Blackcap photographed at St Peter Port [SPP] on 29/12/2017 Photo: © Mike Cunningham (visit site)

Blackcaps are a common summer migrant across all of western Europe northwards to southern Scandinavia. During the late 1800s, Blackcaps were a regular 'but no means numerous summer visitant' in Guernsey (Smith) and between 1921 and 1939 it was uncommon (Dobson, Transactions). It is currently more numerous during the breeding season and a common spring and autumn passage migrant. Since the early 1960s, small, but increasing, numbers have wintered in the islands.

In spring, Blackcaps start to pass through the island in the second week of April, peaking in the fourth week in April and passage continues through until the third week in May. The mean date of known migrants passing through Guernsey (i.e. those birds which were ringed or recovered elsewhere) is 27 April.

During the breeding season, Blackcaps can be found in most of the wooded valleys along the south coast, in suitable habitat along the west coast escarpment and in the parks and larger gardens. The Breeding Bird Survey showed it to be widespread across the southern end of the island but rare or absent from the low-lying north, presumably due to the lack of suitable wooded habitat. The increase in the number of breeding pairs is likely to reflect the increased availability of woodland on the islands from the middle of the twentieth century.

In autumn, passage birds pass through later than most other warblers with the peak passage in the last half of September and the first half of October.