1907.] Food Habits of the Black-Headed Gull. 411 



Of the 100 birds examined 40 contained food which would 

 lead the bird to be classed as " harmful," e.g., fishes, cereals, 

 useful insects ; 47 contained " beneficial " food, e.g., injurious 

 insects and mollusca, carrion and waste animal matter, and 

 82 contained " neutral " food, e.g., earth-worms, Crustacea and 

 spiders, harmless insects and mollusca, and vegetable matter 

 other than cereals. As anticipated, it was found that the food 

 taken was very variable in description, varying not only 

 according to season and opportunity, but also apparently 

 according to individual taste. 



A very large proportion of the birds examined (42 per cent.) 

 contained earthworms, and if a staple food may be understood 

 as the one most generally and extensively taken, then earth- 

 worms may be regarded as the staple food of the species in the 

 district under consideration. Wireworms (see the Board's 

 Leaflet No. 10) were extensively taken, and 41 per cent, of the 

 birds examined contained these and the larvae of Tipulidcs 

 (crane-flies or daddy longlegs, Leaflet No. 11), both of which 

 groups of insects are decidedly harmful. Only one bird was 

 found to have taken harmful mollusca, but it was responsible 

 for 30 common slugs, Limax agrestis. Beetles — injurious, 

 harmless, and beneficial — were taken indiscriminately, and 15 

 per cent, of the birds examined had taken some species of 

 ground beetle (Carabidce). Flies were also largely taken. 



Fish as a food appeared to be sparingly eaten, partly from 

 want of opportunity, for the black-headed gull does not readily 

 obtain fish from water more than a few inches in depth, and 

 partly from the greater ease with which other food can be 

 procured at most seasons of the year. Only 9 per cent, of the 

 birds had fed upon fish of any description. Of 36 birds taken 

 on the Eden between Carlisle and Rockliffe only 7 contained 

 traces of fish. The writers of the report (Mr. D. Losh Thorpe, 

 and Mr. L. E. Hope, Curator, Carlisle Museum) say that 

 although they have had the black-headed gull under almost 

 daily observation on the [river Eden for several years, and 

 especially so during the 13 months the investigations have 

 been going on, they have never detected the bird injthe act of 

 catching a fish. 



The largest proportion of food was found to consist of vege- 

 table and animal matter considered neutral in nature, but 14 



