BRITAIN'S BIRDS AND THEIR NESTS. 41 



Various shades of huffish brown and brownish oHve are 

 t3rpical, while the spots, which often run together into 

 large blotches, are much darker. All sorts of abnormali- 

 ties — too many to enumerate here — are not infrequently 

 found. The eggs in a single clutch, whether of normal 

 or abnormal type, generally resemble each other in con- 

 siderable degree ; but ' odd sets ' are not uncommon. In 

 defence of its eggs or young this Gull will swoop at 

 the head of the human intmder, often striking him with 

 its wings. 



Incubation lasts rather less than three weeks. The 

 young birds are covered with huffish down, with darker 

 spots above and paler down below. If undisturbed they 

 do not leave the nest for some days. Altogether they do 

 not make very hardy chicks, it seems, for the mortality- 

 rate among them is high. Although they swim with ease, 

 and apparently with pleasure, at an early age, they are 

 extremely liable to attacks of cramp afterwards, which only 

 too often prove fatal. Much harm may therefore be done 

 indirectly by the most innocent invasion of a gullery, 

 through frightening the chicks into the water at too early 

 an age. The immature plumage is assumed after a few 

 weeks, and the young Gulls scatter over the country. In 

 this plumage they have the head something like the 

 adults in winter, the mantle at first mostly dark brown, 

 but afterwards a mixture of light brown and gray, while 

 the bill and legs are dull yellow and yellowish red re- 

 spectively. The tail has a conspicuous dark terminal bar. 



The question of the food of the Black -headed Gull is 

 an important one, owing to the keen dispute as to 

 whether the species is to be considered harmful or 

 beneficial to man. This dispute has brought out the 

 necessity for the study of economic ornithology in this 

 country, and has shown the futility of acting on the 



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