34 THE RAPTORIAL BIRDS OF IOWA 



torial birds brought to his laboratory for a period of years were 

 submitted for examination. I wish also to thank Professor J. H. 

 Paarman and Miss S. G. F. Sheldon, of the Davenport Academy of 

 Sciences; Professor H. W. Norris, of Grinnell; Mr. E. R. Harlan, 

 of the State Historical Museum, Des Moines; Mr. F. C. Pellett, of 

 Atlantic; Mr. Charles Buettner, of Burlington; Mr. G. H. Berry 

 and Mr. John Cobden, of Cedar Rapids ; Mr. George Binge, of Mt. 

 Vernon, and Mr. A. F. Porter and Mr. Christ Hoeg, of Decorah. 



BERT HEALD BAILEY. 

 STATE UNIVERSITY OF IOWA, 1917. 



TOPOGRAPHY AND DISTRIBUTION. 



Few states present a more uniforrh surface with less topographic 

 relief than Iowa. Planed by successive ice sheets everywhere ex- 

 cept in a limited area in' the extreme northeast, and drained by the 

 tributaries of two great rivers, there is to be found nothing more 

 bold than a divide whose gentle slopes to the east and west separate 

 the drainage waters of the state, from the Okoboji lakes to near 

 the middle of its Missourian boundary. These eastward trending 

 streams in places have cut through limestone many feet in thick- 

 ness, making picturesque palisades beautified by the abundant cedars 

 which grow in their crannies or crown their heights. Cottonwood, 

 elm, basswood, oak, and many other trees stand in the flood plains 

 or forest the higher ground almost continuously along their courses. 

 West of the divide there are fewer trees skirting the streams, 

 which flow through the rich alluvial soil. The western and espe- 

 cially the northwestern part of the state, while comparatively tree- 

 less, has at present groves that break the monotony of the prairies 

 and that have changed not a little of the fauna inhabiting this sec- 

 tion of Iowa. The rugged driftless area north and east of Turkey 

 river is illy adapted to prairie-loving forms, while sections in the 

 north and west afford no attraction to those that require the forest. 

 The wooded Missouri bluffs and bottoms on the west make condi- 

 tions similar to those found to the east along the Mississippi, and 

 though not so abundant, all the birds of prey common to the Missis- 

 sippi valley are to be found along the Missouri. The rivers are 

 highways for bird migration, and since so large a part of the rap- 

 torial fauna is comprised of species that prefer the woods these are 

 the parts of Iowa where the birds of prey are most abundant. The 

 accompanying chart divides the Hawks and Owls into three groups 



