NESTS AND NEST-BUILDING IN BIRDS 255 



a height of from lo to 40 feet they would be Hkely to 

 remain until ready for flight, as Audubon remarked. The tree 

 nests, as this excellent field naturalist also noticed, are con- 

 siderabl}^ greater in circumference than those built on the ground, 

 and this fact tends to greater security from accidents, while it 

 affords the chicks more ample room for exercise. On the whole 

 tree nests undoubtedly favor the gull chick, but they do not favor 

 the parent directly for it must bring more food to satisfy the 

 hunger of its young; evidently there can be no foraging for 

 insects, a privilege enjoyed by all birds reared upon the ground, 

 for many weeks, before they take to the water and are ready 

 for flight. 



Upon the strength of all the facts at hand we are bound to 

 conclude that individual variation in the position of the nest 

 for the gull, has no immediate reference to protection from man 

 or from its few common enemies ; it may favor the young under 

 certain conditions, but the variation is often of too slight a 

 character to have any significance. This was particularly well 

 illustrated in an allied species at one of the little Weepecket 

 Islands, in Buzzard's Bay, Massachusetts, where in July, 1902 

 I found a single nest of the roseate tern, raised two or three 

 feet above the level of the rocks and sand and fixed between 

 upright culms of sedge, a variation in building habit the more 

 striking since all the other nests were upon the ground. Here 

 again the variation could not be attributed to protection either 

 sought or gained, since it was the most conspicuous nest of the 

 little colony. 



Many cases could be given of novel, difficult or even fatal 

 nest sites being adopted by various birds, and in the first instance 

 repeatedly chosen, regardless of the teachings of experience. 

 A good illustration of the latter is seen in the stupid persistence 

 of the eaves swallow or house martin {Hinindo urbica), as 

 described by Gilbert White. ^^ " Birds in general " says the 

 naturalist of Selborne, "are wise in their choice of situation; 

 but in this neighborhood every summer is seen strong proof 

 to the contrary at a house without eaves in an exposed district, 

 where some martins build year by year in the corners of the 

 windows. But as the corners of these windows (which face to 

 the south-east and south-west) are too shallow, the nests are 



^' Natural History and Antiquities of Selborne. London, 1883, p. 137. 



