Breeding summer visitor and passage migrant. Not recorded in January and December
A common summer visitor to both Mathew (1894) and Lockley et al. (1949), today House Martins are widespread breeding birds (see map). Most nest on buildings, but there are also thriving cliff colonies at many places around the coast, as at Ceibwr and Nolton Haven, and a colony of three pairs was at Skomer in 1969. At an estimated 20 pairs per tetrad the breeding population is probably about 4,000 pairs.
The first House Martins usually arrive here in early to mid-April. However, birds occur from 20 March in some years, and really early birds were at Pointz Castle on 17 February 1958 and at Moylgrove on 23 February 1984, and one was found freshly dead at Dale on 10 February 1982. This latter record followed a period of southerly winds bearing Saharan sand, which might have borne the bird, displacing it in the same way as moths are taken way beyond their normal range. Northward passage continues on a broad front across the county but most densely at the coast, throughout April and May and into early June. They often pause over freshwater sites, particularly during rain or fog, when congregations of up to 200 occur, as at Pembroke Mill Pond on 17 April 1983.
Southwards movement occurs from late July and continues until October, with stragglers until 19 November in some years. The volume is probably larger than in spring with fewer concentrations, though 250 have been recorded at Skokholm.
Although principally a diurnal migrant they were recorded at lighthouse attractions at the South Bishop on 29 May 1975 and at the Smalls on 20 May 1984 and 29 and 30 September 1983.
Fieldwork 1984-88 (based on 478 tetrads)
Red = breeding confirmed = 197
Orange = breeding probable = 7
Total tetrads in which registered = 204 (42.7%)