180 



OoNDiTfONS Effecting the Distribution of Birds in Indiana.* 



By Amos W. Bvti.ek. 



GENERAL CONDITIONS. 



The re^iihir aiuui:il movements of birds, their migrations, are- 

 among- the most striking of the manifestations of Nature. "With the 

 revivifying breath offspring, the absent bfrds return. Last fall, when 

 the summer's work Avas done, they went to warmer climes. Now. they 

 seek anew their breeding grounds. Some make their homes with us; 

 others go farther nortli to rear their j-oung. The semi-annual ebb 

 and flow of these tides of bird-life, the Itreeding range and the food 

 supply are general factors that enter into the distribtition of liirds 

 everywhere. Our ancestors noted them as signs of the seasons. They 

 exist today, though we do not see them so readily because of our 

 changed conditions. 



ZOOLOGICAL AREAS. 



Indiana is a meeting-ground of various birds. Into it range typical 

 forms of different zoological regions. From the west, are prairie birds; 

 slightly tinging the north, are northern forms: wliile the dominating 

 influence of the lower part of the State is .sotithern. Indiana lies within 

 the eastern (Atlantic) faunal province. According to Mr. Ajlen, it Ms 

 distinctively Carolinian (Bull. Mus. Comp. Zor>l. II. No. 8. pp. 893-395), 

 yet the southwestern part is within the range of many birds char- 

 acteristic of the Louisiauian Faima (Atistroriparian Province of Prof. 

 Cope, Btill. U. S. Nat. Mus. No. 1. 18To. pp. (jT-T1i. I»r. Merriam would 

 include the bulk of the State in the Upper Austral Zone, the Lower 

 Austral Zone reaching into southwestern Indiana and the Transition 

 Zone influencing the northern part (Bull." Xb. Id Biol. Surv. V. S. Dept.. 

 Agr. 1898). 



•'Contributions from the Zoological Laboratory of Indiana University, No. 37.. 



