Temporal changes in the migration phenology of turtle doves Streptopelia turtur in Britain, based on sightings from coastal bird observatories

Using daily counts of birds seen at six coastal bird observatories in southern and eastern England, we explored the migration phenology of turtle doves during the period 1963 to 2000. Annual totals increased threefold up to the late 1970s then decreased again, in accordance with the BTO Common Birds Census (CBC) index of abundance. Median annual spring arrival and autumn departure dates of turtle doves were not related to abundance (CBC index) or mean temperature in spring or summer respectively. Although median annual spring arrival date has not altered over the 38-year period, median annual autumn departure date has become earlier by 8 days. This has resulted in a shortening of the breeding season by 12 days, which ties in with a reduction in average number of nesting attempts per pair observed by a recent autecological study. It is possible that breeding turtle doves are now out of phase with peaks in food availability. This may have resulted in reduced breeding performance and earlier termination of the breeding season, and may have partly contributed to the decline of the species.