42 Proceedings of the 



also because the geographical location of Nebraska is such as to 

 bring to its borders forms from both east and west. 



The families of Passeres show some striking contrasts. Tyran- 

 nidae, Icteridae, Hirundinidae. Vireonidae, Mniotiltidae, and 

 Turdidae are relatively numerous. This may be explained in the 

 case of the Hirundinidae by the fact that the forms do not show 

 a tendency to break up into subspecies and are of wide distribu- 

 tion; in the case of the Mniotiltidae by diis fact and also by the 

 fact that in the relatively few cases where subspecies occur, Ne- 

 braska receives its share of both eastern and western forms ; and 

 in the case of the other families by the occurrence of both eastern 

 and western subspecies. 



Nebraska is relatively deficient in Fringillidae, which seems 

 particularly surprising, and in Alaudidae, Corvidae, Troglody- 

 tidae, Mimidae, and Paridae. The family Troglodytidae reaches 

 its highest development in tropical America, and the species in- 

 crease rapidly in number as we go southward. The others show a 

 strong tendency to the formation of local races, more numerous 

 west and south, and in the case of the Corvidae, and especially 

 the Paridae, this is accompanied with a minimum tendency toward 

 migration. 



Ill 



If for the purposes of further analysis we limit our discussion 

 to those birds which make their home in Nebraska we shall deal 

 with only 232 species and subspecies, including all those listed 

 above as residents, those summer birds which can in no sense be 

 considered stragglers, and species which formerly bred but are 

 now extinct. It is interesting to observe in what direction from 

 Nebraska lie the centers of distribution of these forms during 

 their breeding season. In the compilation of these lists we have 

 depended upon the last edition of Coues' Key (1903) and the four 

 volumes, now published, of Ridgway's Birds of North and Middle 

 America. Of these birds the following are of general distribution 

 in North America : 



