ANDERSON — THP: BIRDS OF IOWA. I37 



orons l)ir(ls are dependent upon the plants and insectivorous birds 

 upon the insects which appear with the rejuvenescence of plant 

 life. Through its effect upon the flora, therefore, climate has an 

 indirect but intimate effect upon the movements of most birds, with 

 the exception of a few resident species whose diet and .source of 

 food supply are only slightly affected by the .season. 



RANGE IN IOW.\. 



The range of the different species in the state has been taken 

 largely from the reports received from numerous observers, from 

 specimens in various collections, and from all available published 

 records. The following rule has been adopted for the admi.ssion 

 of a species to a state list: A specimen of the species must have 

 been captured within the limits of the state and preserved, or 

 crilicalh' examined by some person familiar with the species, or 

 capable of making a positive identification. A local or county 

 record, if casual or accidental for the region, must l)e substanti- 

 ated by a specimen captured and criticall}" examined, or if con- 

 spicuously marked, observed under fa\-oral)le conditions l)y one 

 familiar with that species. 



I have been compelled to omit some species from lists which 

 have been furnished me, as well as to relegate to a State Hypo- 

 thetical lyist some species which have been reported on insuffi- 

 cient evidence as occurring in the state. The wide-ranging habits 

 of birds, and the facilities for extended locomotion possessed by 

 them, make the occurrence of extra-limital species possible at 

 almost any time or place, and render the criticism of any observ- 

 er's records extremely unsafe. Experience has shown, however, 

 that additions are easily made to a faunal list, while errors seem 

 to have a facility in indefinitely perpetuating themselves. 



TOPOGRAPHY OF IOWA. 



The state of Iowa is situated between 40° 20' and 43° 30' north 

 latitude and 90° 15' and 96° 43' west longitude. Its extreme length 

 is from east to west, about 328 miles, its greatest width from 

 north to .south, about 215 miles. Its area is approximately 55,475 

 square miles. The following extracts are taken from a chapter 



