ZooL.— Vol. II.] LOOMIS— CALIFORNIA WATER BIRDS. 315 



Inheritance} — Instinct and heredity have been convenient 

 words on the pens of authors deahng with aspects of migra- 

 tion in which the facts were partially or wholly unknown. 

 It is not unreasonable to suppose that there exist in migra- 

 tory birds an inherent desire for travel and an "inherited 

 talent for geography." The ease with which birds find 

 their nests in the chaparral or in a sea of tules manifests 

 that they possess memory of direction and locality in a 

 remarkable degree. In migratory birds this faculty may 

 attain higher development, becoming a talent for geography. 

 The restlessness sometimes displayed in seasons of migra- 

 tion by wild birds reared in captivity is perhaps indicative of 

 an inward incentive for travel. But here heredity seems to 

 end and 



Education to begin, for there appears to be guidance by 

 old birds and guidance by physical phenomena. With edu- 

 cation of the young into a knowledge of the way, the magic 

 words instinct and heredity lose their potency. Intelligence 

 and habit remain to account for the constancy of migratory 

 birds to time and place. We cannot know whether a bird's 



1 ".strong home affection," desire for procreation, physiological requirements as to 

 temperature during reproduction, have been advanced by some writers as paramount 

 causes in the return migration. 



The short stay of some birds at their nesting homes in temperate climates (less than 

 three months) and the variation in different years in the location of the home, as in the 

 Dickcissel, discredit the theory of " strong home affection " as a factor in migration. 



Desire for procreation, which exists in sedentary as well as migratory species, may 

 be a prompting influence, as the waning of the breeding season appears to be in the 

 opposite migration. However, the early summer movements toward the equator mani- 

 fest that there are deeper incentives. 



While the climatic conditions of the Cold Temperate Subregion may be more con- 

 genial than those of the Warm Temperate to such species as the Blackburnian Warbler, 

 it remains to be fully established that these birds can not rear their young with equal 

 success, so far as mere temperature is concerned, in any part of their habitat. Being 

 migratory species of wide range, they are accustomed to great extremes in temperature, 

 and it may be that their present distribution is simply an outgrowth of the adjustment 

 of population to food areas — each species in process of time having found a place, which 

 it holds independent of peculiar conditions of temperature. Thus is it explained why 

 some Yellow Warblers breed in South Carolina and others on the Arctic coast; why some 

 Robins winter in the valleys of the White Mountains and others in Florida; why the 

 Parasitic Jaegers visiting the South Temperate Zone recross the equator; why the Orange- 

 crowned Warblers wintering in the South Atlantic States return to the region to the 

 westward of the Alleghanies instead of seeking a nesting home on the Atlantic Slope. 

 Still it is not denied that physiological needs as to temperature during reproduction may 

 be an additional incentive to migration; but above and behind this are fundamental 

 causes, for migration exists without such stimulus, as is particularly evidenced by the 

 early summer movements toward the equator in temperate regions. 



