BTO - Breeding Birds of the Wider Countryside: Discussion 4.3

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4.3	Ten-year trends and evidence for species recovery
If the status of species that have shown long-term declines were now improving, we would expect to find more positive trends in recent years compared with the earlier part of the time series. To examine this we list here the best change estimates over the most recent ten-year period for which we have data (1995–2005) for all of the declining species listed in the previous section of this report (Table 4.3). The table also includes four species, Wood Warbler (amber listed), Red Grouse (amber listed), Grasshopper Warbler (red listed) and Snipe (amber listed) for which we are able to report 10-year trends but lack reliable data covering longer periods.


Note: Based on smoothed trends using data to 2006, but last year truncated as it is less reliable (see Methods).

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The 43 species listed include 17 from the red list, 18 declining species that are amber listed on account of population declines and eight species that are not formally listed as declining. Nine species, Dunnock, Whitethroat, Reed Bunting, Nightingale, Song Thrush, Red-legged Partridge, Goldcrest, Snipe, Tree Sparrow and Grey Wagtail, show clear positive trends over the last ten years. The increases in the red-listed Song Thrush and Reed Bunting are particularly encouraging, as are the positive trends for amber-listed Dunnock and Grey Wagtail. However, the most recent figures for Song Thrush and Grey Wagtail suggest that their recoveries may be levelling off well short of their previous population levels. Similarly while the BBS shows a 29% increase in Snipe over the last 10 years, the population has been declining again since 2003. Whitethroat numbers have increased steadily since the mid-1980s but are still far below the population level prior to the 1968/69 crash. The increase in Tree Sparrow numbers is very welcome but is coming from such a low level that numbers remain far below those of the mid-1970s, with the population trend graph still showing little sign of a clear recovery.

The rate of decline of 25% over 25 years that is used as a threshold for amber listing is equivalent to a decline of 10.9% over ten years (assuming both have the same annual rate of change). A further 10 species, Lapwing, Marsh Tit, Common Sandpiper, Meadow Pipit, Bullfinch, Lesser Whitethroat, Mistle Thrush, Kestrel, Grasshopper Warbler and House Martin have population changes of between +11% and -11% over the last 10 years. None of these changes are statistically significant and these populations are best regarded as stable. Thus our data suggest that the declines of these species appear to be levelling off, although there is as yet no clear indication of recovery.

Ten-year changes for the remaining 24 species in Table 4.3 indicate ongoing declines, with rates equivalent to at least 25% over 25 years. Five species, Willow Tit, Wood Warbler, Little Grebe, Turtle Dove and Lesser Spotted Woodpecker, have declined by more than 50% over the last ten years alone. The ongoing declines of so many of the species listed in Table 4.3 must be a cause of serious conservation concern.

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This report should be cited as: Baillie, S.R., Marchant, J.H., Crick, H.Q.P., Noble, D.G., Balmer, D.E., Barimore, C., Coombes, R.H., Downie, I.S., Freeman, S.N., Joys, A.C., Leech, D.I., Raven, M.J., Robinson, R.A. & Thewlis, R.M. (2007) Breeding Birds in the Wider Countryside: their conservation status 2007. BTO Research Report No. 487. BTO, Thetford. (http://www.bto.org/birdtrends) Pages maintained by Susan Waghorn and Iain Downie: Last updated 7 November, 2008