BTO, Migratory Birds and Climate Change

Waders shift their winter distributions

The world climate is changing as a result of human activities. In Britain, during the 20th Century, annual average temperatures rose by almost 1 ºC. By 2080, temperature is expected to rise by 2 to 3.5ºC and sea-level by between –2 and 86 cm. The distributions of wildlife and plants are changing throughout the world and some fingerprints of climate change are visible in Britain. Waterbird surveys provide one of the most largest datasets in the world: more than 3,000 sites have been monitored across Europe for over 25 years. Such information could guide future government conservation strategies. This may be necessary given the importance of Europe for waterbirds.

UK CIP scenarios of future temperature change (Hulme et al. 2002).

Changing wader distributions

Since the mid-1980s seven of nine species of wader occurring in internationally important numbers have moved in an eastwards direction along the winter isotherms with increasing mean winter temperature (Austin & Rehfisch 2005).

click on the image to see a larger version

Curlews, like many other waders have declined in the southwest, but increased in the northeast

Between 1980 and 2001, the weighted centres of the over-wintering populations of seven species of wader in north-west Europe have undergone marked shifts in a northerly or north-easterly direction. Species such as Curlew, Grey Plover, Dunlin and Black-tailed Godwit have shifted their distributions by more than 50 miles (Maclean et al. in review).


Specific responses to climate change
On UK estuaries, the smallest species of waders have undergone the greatest shifts in their distribution, as would be expected if such shifts are due to changes in temperature (Austin & Rehfisch 2005).

Relationship between temperature response and body mass
In north-west Europe, changes in site abundance of all seven species of wader included in analysis is temperature-dependent. Numbers are increasing in response to warming temperatures on colder sites, but not on warmer sites (Maclean et al. in review).

Future changes
Based on present associations between waders and weather, some wader species, may decline considerably under the 2080 UKCIP scenarios and if flyway populations do not decline Britain may no longer hold internationally important populations of these species (Rehfisch et al. 2004).

click on the image to see a larger version Ringed Plover distributions (a) in 1984-85 and predicted densities in 2080 under the (b) medium-low and (c) high UKCIP climate change scenarios relative to the 1960-1990 baseline
Observed historic increases in wader numbers over-wintering in north-east Europe are likely to continue. The Baltic region is likely to host increasingly important numbers of waders. Declines may occur in some parts of south-west Europe (Maclean et al. in review).

click on the image to see a larger version Thirty-year trends in numbers of selected wader species in parts of the north-east and south-west of Europe. In the north-east numbers are generally increasing, but in the south-west decreases in France due to climate change are more than compensated for by increases due to a reduction in hunting pressure. In Wales, numbers are declining

Conservation implications

The recent decline in eight of the 14 species of common coastal wader in Britain could be due in part to the waders now wintering even further north and east, on the European mainland (Rehfisch & Crick 2003).

Waders are designated features of Special Protection Areas (SPAs) that regularly hold 1% or more of their flyway wintering population. As wader distributions change with climate change, numbers of some species on some British SPAs are dropping below the 1% threshold such as is the case for Dunlin on the Severn SPA.

Dunlin numbers on Severn SPA against international threshold (dotted line)

References
Austin, G. & Rehfisch, M.M. (2005) Shifting non-breeding distributions of migratory fauna in relation to climatic change. Global Change Biology, 11: 31-38. Hulme, M. et al. 2002. Climate change scenarios for the United Kingdom: the UKCIP02 scientific report. Tydall Centre, University of East Anglia, UK. Maclean, I.M.D. et al. (in review) Global warming causes rapid changes in the distribution and abundance of birds in winter. Global Change Biology Maclean, I.M.D. et al. (2005) WeBS Alerts 2003/2004: BTO Research Report No. 416, Thetford. Parmesan, C. & Yohe, G. 2003. A globally coherent fingerprint of climate change impacts across natural systems. Nature, 421, 37-42. Rehfisch, M.M. et al. (2004) The possible impact of climate change on the future distributions and numbers of waders on Britain’s non-estuarine coast. Ibis, 146, S70-S81. Rehfisch, M.M. & Crick, H.Q.P. 2003. Predicting the impact of climatic change on Arctic-breeding waders. Wader Study Group Bull., 100, 86-95.
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