Summer migrants stay for longer as the UK climate warms

New BTO research has used volunteer data from long-running citizen science schemes to show how the timing of bird migration to and from the UK has changed since the 1960s.

Data collected by volunteer citizen scientists have been used to show how the timing of bird migration to and from the UK has changed since the 1960s. The spring arrival dates for 11 of 14 common migrants have got significantly earlier, with six species, including Swallow, House Martin and Chiffchaff, coming back to breed more than 10 days earlier than they used to. Species that advanced their timing of arrival also showed the most positive trends in abundance over this period.

BTO ecologists, led by Stuart Newson, compared data from the

Inland Observation Point

Inland Observation Point (PDF, 79.88 KB)

survey, which ran from 1962-1966, with information collected from 2002 to 2011 via

MigrationWatch

MigrationWatch (PDF, 72.58 KB)

and BirdTrack. The change in spring arrival across species equated to an advance of 0.22 days per year on average. In addition to the early arrival, four species were found to depart for their wintering grounds significantly later than previously. As a consequence of earlier arrival and for some species later departure, nine of 14 species spent significantly longer in the UK in the 2000s than in the 1960s.

These changes in bird migration are likely to be a response to warming on the birds’ UK breeding grounds. The extended stays in the UK may have benefited some species in allowing birds to lay more than one clutch, when they previously would not have had time to attempt to raise an extra brood because conditions were not suitable. Studies such as this are important in understanding how birds can adapt to climate change, and the effect of their response to their population dynamics at a time when many species are in decline and effective conservation measures are being sought.

The authors thank the volunteers who collected data for the three schemes in this study. BirdTrack is a partnership between the BTO, RSPB, BirdWatch Ireland, the Scottish Ornithologists' Club and the Welsh Ornithological Society.