Llanelli Naturalists Newsletter - Winter 1992/1993
Barry Stewart
During December 1992, F.B. Jenkins found three Chiffchaffs Phylloscopus collybita feeding on the new sewage filter-beds adjacent to the quay at Kidwelly. A subsequent visit by R.O. Hunt et al revealed a minimum of eleven individuals, two of these were paler and greyer than the other more typically coloured birds.
There are three races of Chiffchaff that occur in Britain this time of year: P. c. collybita is the nominate race which is most frequently encountered. It breeds in western Europe (including Britain) and is the darkest and greenest race with a yellowy wash on the supercilia, throat and breast: P. c. tristis is a rare visitor from Siberia and is pale and grey-looking, sometimes with a brownish or faint olive tint to the upperparts, but - more importantly - never shows any yellow tones around the face. It usually has jet black legs. P. c. tristis normally spends the winter months south of the Himalayas, but it is a regular drift (passage) migrant to Britain which sometimes also overwinters (Simms, 1985). Its regular call is said to be very plaintive and "sad" note, comparable to one of the melancholy notes of the Coal Tit - a "swea-oo" (Catley, 1981). The other race P. c. abietinus breeds in Scandinavia and has intermediate plumage between the two, with gradation occurring across its range.
On the 9th January 1993, armed with mist nets and camera, I made an attempt to catch a sample of the afore-mentioned waifs so I could examine and photograph the variation, and to try and make an accurate identification of the races occurring. It took only five minutes before I caught my first bird, it being one of the grey type. According to Svensson's Ringers Guide it showed characters closest to "tristis" but with a little "abietinus" thrown in. I trapped and ringed another of this type five minutes later and two typical "collybita". Only recoveries of birds at breeding sites would reveal their true racial identities, but it is likely that the grey birds originate from E. Scandinavia\W. Siberia, and the greener individuals are British or near continental.
The birds are still present at the time of writing (14 Jan) and can be seen easily from the gates at the sewage works along with many other species. The filter-beds will no doubt become a regular venue for local birders who are prepared to put up with the smell. Chiffchaffs also winter, rather irregularly, at other sites around Llanelli, "Ffordd-y-Wagen" and the Ashpits Pond area west of Pwll being one favoured area. It would be useful if readers are aware of the possibility of one of the northern races of Chiffchaff occurring and check any birds that they may come across; of course definite identification may not be possible.
The association of wintering Chiffchaffs with sewage works is well known with, for example, Penhallurick (1978) noting up to 37 birds at such a site in west Cornwall, where they (as at Kidwelly) fed on the ground amongst the bacteriological oxidation filters, utilising surrounding herbage and bushes in milder weather. Unlike that other regularly wintering warbler - the Blackcap - the Chiffchaff is entirely insectivorous. A photograph showing a wintering Chiffchaff on a sewage filter-bed (at St. Erth in Cornwall) is given in Simms (1985: p304).
References
Alexander, H.G. (1951). Northern chiffchaffs and kindred Phylloscopi. Brit. Birds 44:358-360
Catley, G.P. (1981). Unusual races of three warbler species recorded in 1981. Lincs. Bird Report 1981:37
Penhallurick, R.D. (1978). Chiffchaffs wintering at sewage-works in west Cornwall. Brit. Birds 71:183-186
Simms, Eric (1985). British Warblers. The New Naturalist Series. Collins. Chap. 29: 304-317
