Landscape, cropping and field boundary influences on bird abundance

Abstract

Given likely dramatic land use changes in the UK, there is a need to predict their impact upon biodiversity. Such predictions require an understanding of the habitat factors that determine species’ abundances. We relate British farmland bird abundance at the 1 km square scale to three variable sets: landscape composition (for example, areas of woodland, urban and arable), field boundary characteristics and cropping. We then use multi‐model inference to summarize model fits for each variable set and compare their explanatory power to identify the relative importance of the three forms of description of the farm landscape. The important variables across species within each set show the habitat features that are most significant for the farmland bird community. Models comprising landscape variables provided the best fits for 21 of 31 bird species, while field boundary variables were most important for seven species and cropping variables for one. After controlling for landscape influences, we then found that field boundary variation was slightly more influential than cropping. These patterns remained when farmland‐specialist species were considered alone. This shows that landscapes are the most important determinant of bird abundance and that cropping patterns and field boundary characteristics are influential only within the constraints of landscape structure. However, boundaries and, especially, crops remain important from a management perspective because they are more volatile, and can still drive population change. Important single variables that affected multiple species included woodland (predominantly negative even within farmland‐dominated landscapes), hedges with trees (providing nesting habitat and song‐posts) and heterogeneity both of landscapes and of cropping (predominantly positive effects). The results indicate which habitat features offer the most scope for induced population changes via management action and potentially provide relationships for input into predictive models with respect to land‐use change.

Rural–urban gradient and land use in a millenary metropolis: how urbanization affects avian functional groups and the role of old villas in bird assemblage patterning

“…In fact, the study by Hostetler and Knowles-Yanez (2002) investigated the bird communities in a single town (Phoenix, Arizona, USA) and their results cannot be generalised. Since other recent papers have demonstrated the relationship between bird abundance and land use (Ortega-Álvarez and MacGregorFors, 2009;MacGregor-Fors et al, 2010;Suarez-Rubio et al, 2011;Siriwardena et al, 2012), our results contribute to the discovering of more generalizable patterns regarding the effect of land use on bird diversity.…”

A comparison of winter bird communities in agricultural grassland and cereal habitats in Ireland: implications for Common Agricultural Policy reform

“…In Ireland it appears that the proposed crop diversification measure under the CAP reforms would further exacerbate landscape homogenization and have a potentially serious negative effect on the farmland bird community because the interspersion of grassland and cereals is an important landscape feature for breeding and winter farmland birds (Robinson et al 2001, Gillings et al 2005. While there is a substantial amount of evidence that indicates the importance of habitat heterogeneity for protecting the integrity of farmland bird communities (McMahon et al 2008, Pickett & Siriwardena 2011, Siriwardena et al 2012, there are also strong indications that the species that have declined drastically over recent years are ground nesting species which require extensive homogeneous habitats (Bas et al 2009, Pickett & Siriwardena 2011. It must be emphasized that what is good for overall avian biodiversity may not be what is required for species of conservation concern.…”

The relative value of field survey and remote sensing for biodiversity assessment

“…Despite this, pragmatic trade‐offs result in a tendency for high‐resolution biodiversity‐habitat analyses to cover relatively small areas (Whittingham et al . ), while larger scale (hereafter meaning ‘spatial extent’) studies typically have lower resolution (Siriwardena, Cooke & Sutherland ; Rose et al . ).…”