights into the composition of predators that prey on forest edges in deciduous woodland, and elucidate pest control priorities around these fragmented areas.
Methods