Phylloscopus collybita – SIFF-SAFF/SIFF SIAFF – Breeding summer visitor, passage migrant and winter visitor
|No of tetrads occupied||380 (of 478)|
|Percentage of tetrads||79.5%|
“This tiny bird is by far the most numerous of our summer visitors” said Mathew (1894) of the Chiffchaff, and it remains a widespread breeding species in Pembrokeshire. Lloyd (in his diaries for 1921-1934) and Lockley et al. (1949) considered it outnumbered the Willow Warbler in the breeding season, with Lloyd estimating a ratio of at least 2:1 in favour of the Chiffchaff. Lockley (1957) later modified his view, stating the Chiffchaff was “probably” more abundant than Willow Warbler. Using data from census work on Dyfed Wildlife Trust reserves at Rosemoor, Old Mill Grounds and Pengelli Forest an estimate for average breeding density of about 15 pairs per tetrad was obtained, suggesting a total county population of around 6,000 pairs; the estimate for the Willow Warbler is seven times this amount.
Overwintering birds obscure the validity of early and late dates of migrants. However, they do not winter on the islands, so passage dates quoted here are based on islands data only. The first Chiffchaffs usually arrive in the middle of March, but sometimes from 3 March stragglers to the end of the month, peaking in the islands in the autumn between July and 9 November, with one at Skomer from 17 to 30 November 1987.
Birds resembling the grey northern race P. c. abietinus and paler eastern race P. c. tristis have been noted on both spring and autumn passage.
The Chiffchaffs which regularly winter in Pembrokeshire, mainly in woodland, including Slebech and Bosherston, and willow carr, such as Castle Pill, are not necessarily birds which have bred locally.
LOCKLEY, R.M. 1957. Pembrokeshire. London, Robert Hale.