By Helen BriggsBBC News
5 December 2017
Migratory birds are arriving in the UK earlier each spring and leaving later each autumn, a report has confirmed.
Some visitors are now appearing more than 20 days earlier than they did in the 1960s, according to the state of the UK's birds 2017 report.
The swallow, for instance, is arriving 15 days earlier than 50 years ago.
Ongoing monitoring is essential to track the future effects of a changing climate on birds, says a coalition of wildlife organisations.
The report is by the Royal Society for the Protection of Birds (RSPB), the British Trust for Ornithology (BTO) , the Wildfowl and Wetlands Trust (WWT) and the UK's nature conservation bodies. It pulls together data from the latest bird surveys and monitoring studies.
The report warns that there will be winner and losers in a changing world, with opportunities for some bird species but higher extinction risks for others.
Some, such as the night heron, are breeding in the UK for the first time as their range expands north, while others, such as the snow bunting are in decline.
Dr Daniel Hayhow, lead author of the report, said familiar species such as swallows and sand martins are changing their migratory behaviour.
''We need to take that almost as a warning sign,'' he told BBC News.