Birds and insects respond differently to combinations of semi-natural features in farm landscapes
Hall, Mark; Nimmo, Dale; Bennett, Andrew F (2022), Birds and insects respond differently to combinations of semi-natural features in farm landscapes, Dryad, Dataset, https://doi.org/10.5061/dryad.44j0zpch9
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. Marked differences in how birds and insects respond to different combinations of semi-natural features mean that a ‘one size fits all’ approach to nature conservation is insufficient. Wooded features, especially streamside vegetation, are critical for maintaining diversity and breeding activity of woodland birds. In the absence of adequate knowledge of many insect groups in southern Australia, 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. Small semi-natural features have disproportionate value for conservation, relative to their area, while also benefitting farm productivity and supporting ecosystem services.
Point counts for birds
Birds were surveyed at each site (n=12) in each landscape (n=44) using a 5-min point count. All birds detected visually or aurally within 20 m from the survey point were recorded. Surveys were conducted four times at each site; twice in spring 2014, once during autumn/winter 2015 and once in spring 2015, by the same observer (MH). Each site was surveyed once in each of four time periods (early morning, mid-morning, mid-afternoon, late afternoon).
Breeding records for birds
We recorded breeding activity, both while undertaking surveys and while walking between points within the landscape. A final systematic search (2 hours) of the entire landscape was conducted in spring 2015. Each observation of a breeding activity was assigned to one of 13 behaviours, scored according to the strength of evidence to indicate breeding success.
Three groups of insects (bees, flies and wasps) were sampled at each site (n=8) within each landscape (n=24). Vane traps (SpringStar Inc., Woodinville, Washington) were hung from a tree branch or pole at ~2 m height. A single vane trap per site (blue traps only) was deployed for one week between October 2014 and January 2015 (austral spring and summer); and two vane traps per site (one blue, one yellow) again for one week between October and November 2015 (spring). No pheromones, liquids or killing agents were used in traps. Species-level identification of bees was conducted by MH and an expert taxonomist (see Hall, 2018). Flies and wasps were identified to the highest taxonomic level possible (see Hall & Reboud, 2019). Individuals not categorically identified to species were assigned a name based on the nearest congener (using the prefix cf before species name), or were considered morphospecies.
All raw data are presented for each group in Excel spreadsheets (each group a separate tab).
Microsoft Excel or comparable software is required for opening the dataset.
Holsworth Wildlife Research Endowment
Rotary Club of Balwyn