birds and insects respond differently to combinations of semi-natural features in farm landscapes.
Abstract
Semi-natural features among farmland have a key role in maintaining wildlife in rural landscapes. Practical conservation requires knowledge of which combinations of features are of greatest value and whether this differs among faunal groups. We used a 'landscape' approach to investigate the relative importance to birds and insects (bees, flies, wasps) of combinations of three wooded features typical of farmland in south-eastern Australia: scattered trees, wooded roadsides and wooded streamside vegetation. We selected 44 landscapes (1 km diameter) representing four combinations: (a) landscapes with all three features present, (b) landscapes lacking scattered trees, (c) lacking wooded roadsides and (d) lacking wooded streamsides. We surveyed birds and selected insects, and compared mean alpha (α, site), beta (β, between site) and gamma (γ, landscape) diversity for each taxon between landscape types; and gamma (γ) diversity of bird species displaying breeding activity. Mean α-diversity of birds was reduced in landscapes lacking wooded roadsides or streams, relative to those with all three wooded features; while species differentiation (β-diversity) increased in these landscapes. Loss of streamside vegetation had the greatest landscape-scale impact, reducing γ-diversity by ~33% for all land-birds and ~50% for woodland birds. Bird breeding activity declined by ~50% in landscapes lacking wooded streamsides. In contrast, insects showed little response, except bees for which mean α-diversity was greater in more open landscapes lacking scattered trees or wooded roadsides, compared with those containing all wooded features. This did not lead to differences in landscape-level (γ) diversity. Synthesis and applications. Birds and insects respond differently to combinations of semi-natural features in rural landscapes, highlighting the need to better meet the requirements of multiple faunal groups in nature conservation activities. Wooded features, especially streamside vegetation, are critical for maintaining diversity and breeding activity of woodland birds. Given a general lack of knowledge of the insect fauna in some regions and varied results here, a prudent approach is to foster a diverse farmland mosaic comprising semi-natural habitats together with floristically rich, modified features that provide temporally dynamic resources. These combined landscape features are important for faunal conservation, while also supporting farm productivity and ecosystem services.