142 HABITS OF BIRDS. 



the same is incomplete; yet, on the supposition 

 that it is not the same, but successive pairs, which 

 are observed in the same place, we are led to the 

 curious inquiry how the death or disappearance of 

 one pair is supplied by another. We have in more 

 than one instance observed a pair of magpies nestle 

 on the same tree for a series of years, where they 

 reared a brood of four or five young ones every 

 season. All of these disappeared from the neigh- 

 bourhood ; at least, we observed no increase in the 

 number of nests. In one instance we observed a 

 magpie's nest thus successively occupied for ten 

 years. 



The continuance of a nest in the same spot for 

 several years is more remarkable in the case of 

 migratory birds than in that of magpies, which do 

 not migrate, and seldom go to any considerable 

 distance from their breeding trees. There has been, 

 in a garden adjacent to ours, the nest of a black-cap 

 (Sylvia alricapilla) for a succession of years, and 

 broods have been successively reared there, with- 

 out any observable increase in the population of the 

 species. Yet this bird, which is little bigger than a 

 wren, weighing only half an ounce, has to traverse 

 annually the whole of the south of Europe, and 

 probably a great proportion of the north of Africa, 

 exposed, of course, to numerous accidents, as well 

 as to occasional scarcity of its appropriate food. 

 From the regular annual restoration, however, of 

 this nest at the same spot, it is obvious that one, if 

 not both of the black- caps, must have been wont to 

 perform this extensive migration to and from Af- 

 rica as safely as the more hardy cuckoo or the 

 more swift-winged swallow. During the spring of 

 1831, the back-caps, which we suppose to be the 

 same birds, from their keeping to the same place 

 of nestling, were more than usually late in arri- 

 ving ; for in another garden about a mile off there 

 were young in the hereditary nest of black-caps 



