The Scottish crossbill may be going; the black kite may be coming. Climate change appears to be widely affecting Britain's wild birds, a study shows.

Some bird populations are shrinking, some are increasing, and others are moving under the influence of rising temperatures, says the report from a coalition of conservation groups, led by the Royal Society for the Protection of Birds (RSPB).

The report has compelling evidence to indicate that although global warming is widely thought of as a phenomenon of the future, it is already changing the natural world. Hotter, dryer summers and warmer, wetter winters are starting to affect bird numbers, and mean we may soon lose some attractive species, such as the native crossbill of Scotland's pine forests, according to The State of the UK's Birds 2004, which is being launched today at the British Birdwatching Fair at Rutland Water.

But we may gain unfamiliar, charismatic newcomers moving into Britain as breeding birds from continental Europe, such as the black kite and the cattle egret. The report, produced by the RSPB with the British Trust for Ornithology, the Wildfowl and Wetlands Trust, English Nature, Scottish Natural Heritage, the Countryside Council for Wales and the Environment and Heritage Service of Northern Ireland, pulls together a mass of recent data on changes in British bird populations which appear to be climate-related. Although there are winners in this process, the losers attract the most concern.

Global warming seems to be hitting some bird species in three ways: by directly affecting the availability of their food, by affecting the state of their habitat, and by affecting their ability to migrate. The prime example of a food loss is with seabirds: 2004 was the worst breeding season on record for many UK seabirds, especially the guillemots and puffins of the northern isles, which suffered catastrophic breeding failure.