In order to estimate the size of the challenge of restoring numbers of Common Swifts Apus apus to ‘historical levels’, it would be useful to know how many pairs have actually been lost. The rate of the decline is rather straightforward to work out – since 1994, the BTO/JNCC/RSPB Breeding Bird Survey (BBS; www.bto.org/our-science/projects/breeding-bird-survey/bbs-publications/bbs-reports) has provided an annual population index – but working out the numbers of birds lost requires a knowledge of how many pairs were breeding in Britain when records first began. Then, we can use these figures and the BBS population index to calculate the number of birds lost in between.
Are we underestimating the UK Common Swift population?
2024 Vol.117: Pages 114–119
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