Countryside vegetation provides supplementary habitat at the landscape scale for woodland birds in farm mosaics

Agricultural environments have a critical role in the global conservation of biodiversity, but the persistence of forest and woodland-dependent species in these systems is often limited by insufficient habitat. Modified or semi-natural 'countryside' (matrix) vegetation is used by many species, but its value at the landscape scale is rarely tested. Do such habitats simply provide additional resources for populations sustained by remnant native vegetation in the landscape, or can they enhance populations over and above that sustained by natural vegetation cover? We surveyed woodland-dependent birds in all types of landscape element in 27 farmland mosaics (100 ha each) in south-eastern Australia. Four measures of wooded vegetation cover were quantified: native vegetation only; and combinations of native vegetation plus scattered trees and/or tree plantations. We used an information-theoretic approach to compare the responses of 30 species to each measure of vegetation cover. Woodland birds were well represented in agricultural mosaics (65% of the regional species-pool); however, almost half were recorded only in mosaics with > 20% native vegetation cover. The incidence of 23 species was positively related to measures of wooded cover, indicating increased occurrence in mosaics with a greater cover of wooded vegetation. For 12 species, scattered trees and plantations provided supplementary habitat that enhanced their population status at the landscape scale, beyond that sustained by native vegetation cover. While native vegetation has a critical role for conservation in agricultural environments, careful management of wooded countryside elements (such as scattered trees, tree plantations) offers additional benefits to the woodland-dependent avifauna.