The Shetland Bird Survey: Population trends for widespead breeding birds 2002-2019
Author(s): Hughes, R., O'Hanlon, N.J., Calladine, J. & Harvey, P.V.
Published: August 2021 Pages: 47pp
Journal: Bird Study/Ringing & Migration
Digital Identifier No. (DOI): 10.1080/00063657.2021.1955823
Population trends are estimated for the first time for twelve species based on Shetland Breeding Bird Survey data collected between 2002 and 2019.
To provide population trends for a selection of commoner breeding waders and passerines on the Shetland Isles, the most northerly region of the UK, which has historically been under-represented in national bird monitoring.
145 self-selected 1-km2 squares were surveyed between 2002 and 2019 using similar methods to the BTO/JNCC/RSPB Breeding Bird Survey (BBS), the main breeding bird monitoring scheme in the UK.
Over 17 years, Eurasian Oystercatcher Haematopus ostralegus, Northern Lapwing Vanellus vanellus and Common Redshank Tringa totanus declined whilst Eurasian Curlew Numenius arquata and Common Snipe Gallinago gallinago showed no significant trends. For passerines, Common Skylark Alauda arvensis and Northern Wheatear Oenanthe oenanthe declined, whilst Common Starling Sturnus vulgaris, Common Blackbird Turdus merula and House Sparrow Passer domesticus increased. Winter Wren Troglodytes troglodytes and Meadow Pipit Anthus pratensis showed no detectable changes. Comparisons with BBS trends for the UK and for Scotland are provided. For Eurasian Curlew, Common Starling and House Sparrow, trends were more favourable in Shetland than elsewhere in UK.
The Shetland Breeding Bird Survey provides useful trends of several bird species, which include important breeding numbers of Winter Wren and Common Starlings (both endemic subspecies), as well as nationally important wader populations. We recommend increasing the number of survey squares sampled each year, which would increase the precision of population trends produced from them. The inclusion of a random or stratified element to square selection would help to ensure that these trends are representative of the wider region.
The BTO/JNCC/RSPB Breeding Bird Survey (BBS) is a vital scheme for monitoring population trends of common and widespread species across the UK, with the data used for a wide-range of purposes, from providing an indication of the state of our environment to playing an important role in understanding the reasons behind changes in trends.
Data from BBS also highlights variation in the population trends of some species across different regions of the UK, for example Willow Warblers, which are faring relatively well in Scotland but have seen large declines in the south of England. Because BBS is designed to deliver robust and representative information at a broad geographical scale, the state of bird populations in a smaller region subject to its own drivers of change may require bespoke information such as more intensive local survey coverage.
To address the lack of enough data on common breeding birds across the isles, the Shetland Breeding Bird Survey (SBBS) was established in 2002 by the Shetland Biological Records Centre, part of Shetland Amenity Trust. Although the survey methods are comparable to BBS, in SBBS there are differences, including that 1-km squares are self-selected by the volunteer surveyors. In the 18 years since 2002, an impressive 145 1-km squares spread across the isles have been surveyed, allowing Shetland population trends for 12 common breeding passerine and wader species to be estimated for the first time.
SBBS data collected by volunteers between 2002 and 2019 has revealed that Oystercatcher, Lapwing and Redshank populations have declined at a similar rate to elsewhere in the UK. However, for Curlew no population change was detected in Shetland in contrast to the declines observed in this species in Scotland and the UK as a whole. Similarly, for passerines, declines of Skylark and Wheatear in Shetland were comparable to declines observed across the rest of the UK. However, there was better news for Starling and House Sparrow populations, which have both increased on the isles in contrast to declines at the UK level.
Thanks to SBBS volunteers, this improved understanding of local population changes can help enhance local conservation decisions and management on Shetland, as well as providing valuable information to better understand variation in population trends among different regions of the UK.
NotesWe thank Graham Fraser for advice on agriculture in Shetland and Mark Hancock for comments on earlier drafts. Thanks to all surveyors, notably those that have partaken for a number of years: Richard Ashbee, Geoff and Donna Atherton, Gary Bell, Geoff Blackman, Paul Bloomer, Nick Brett, Robbie Brookes, Juan Brown, Graham Bundy, Mark Chapman, Andy Cook, David Cooper, Dennis
Coutts, Wendy Dickson, Steve Duffield, Pat Dugard, Jon Dunn, Nick Dymond, Harry Edwards, Pete Ellis, Margaret Fiddy, Peter Flint, Dick Foyster, Paul Fisher, Rob Fray, Andy Freeman, Joyce Garden, Andy Gear, Sheila Gear, Beth & Tony Gerrard, Paul Goddard, Dave Hall, Phil Harris, Andrew Harrop, Derek Herning, Martin Heubeck, Sally Huband, John-Lowrie Irvine, Barbara Johnson, Carol Johnson, Logan Johnson, Laughton Johnston, Ray Johnston, Micky Maher, Brian Marshall, Karen Mackelvie, Mick Mellor, Will Miles, Steve Minton, Jim Nangle, Jim Nicolson, Rebecca Nason, Reinoud Norde, Kevin Osborn, Dave Okill, Mike Pennington, George Petrie, Jonathon Pinnick, Nathalie Pion, Dougie Preston, Ann Prior, Julie Redpath, Roger Riddington, Iain Robertson, Derek Rushton, Martin Schofield, Guy Smith, Simon Smith, Jenny Sutherland, Jonathan Swale, Roger Tait, Rory Tallack, Brydon Thomason, Howard Towll, Glen Tyler, John Uttley, Sue White, Kris Wilson, David Wood and various wardening staff from Fair Isle Bird Observatory, RSPB and SNH. We also thank the two reviewers for their constructive comments which improved the manuscript.
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