Although much of this report focuses on declines and their conservation significance, there are many species that are increasingly strongly as UK breeding birds.
In the current report, there are 19 species for which our most representative long-term trends show a statistically significant doubling in population size over periods of 20–46 years.
These are Mute Swan, Greylag Goose, Canada Goose, Shelduck, Mallard, Sparrowhawk, Buzzard, Coot, Stock Dove, Woodpigeon, Collared Dove, Green Woodpecker, Great Spotted Woodpecker, Magpie, Jackdaw, Carrion Crow, Great Tit, Blackcap and Nuthatch (taxonomic order).
The 19 species that have doubled over the long term are directly equivalent to the 29 that have halved in number over similar periods (see Declining species). The gap between these two totals has widened over recent years.
Six further species, monitored only over the18-year BBS period have also more than doubled. These are Gadwall, Little Egret, Red Kite, Barn Owl, Ring-necked Parakeet and Cetti's Warbler (see Increasing species). Three additional species have more than halved over this shorter period.
For ten species that are listed red or amber for population decline over the long term – Shelduck, Red Grouse, Tawny Owl, Wood Warbler, Willow Warbler, Garden Warbler, Grasshopper Warbler, Nightingale, House Sparrow, and Yellowhammer – decline has apparently started to level off, or has ceased, during the recent ten-year period. Signs of recovery noted last year for Corn Bunting are no longer evident, however. While indications are positive, wide confidence intervals for some of these species allow the possibility that severe decline is in fact continuing (see Ten-year trends and evidence of species recovery).
Six further formerly declining species – Whitethroat, Dunnock, Tree Sparrow, Bullfinch, Lesser Redpoll and Reed Bunting – have reversed their population trend to show significant increases over the last ten years. Whitethroat has already been moved to the green list (BoCC4). For all these species, however, population levels remain severely depleted, despite the recent increases.
This report should be cited as: Robinson, R.A., Marchant, J.H., Leech, D.I., Massimino, D., Sullivan, M.J.P., Eglington, S.M., Barimore, C., Dadam, D., Downie, I.S., Hammond, M.J., Harris, S.J., Noble, D.G., Walker, R.H. & Baillie, S.R. (2015) BirdTrends 2015: trends in numbers, breeding success and survival for UK breeding birds. Research Report 678. BTO, Thetford. www.bto.org/birdtrends