i62 Nesting Status of the Black-headed Gull in Yorks. 



birds first came in 1910, about 50 or 60 of them, and stayed 

 the siunmer. In Kjii they came in much larger numbers. In 

 igi2 there were still more gulls. ' Until now I had never 

 looked for eggs, but in the spring of 1912 I got a boat and found 

 large numbers of eggs on the islands.' The birds increased 

 in numbers in 1913 and 1914. In 1914 he estimated that they 

 would exceed 1000 pairs. ' In 1915 they were only here in 

 small quantities, and I was told the reason was, that the 

 large quantities in the previous years had eaten up all their 

 natural food in this district, and that they had gone to nest 

 elsewhere where the food was more plentiful.' 'They in- 

 creased in numbers each year in 1916, 1917, and in 1918, 

 when they again got to a great number, but not so many as in 

 1914.' ' In 1919 and 1920 the numbers again decreased, 

 probably owing to the shortage of nesting ground, as almost all 

 of the islands have been washed away with the floods, leaving 

 it almost one clear sheet of water. In 1920 there would 

 be probably about 150 pairs nesting here.' 



The inverted commas include extracts from Mr. Fox's 

 excellent description of this colony. 



Fly Flat Reservoir [Halifax Waterworks). — Cock Hill 

 Moor, near Denholme. This was the first nesting colony of 

 Black-headed Gulls I ever saw in the West Riding, I think 

 in the year 1900 or 1901 — when there would be about 25 to 30 

 pairs present. A note in The Halifax Natitralisl (Vol. IV., 

 page 58, Aug., 1899), written anonymously, implies this 

 colony must have been founded about 25 years ago. The 

 notes cannot refer to any other colony than that at Fly Flat ; 

 but to make certain I quote them in full. ' Though known to 

 but few people, there is an undoubted, though small, gullery 

 in an unfrequented part of the parish, where the gulls {Larus 

 rudibundns) have been breeding for the last few years in varying 

 numbers. Last year they were estimated to be forty pairs, 

 and about half-a-dozen nests have been seen this spring.' 



I have visited this colony two or three times since, but never 

 later than 1910, and the birds present have varied from 

 about twenty to fifty pairs. Mr. Walter Greaves, who has 

 visited the colony several times during later j^ears, confirms 

 this estimate, and adds ' there were usually very few nests.' 

 Yet a very good field observer estimated the number as about 

 100 pairs in 1918. No doubt the numbers fluctuate from year 

 to year. Mr. H. Waterworth informs me that there were 

 more than twenty nests in 1919 and 1920. 



A marked bird in this gullery, on June 5th, 1915, and re- 

 ported by Mr. W. Greaves, had been ringed as a nestling at 

 i)elamere Forest, Cheshire, on June 9th, 191 3 {British Birds, 

 Vol. IX., page 271). Another bird found dead in the breeding 

 season three years after it had been ringed at Llyn Mynyddlod, 



Naturalist 



