70 HOMING AND RELATED ACTIVITIES OF BIRDS. 



familiar objects influence orientation more than those added after the laying 

 of the egg. The birds pay more attention to the nests of others than to any 

 other class of objects. 



In the case of some other nests, particularly those in crowded areas, I could 

 find nothing in the immediate neighborhood of the nest which seemed to influ- 

 ence the birds' orientation. At one time a nest was shifted 1 foot from its 

 original position and practically every object within a radius of 3 feet was 

 moved for the same distance in the same direction. The sand in this area 

 was smoothed out to change its appearance. Thus the original environment 

 was duplicated with 1 foot lateral displacement. The bird came back to the 

 position of the orignal nest, now completely obliterated, and gave nearly the 

 same set of reactions as that of the bird described in experiment 1. In this 

 case the recognition of the nest locality was upon the basis of some other 

 stimulus than that provided by the immediate environment. The same was 

 in part true of the nests described in experiments 4 and 5. 



THE ALIGHTING PLACE. 



The clue to the method of orientation in such cases is given by the behavior 

 of the bird described in experiment 5 in passing from her alighting place to 

 the nest. It seemed that this bird took its direction from some objects at the 

 alighting place and depended upon this place for re-orientation when con- 

 fused by changes in the position of the nest. The following observations 

 bring out the importance of the alighting place and the path from this to the 

 nest. 



EXPERIMENT 8. 



At the edge of the beach two piles of brush were thrown together in such a way as to leave 

 a small over-arched passage extending half way through between the piles and opening on 

 the beach to the westward (z, figure 5). A pair of sooties had their nest at the inner end 

 of this passage. The bird studied alighted always at the southern end of the brush pile, 

 walked around the southwestern corner, where there was another nest (x), and then followed 

 the western side of the pile to the opening of the nest. The path was complicated by a dead 

 bay-cedar branch (y), which projected from the face of the pile and forced the bird to stoop 

 and turn out to the left. The bird was seen to follow this path accurately in five successive 

 trips to the nest. I broke off the branch and removed it, leaving a clear path from x to z. 

 On the next two trips to the nest, the bird went through exactly the same movements of stooping 

 and turning out which had been required by the presence of the dead branch. 



FIG. 5. Nest environment described in experiment 8. 

 z, nest of bird studied; x and o, other nests; 

 y, branch of bay-cedar bush. 



I moved the egg out from under the brush to a point a foot west of its original position. 

 The bird returned immediately and went to the former position of the nest. She was 

 disturbed by the absence of the egg, came out slowly, and returned to the southwest corner 

 of the brush pile. She looked at the nest there, then turned and ran quickly along her usual 

 path to her own nest. This was repeated four times. The bird's movements in going from 

 the nest site to the corner of the brush pile had every appearance of hesitation and uncer- 

 tainty, a marked contrast to her behavior after she reached the point from which the 



