AMERICAN WAUBLERS. 



61 



Origin of the Genera and Distribution. While a few species of 

 of the Wood Warblel's ( Detidroica ) are still to be found scattered through the 

 sub-tropical region of America as residents, audit is highly probable that they all 

 originated there or further south, the greater number now return to their ances- 

 tral homes as winter visitors, migrating further north in summer to breed. Ex- 

 ceptions to the rule that all the individuals of all the species migrate south in 

 winter, may be found in the Yellow-rump, in which species, although a large 

 number migrate as far south as Florida, and some even to the West Indies, many 

 remain further north: some spending the winter in Massachusetts. Another ex- 

 ception, but in another way, may be found in the Pine Warbler. In this species a 

 large number migrate northward in summer, but there are also a large number 

 of individuals that are constantly resident in the Carolinas and southAvard to 



Fig. 36. 



A, tongue of Yellow Warbler ; B, same of Chestnnt-sided, both enlarged. C, section of 

 stomach of Chest imt-slded ; D, entire stomach of same ; H, section of stomach of Yellow 

 Warbler; c, lining membi-aiie; W, walls; P, proventriculiis ; D, duodenum; I, pancreas: II, in- 

 testine. E, inner side of bronchial tube of Yellow Warbler, enlarged ; F, outer side of syrinx 

 of same; T, tympaniform membrane; v, bronchial tube; w, windpipe; II, inner bronchialis 

 muscle ; O, ouier of same ; Ti, sterno-tracheal muscle. 



Florida. While, beyond doubt, the Yellow-rumps are showing an inclinution to 

 abandon the habit of migration, this is not so certain in regard to the Pines ; it 

 may be possible that they have, comparatively speaking, recently began to acquire 

 the habit of migration. But without pausing at present to further consider these 

 interesting problems, we may state that, as a genus, the species of Wood Warb- 

 lets are inclined to be migrants, and in migrating to push northward a consider- 

 able distance, often, at least, to the borders of the north temperate zone. 



On the other hand, among the Golden Warblers, one species only, the Yel- 

 low, is found north of the sub-tropics. Some species have become residents in 

 certain of the W^est Indies, but many Avinter in northern South America, Avhich 

 Avas undoubtedly the original home of all members of this genus. 



