PREFACE. XIX 



liable authorities, because in particular instances they do not 

 accord with their own observations. Neither should differ- 

 ences in habits, in song, etc., be taken as infallible evidence 

 of a difference of species. . . , Howuniversally the Chipping 

 Sparrow (^Spizella socialis) breeds in trees, and generally at 

 an elevation of several feet, is well known, but several au- 

 thentic instances of this bird's nesting on the ground have 

 come to my knowledge, one of which I myself discovered. 

 Variations of this character in other species are of occasional 

 occurrence, examples of which have doubtless been met with 

 by every experienced collector. 



" The materials which birds select in the construction of 

 their nests are well known to vary in different localities ; the 

 greater care exhibited by some species to secure a soft warm 

 lining at the north that are much less precautious in this re- 

 spect at the south, is already a recorded fact. Aside from 

 this, the abundance of certain available materials occurring at 

 only particular localities gives a marked character to the nests 

 there built, which serves to distinguish them from those from 

 other points. Some of the Thrushes, for instance, make use of 

 a peculiar kind of moss at some localities that elsewhere, from 

 its absence, are compelled to substitute for it fine grass or dry 

 leaves. At Ipswich, on Cape Cod, and perhaps generally in 

 the immediate vicinity of the sea, the Purple Graokles ( Quis- 

 calus versicolor) and Eed-winged Blackbirds QAgelceus phce- 

 niceus), and in fact numerous other species, in building their 

 nests often use little else than dry eel-grass or ' sea-wrack,' 

 which results in nest-structures widely different in appear- 

 ance from those of their relatives residing in the interior. 

 Every egg-collector is aware of the wide variations eggs of the 

 same set may present, not only in the markings and in the 

 tint of the ground color, but in size and form, and especially 

 how wide these differences sometimes are in eggs of different 

 birds of the same species. Also how different the behavior of 

 the bird is when its nest is approached, in some cases the par- 

 ents appearing almost utterly regardless of their own safety 

 in their anxiety for their eggs or helpless young, while other 

 parents of the same species quietly witness the robbing of 



