Census of Black-headed Gull colonies in England and Wales, 1958

A CENSUS OF ALL COLONIES of Black-headed Gulls (Larus ridibundus)in England and Wales was attempted in the breeding season of 1958.Through the medium of the Regional Representatives, members of the B.T.O. and local societies were asked to record all colonies.They were requested to complete a card, giving brief details as to the number of birds present, an accurate or estimated total of nests and the date of the count.A description of the habitat, together with the locality and National Grid Reference were also requested.In order to draw a comparison, where possible, with the 1938 census (Hollom, 1940) a separate questionnaire was also used asking reasons for increase and establishment, or decrease and extinction of colonies since that date.A request for the information to be returned to the organiser by the end of July, 1958, met with little success; in some cases reports were not received until early 1960.This has consequently delayed the presentation of this report. LOCATION OF COLONIESThe census of colonies in 1958 was fairly complete, with the exception of the north-west of England and the counties of Denbighshire, Caernarvonshire, and possibly Flint and Anglesey in Wales.This was partly due to the lack of effective co-operation in some areas.These areas are also difficult to count as they include large areas of remote moorland where the existence of colonies is often unsuspected.A total of 155 colonies was recorded for England and 30 colonies for Wales.Table I shows the number of colonies in each county where the species bred in 1958 compared with 1938.A full list of occupied colonies in 1958 is given in Appendix A. It can be seen that of the 1938 colonies, only 54 (4 1 per cent) are still in existence and 104 new sites are now being used.The main increase in colonies has been in the inland counties and appears to have been brought about by the availability of new habitats since 1938, which the species has been quick to colonise.The large number of sites, 155 in England and Wales occupied between 1938 and 1957, but deserted in 1958 (see Appendix B), gives some idea of the adaptability of this species in changing its nesting sites from year to year.Much of the movement is brought 56 BLACK-HEADED.GULL