In the current report, there are 28 species for which our best long-term trends show statistically significant population declines of greater than 50% over periods of 32–50 years (see Latest long-term alerts).
These are Little Grebe, Grey Partridge, Lapwing, Redshank, Woodcock, Snipe, Turtle Dove, Cuckoo, Little Owl, Willow Tit, Marsh Tit, Skylark, House Martin, Willow Warbler, Whitethroat, Starling, Mistle Thrush, Spotted Flycatcher, Nightingale, House Sparrow, Tree Sparrow, Yellow Wagtail, Tree Pipit, Greenfinch, Linnet, Lesser Redpoll, Yellowhammer and Corn Bunting (taxonomic order).
Little Grebe and House Martin have been added to this list in the current report as the declines are again statistically significant; both species previously raised a formal alert in BirdTrends 2017 report but did not do so last year due to the wide confidence intervals around the estimates.
One further species shows a non-significant decline greater than 50% over a long timescale. Change for Lesser Spotted Woodpecker is non-significant over the longest period but only because data are sparse and monitoring ceased in 1999; a further strong decline has since been logged by Atlas data.
The steepest long-term populations declines we have measured are for Turtle Dove, Tree Sparrow, Nightingale, Willow Tit and Grey Partridge, which have all declined by 90% or more since 1967, as, almost certainly, has Lesser Spotted Woodpecker. Turtle Dove shows the biggest decline of any species in this report (98%) and its rate of decline suggests it may soon disappear as a British breeding bird.
These 28 species that have halved in population size outweigh the 20 species found to show an equivalent increase, i.e. a doubling of population size, over similar periods. The gap between the numbers of species halving and doubling over the long-term has increased by five species in this year's report. Unusual weather conditions caused decreases for many species in 2018 (the "Beast from the East" and strong adverse winds affecting summer migrants) (Harris et al. 2019), and several species close to the boundaries have changed category. These changes are likely to be temporary and the gap is expected to reduce again in future years assuming that such unusual conditions do not become more frequent.
Except for Little Owl, which as an introduced species is not eligible, and Whitethroat, which has shown sustained, though still limited, recovery following considerable losses in the late 1960s, all but one of these rapidly declining species already benefit from listing as either red or amber Birds of Conservation Concern (PSoB/BoCC4). The other exception is the green-listed Greenfinch, which raises a high alert after a rapid decline in the last ten years, following a period of sustained population increases during the 1980s and 1990s.
Four species listed as amber after the 2015 review (BoCC4) arguably meet red-list criteria for breeding population decline: these are Snipe, Redshank, House Martin and Willow Warbler.
A further nine species raise lower-level concern, as a result of statistically significant long-term declines of between 25% and 50%. These are Common Sandpiper, Tawny Owl, Sedge Warbler, Garden Warbler, Song Thrush, Dunnock, Grey Wagtail, Meadow Pipit and Bullfinch. These species are already on the amber list on account of their population declines, except for Song Thrush and Grey Wagtail which are red listed, and Sedge Warbler and Garden Warbler which for now both remain on the green list. Populations Common Sandpiper and Tawny Owl have been in recent decline, whereas the more sustained recent increases by Song Thrush, Dunnock and Bullfinch have been insufficient to fully reverse earlier declines. Numbers of Sedge Warbler, Garden Warbler, Grey Wagtail and Meadow Pipit have fluctuated recently.
In addition, Curlew (now red listed) has declined by more than 25% (as also shown by atlas data), but raises no formal long-term alert because the confidence intervals around its change estimates are too wide.
Three species with much shorter monitoring histories have also decreased by more than half during just a 22-year period. Two of these are already red listed (Wood Warbler and Whinchat), and the third is currently amber listed (Swift). Set against these three species are seven that have more than doubled over equivalent shorter periods (see Positive changes). In addition, Wheatear, which has a shorter monitoring history, declined by between 25% and 50% over a 22-year period. This species is currently green-listed and shows a fluctuating trend over this period, although the last eight years have all seen negative changes.
Many of the declining species are farmland and woodland specialists, and some of the alerts may therefore relate to common pressures in these habitats which are reflected in the negative trends for both habitats in the UK Biodiversity Indicators, although some species may be subject to more specific issues which are detailed in the species accounts, for example the Greenfinch decline has been linked to trichomonasis disease. Four species commonly associated with urban habitats (Swift, House Martin, Starling and House Sparrow) have also been affected by the declines
This report should be cited as: Woodward, I.D., Massimino, D., Hammond, M.J., Harris, S.J., Leech, D.I., Noble, D.G., Walker, R.H., Barimore, C., Dadam, D., Eglington, S.M., Marchant, J.H., Sullivan, M.J.P., Baillie, S.R. & Robinson, R.A. (2019) BirdTrends 2019: trends in numbers, breeding success and survival for UK breeding birds. BTO Research Report 722. BTO, Thetford. www.bto.org/birdtrends
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