Winter Gull Roosts in Suffolk Adam
Bimpson
Introduction The importance of Suffolk as a County for gulls has been well documented, both historically by Ticehurst (1932) and Payn (1978) and more recently through the County bird reports. Most of these data have concentrated either on breeding totals e.g. the importance of Orfordness with its Lesser Black-backed and Herring Gull colony, or specific records of unusual occurrences and scarce species. Little work had been attempted to obtain a year round picture of the numbers or distribution of Suffolk's gull population. 1993 saw an attempt to redress the balance with a continuation of the British Trust for Ornithology's (BTO) Winter Gull Roost Census. The information obtained is slowly building into a valuable source of information relating to the wintering gull population in the British Isles. The BTO Winter Atlas (Lack 1986) provides a good example of the use made of such information, although it can be difficult to ascertain patterns and trends that occur at County level when using data gathered on such a large scale. The Winter Gull Roost Census has been carried out in Suffolk once every decade since its commencement in 1953. It is usually during the first winter period (January-March) that the roosts have been counted, concentrating on January, thus providing a mid-winter population estimate. Previous surveys have produced a rather incomplete coverage of the County by mainly concentrating on the well known sites, thus leading to a fragmented knowledge of the wintering gull population. The coverage obtained in the 1993 survey has been the most complete to date with both coastal and inland waters being studied. This paper aims to provide an insight into the wintering populations of gulls within the County and to gauge their relative importance on the national scale. Methods Observers were asked to visit their allocated site just prior to sunset on any convenient date between January 21 st and 31 st 1993, but preferably during the weekend of 23rd/24th. Totals of gull numbers were collected as either actual or estimated figures, incorporating birds already present on the surface or in flight lines coming in to roost. Full instructions were given on the back of the official census cards. Other details were also collected includ-