Bailiwick Bat Survey: 2021 Report

Whiskered Bat by Jan Svetlik

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

Published: February 2022   Issue No.: 743

Publisher: British Trust for Ornithology Pages: 72pp

ISBN: 978-1-912642-34-2

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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 in 2021, the first season of the Bailiwick Bat Survey, including the first extensive baseline data for bats for the islands of Guernsey, Alderney, Herm and Sark. 


Working with a network of volunteers, static acoustic bat detectors were deployed over a long survey season, to provide the first extensive baseline data for bats for the islands of Guernsey, Alderney, Herm and Sark.  613 different locations across the Bailiwick of Guernsey were surveyed on 234 different nights, amounting to a total of 2,221 nights of recording effort across sites. Sound recordings were uploaded by volunteers to the BTO Acoustic Pipeline for analysis. The total recordings were found to include 710,260 bat recordings and 8,211 small terrestrial mammal recordings. Over 1.5 million recordings of bush-crickets and audible moth species were also recorded as ‘by-catch’. 

Following validation, the study confirmed the presence of 12 bat species, 5 small mammal species, 6 species of bush-crickets, and 2 audible moth species. This includes the first records of Serotine Eptesicus serotinus for Guernsey, Alderney and Herm, the first Leisler’s Bat Nyctalus leisleri, Common Noctule Nyctalus noctula, Lesser Horseshoe Bat Rhinolophus hipposideros and Whiskered or Brandt’s Bat Myotis mystacinus/brandtii for Guernsey, and potentially the first records of Grey Long- eared Bat Plecotus austriacus for the islands of Herm, Sark, Jethou and Lihou. More generally, we have a much 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 Alderney, Guernsey and Lihou, which represent the first records of Large Conehead for the Channel Islands.

Lastly, the project provides the first large-scale data on the distribution and activity of several species of small terrestrial mammals for the Bailiwick of Guernsey. 

The cover of BTO Research Report Bailiwick of Guernsey Bat Report
Staff Author(s)

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