There has been plenty of work on the effect that climate change might have on the range of particular bird species; for example, Dartford Warbler is predicted to extend its range north with an increase in temperature. However, for the first time, scientists at the British Trust for Ornithology have looked at what effect climate change might have on the distribution and abundance on particular species. Four species were chosen; two with a southerly distribution, Nuthatch and Green Woodpecker, and two with a more northerly distribution, Meadow Pipit and Curlew. Future climate change was projected to result in population declines and range contractions northwards for both northerly distributed species (Figs 1 & 2). Declines for Eurasian Curlew were projected to be particularly severe, with national abundance under a high climate change scenario projected to be 34% lower in 2050 than the 1997 baseline, and 66% lower by 2080, a statistically significant drop. Modelled abundance in 1997 and 2080 under a high emissions scenario for Eurasian curlew In contrast, the two southerly species were projected to have population increases as a result of climate change. Green Woodpecker populations may increase substantially by 2050 and populations of Nuthatch to a lesser degree. The analytical methods used provide an important framework to make projections of impacts of climate change on species abundance, rather than simply projected range changes. Given the recent classification of Eurasian Curlew as globally near-threatened, these projections of continued population decline in Great Britain, where a significant proportion of the global population is held, and where declines are already occurring are of particular concern and highlight the likely long-term vulnerability of this species. The long-term protection and management of upland habitats in the English Pennines, Southern Uplands, central Highlands and Scottish islands, where the species presently occurs and is projected to remain at highest density in future, should therefore remain a conservation priority, highlighting the importance of this work.

Research by the BTO, just published in the journal Global Ecology and Biogeography, shows that the diversity of Britain’s birds has increased with a warming climate, but this was accompanied by a loss of habitat specialists. Using Breeding Bird Survey data from 1994 onwards, scientists at the BTO found that recent temperature increases had a positive effect on the number of bird species. However, there was also a negative effect of rising temperatures on ‘specialist’ species (species with specific habitat requirements). It appears that the winners from recent climate change were already common habitat generalists that have expanded their ranges, such as Great Spotted Woodpecker - up by 139%, likely at the expense of habitat specialists such as the Grey Partridge and Corn Bunting, which have declined by 50% and 29%, respectively, over the period of the study. Overall, this means that with climate change, bird communities across the UK are becoming more similar to each other as vulnerable range-restricted species are outcompeted by more resilient common species.

Newly published work by BTO scientists suggests that the increasing abundance of three widespread deer species, Reeves’ Muntjac, Roe Deer and Fallow Deer, have contributed to population declines of several breeding woodland birds in lowland England. The research applied novel analytical techniques to data collected through the Breeding Bird Survey, and indicated that populations of five bird species associated with dense understorey habitat have been depressed at sites where deer have increased. The two species of conservation concern, Common Nightingale and Willow Tit, are likely to have been worst affected. Modifications to the understory through deer browsing are thought to underpin these declines. Since high deer populations are now prevalent and likely to be affecting woodland biodiversity in large parts of lowland England, broad scale and co-ordinated deer management is required, and could usefully target areas that still support high populations of species sensitive to deer.