Migration Records for Kansas Birds 101 



whether a given bird shall be considere;l very rare or rare 

 or not rare. Besides some of the "rare" birds are as plen- 

 tifnl here as elsewhere in their range, but a fair consider- 

 ation seems to place the number of those that can be con- 

 sidered bona fide Kansas birds at 220. If we include those 

 that are rare but omit those that are very rare the list is 

 increased to 300. Twenty-four of the not rare occur only 

 in western Kansas, though many of this list are merely 

 subspecies, scarcely distiuguislmble from the eastern form. 

 Twenty one occur only in tlie eastern part and four or 

 more occur only along the southern border. 



Analyzing the population still further we see that 42 

 of the 220 that are not rare are year-round residents; 98 

 are summer residents; 11 are Avinter residents only, and 

 82 are migrants. Here again, however, much depends upon 

 the judgment, for many, such as bluebirds and robins and 

 flickers migrate for the most part, but remain in small 

 numbers; others, such as many of the migrating ducks, 

 may occasionally spend the winter or summer Avith us. 



It is the purpose of this paper to deal with the times 

 of migrations and not the causes, but a word will not be 

 amiss on this latter subject. It is almost universally 

 agreed b}' those who have given the subject consideration 

 that tiie primary controlling factor of migration is the 

 food supply. Birds are better equipped than any other 

 animals to withstand cold. But when cold weather cuts 

 off the supply of insects and when snows threaten to cover 

 up the plentiful supply of seeds there is nothing else to do 

 but go where food may be liad. In the spring, warblers 

 and cuckoos may not come back until leaves appear, since 

 they gather their food from the leaves. Flycatchers and 

 swallows may not appear until insects are flying. Those 

 tliat come early and those that spend the winter with us 

 must have some source of food which they can depend 

 upon. Instinct, however, which is a safe guide, comes in 

 to supplant this primal impulse in guiding the bird's 

 actions. Usually it does not change the time of migration 

 a great deal, though we have many birds such as the pro- 



