In the current report, there are 26 species for which our best long-term trends show statistically significant population declines of greater than 50% over periods of 31–49 years (see Latest long-term alerts).
These are Grey Partridge, Lapwing, Redshank, Woodcock, Snipe, Turtle Dove, Cuckoo, Little Owl, Willow Tit, Marsh Tit, Skylark, 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, House Martin, Song Thrush were also included on this list in the 2017 report. The long-term decline for Song Thrush is now just below the 50% threshold following four years of positive annual changes. The estimated declines for the other two species remain above 50%, but they no longer raise a formal alert 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, Grey Partridge, Nightingale and Willow Tit, 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 26 species that have halved in population size outweigh the 23 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 narrowed by three species in this year's report.
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 for the first time in the current report after a rapid decline in the last ten years, following a period of sustained population increases during the 1980s and 1990s.
A further seven species raise lower-level concern, as a result of statistically significant long-term declines of between 25% and 50%. These are Common Sandpiper, Sedge 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 which for now remains on the green list. Populations of the first two of these species have fluctuated with little overall trend in recent decades.
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 21-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 21-year period. This species is currently green-listed and shows a fluctuating trend over this period.
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. (2018) BirdTrends 2018: trends in numbers, breeding success and survival for UK breeding birds. Research Report 708. BTO, Thetford. www.bto.org/birdtrends