The winter status of the Lesser Black-backed Gull, 1959–60

Weather conditions during the winter of 1959-60 were generally rather mild, and on the whole similar to those of 1949-50.After a mild and changeable November, December was wet and stormy, the mean temperature exceeding the 1921-50 average by 2.5°F in England and Wales, o.9°F in Scotland and o.4°F in Northern Ireland.January was also wet with mild periods, but there was a cold, snowy period in the middle of the month, and mean temperature exceeded the average by only 0.1°F in England and Wales and was o.5°F below average in Scotland and Northern Ireland.The first few days of February were mild and stormy, but a cold period lasted from the 6th to the middle of the month, and the mean temperature for the month was below average in each country.(This brief summary is derived from the Monthly Weather Reports of the Meteorological Office.) SUMMARY OF WINTER DISTRIBUTION 1 959-6oThe investigation showed that there had been a very marked increase since the original enquiry in the number of Lesser Black-backed Gulls wintering in the British Isles.A comparison of Figs.i and 2 will give a quick impression of the extent of this change.(It should be noted that February records are excluded from both maps to avoid confusion with early immigrants.)In 1949-50 only two of the Watsonian vice-counties came into the highest category of 5o and over, and Nottingham only by virtue of a single count on I December: in 1959-60, zo vice-counties fell into this group.A conservative total of separate counts for January, 1960, excluding any probable overlapping, was 2,80o, compared with 310 for January, 195o; a ninefold increase.About I,000 of this total were recorded within 45 miles of the Pennine gullery, a large total, but a considerably smaller proportion than in 1950.All the chief centres of mid-winter population had greatly increased their numbers.In the Bristol area the total of winter residents had risen from c. 20 to C. 150, near Cardiff from c. zo to over too, round Morecambe Bay from c. 150 to over 400.Comparisons in East Lancashire and the West Riding of Yorkshire are more difficult owing to fluctuations and local movements during both winters, but figures from the former district would suggest a rise from c. too to c. 400 and in the Yorkshire industrial area from c. 3o to c. 350.Developments in the London area have been even more striking.In 1949-50 there appeared to be a population of c. 30 feeding along the Thames in London; only a few were reported from the suburbs and Home Counties.The winter of 1959-60 produced only a moderate increase in central London, but large numbers appeared in Surrey, e.g.226 on Beddington sewage farm on 16 January, and on the North London reservoirs, e.g.170 at Hilfield Park on 20 December, and at least 200 on the Girling reservoir until the second week of January.But perhaps the most remarkable change has been in the West Midlands.Although this area was adequately covered in 1949-50 no Lesser