Motacilla alba yarelli – SIGLEN FRAITH – Breeding resident and passage migrant
|No of tetrads occupied||287 (of 478)|
|Percentage of tetrads||60%|
A common resident in Mathew’s (1894) day and a numerous breeder to Lockley et al. (1949). Today the Pied Wagtail subspecies yarrelli breeds throughout the county, but its distribution is a little patchy (see map). It is most numerous in the south of the county and in the Preseli Mountains area, being scarcer over much of the dairyland that dominates central Pembrokeshire. At an estimated average density of five to six pairs per tetrad the total population is about 1,400-1,700 pairs.
There appears to be a small spring passage, with birds in fresh plumage appearing briefly on the coast and islands.
Small numbers, up to ten at a time, are seen on autumn passage on the islands and passing down the coast, and a nestling ringed at St David’s in June 1963 was recovered in France in November 1963.
They form communal roosts during the winter. The roost sites are prone to change, sometimes after being used for years. Roost sizes are mainly between 100 and 300 birds but Lockley et al. recorded up to about 1,000 at Martletwy between January and March 1935.
White Wagtails subspecies alba pass through Pembrokeshire in both spring (from March to May) and autumn (late August to October), sometimes in considerable numbers, such as 200 at Skokholm on 15 September 1988. Many of these originate in Iceland, judging by ringing recoveries, but it is likely that others are Scandinavian, as their passage coincides with the occurrence of other species from that area, such as Grey-headed Wagtails, Scandinavian Rock Pipits and Bluethroats. Ringing also shows that birds passing through Pembrokeshire journey on to France and Spain on the return migration.