Migrant birds in hot water

A changing world

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 fingerprints of climate change are visible throughout the world.

Waterbird surveys

Waterbird surveys provide one of the most largest datasets in the world: more than 5,000 sites have been monitored across Europe and Africa for over 25 years. Such information could guide future national and international conservation strategies.

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Impacts of climate change on waterbirds

Climate change is a major threat to migratory waterbirds, according to a series of reports by the British Trust for Ornithology and Wetlands International (Maclean & Rehfisch 2008; Maclean et al. 2008b & c). Of 235 species of migratory waterbird occurring in Europe and Africa, all except one are experiencing some threat from climate change, and nine species face severe threats that could cause extinction.

The report, launched in September 2008 in Madagascar at the 4th Meeting of the Parties of the African-Eurasian Waterbird Agreement, highlights the need for international co-operation when it comes to helping migratory species cope with climate change and other environmental problems. When animals migrate, they often traverse political boundaries that have no inherent meaning to them, but which dramatically influence them due to the great differences that exist between countries in conservation policy. International co-operation is often required to reduce the many pressures they face.

With warmer temperatures, many birds are finding their current living conditions increasingly unsuitable. Some are shifting their ranges towards cooler climates. However, species such as the Crowned Cormorant, confined to the extreme southern coast of Africa, need land to nest on and are prevented from moving poleward by the presence of the sea. A similar situation exists for those species that breed in the high Arctic, such as the Sanderling.

Changing wader distributions

Curlews, like many other waders have declined in the southwest, but increased in the northeast. Source: Maclean & Austin (2008)

Specific responses to climate change

Relationship between temperature response and body mass

Future changes

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. 2008a).

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.

References

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. & Rehfisch, M.M. (2008) Guidelines on the measures needed to help birds adapt to climate change. AEWA Technical Series No. 26, African-Eurasian Waterbird Agreement Secretariat, Bonn, Germany.

Maclean, I.M.D. et al. (2008a) Global warming causes rapid changes in the distribution and abundance of birds in winter. Global Change Biology, 2489-2500.

Maclean, I.M.D. et al. (2008b) The Effects of Climate Change on Migratory Waterbirds within the African-Eurasian Flyway. BTO Research Report No. 486, BTO, Thetford.

Maclean, I.M.D. et al. (2008c) Migratory waterbirds and climate change: summary for policy makers. African-Eurasian Waterbird Agreement Secretariat Popular Series, Bonn, Germany. Available: here.

Maclean, I.M.D. & Austin, G.E. (2008) Wetland Bird Survey Alerts 2004/2005 (Release 2). BTO Research Report No. 492, Thetford. Available: here.

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.