Bat activity in ephemeral stream-beds in the Pilliga forests: clarifying the importance of flyways and buffer widths in open forest and woodland
Bradley S. Law, Mark Chidel, Patrick Tap, 2011. "Bat activity in ephemeral stream-beds in the Pilliga forests: clarifying the importance of flyways and buffer widths in open forest and woodland", The Biology and Conservation of Australasian Bats, Bradley Law, Peggy Eby, Daniel Lunney, Lindy Lumsden
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Riparian zones provide significant habitat for microbats. In forests subject to logging, buffers are normally retained along stream-beds to maintain water quality and protect riparian vegetation and its associated fauna. We sampled bat activity as part of a broader program to assess biodiversity and to provide a scientific basis for determining buffer widths around ephemeral streams in the Pilliga State forests of north-west New South Wales. Anabat detectors recorded bat activity over two consecutive nights in one season at each of three dry stream-bed sizes (small, medium and large), clustered into five different locations (replicates). Anabat detectors were placed at varying distances perpendicular from the dry, stream-bed centre of ephemeral streams (0 m, 50 m, 100 m, 200 m). To assess the influence on bat activity of the flyway per se versus the riparian zone, one cluster of sites represented a control or reference that comprised dirt roads of three equivalent widths. Over the course of the study 22,967 bat calls were recorded from 15 species. A multivariate analysis of species composition indicated that there was no distinct bat assemblage characteristic of the riparian zone. Overall, bat activity was not influenced by stream-bed size or the perpendicular distance from the stream-bed. However, there was a significant interaction between distance and stream-bed size, with large stream-beds supporting three times more activity over the channels than adjacent forest and woodland. Similarly for reference sites, there was more activity directly over the road than adjacent woodland. The response of individual species to flyways on the different-sized stream-beds varied generally in accordance with predictions based on their ecomorphology and echolocation call type. We conclude that large flyways have the most biological importance to the activity of a range of bat species and that, in conjunction with studies on other components of biodiversity, the riparian zone rarely extends beyond the stream-bed channel in the Pilliga forests.