Zoological Explorations. 281 



*■'■ instinct'''' even if explained as a no more comprehensible 

 '■'■ hcreditarv habit?'' 



Of course lack, of food is recognized as the prime factor in 

 causing migration, but we have still to answer the question : 

 Ho-.v do the birds knozi' zvhen and in zvhat direction to start on 

 tlieir mig ratiotis ? 



According to the generally accepted theory, the journev is 

 taken in response to an impulse which comes from zvithi)i, an 

 unconscious seeking for an unknown good. 



According to the view held by the writer this impulse 

 comes in the shape of a stimulus from vjithont and the act is 

 a conscious seeking for a more suitable clime, on the part of 

 the adults at least, the young simply following or imitating 

 their elders. 



There is much to indicate that this stimulus comes in the 

 form of the zvind. 



Any lield ornithologist knows that in temperate North 

 America, a warm rainy night in spring will bring a host of 

 new bird arrivals. The wind of course is southerly on such 

 a night. 



It is an equally patent fact that a cold windy night in the 

 fall will bring the birds south, the wind of course being 

 northerlv. 



It has been claimed that birds do not migrate zvith the zaind. 

 This is a mistake, at least so far as central North America is 

 concerned. Birds in this region certainlv migrate north with 

 a southerh' wind and south with a northerly wind. The most 

 favorable winds for migration in the spring are from the 

 south-west or south-east, not often directly from the south. 

 In the fall our stron crest cold winds are from the north-west. 

 In both cases the birds are favored by a '■'■quartering breeze^'' 

 unquestionably the best to sail or fly by, and facilitating aerial 

 navigation to a very considerable extent. 



We can readily imagine that as food becomes scarce in 

 northern regions in the fall, the birds become restless and 

 uneasy, as has often been observed. A cold wind coming on, 



