Bailiwick Bat Survey 2022 Report

Author(s): Newson, S.E., Allez, S.L., Coule, E.K., Guille, A.W., Henney, J.M., Higgins, L., McLellan, G.D., Simmons, M.C., Sweet, E., Whitelegg, D. & Atkinson, P.W.

Published: January 2023 Issue No.: 750

Publisher: British Trust for Ornithology Pages: 90pp

ISBN: 978-1-912642-45-8

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This report presents the main findings from survey work delivered using passive acoustic monitoring devices deployed across the Bailiwick of Guernsey. Through the surveys that we support we aim to improve knowledge and understanding of species distribution and activity, covering a range of taxonomic groups, including bats, small terrestrial mammals and insects. Through this approach we provide robust datasets that can be used to inform better decision-making processes.

Abstract

Background Working with a network of fieldworkers, static acoustic bat detectors were deployed over a 7-month survey season, to provide a second year of baseline data for bats for Guernsey, Alderney, Herm and Sark. This report provides an overview of the survey coverage and main results from 2022.

Coverage During 2022, 622 different locations across the Bailiwick of Guernsey were surveyed. Recording was undertaken on 209 different nights mainly between April and the end of October, amounting to a total of 2,416 nights of recording effort across sites. Sound recordings (wav files) were uploaded by volunteers to the BTO Acoustic Pipeline, where a first automated analysis was carried out and provisional results returned. Recordings were then moved to deep glacial storage for later auditing. At the end of the survey season, a copy of the recordings was pulled back, and manual auditing of the results / recordings carried out.

Results Overall, 3,389,138 recordings were collected which, following analyses and validation, were found to include 872,126 bat recordings, and 8,587 small terrestrial mammal recordings. Over 2 million recordings of bush-crickets and audible moth species were also recorded as ‘by-catch’, for which we report species presence on a site and night basis. Following validation, the study confirmed the presence of 13 bat species, 5 small mammal species, 5 species of bush-crickets, and 2 audible moth species. This includes the first records of Serotine Eptesicus serotinus for Jethou, the first Leisler’s Bat Nyctalus leisleri for Herm, and the first Common Noctule Nyctalus noctula for Alderney. More generally, we have a better understanding now of the status of all species of bats across the Bailiwick of Guernsey, and of the relative importance of different areas. In addition, the bush-cricket Large Conehead Ruspolia nitidula was recorded for the first time on Herm, with records from two new locations on Guernsey, which follows the first records for Alderney, Guernsey and Lihou in 2021. Lastly, the project provides the first large-scale data on the distribution activity of several species of small terrestrial mammals for the Bailiwick of Guernsey. The report includes a full species-by-species breakdown of spatial, seasonal, and through-the-night patterns of activity.