°8q4 J Loomis on Birds of Chester County, South Carolina. 11^ 



exceptional movements, can only be surmised. It is not too 

 much to sav that there is a common stock of knowledge, gained 

 in the past and transmitted from generation to generation, that 

 all adult birds possess. 1 



The stubbornness with which Warblers, etc., venture north in 

 spite of freezing weather is not to be attributed, I think, to lack 

 of intelligence, for it is not the cold of autumn followed by the 

 dearth of winter that they encounter, but the brief cold spells of 

 spring preceding the warmth of approaching summer with its 

 abundance of food. Mere cold does not seem to have the effect 

 that cold storms of wind and rain have, for hosts of Warblers 

 endure freezing weather at the north late in May with apparent 

 impunity (see Grundtvig, B. N. O. C, VIII, p. 67). The 

 movements cannot be delayed until all obstacle is removed, 

 because of numbers and lack of time. Then, too. there must be 

 a definite time of starting, which, as has been seen, is as soon as 

 territory is available for occupancy. The necessity of occupying 

 all available territory is evident, so it happens that fall move- 

 ments are delayed in mild seasons and advanced ground in 

 winter, temporarily habitable, is taken possession of. 



Physiological restlessness on the approach of the breedino- 

 season has been advanced as a cause of northward migration, 

 but it apparently leaves unexplained the early winter movements. 

 Further no such reason can be assigned for summer migration 

 southward (though an opposite one might be"), yet its inception 

 occurs with the utmost regularity. Still it is not denied that the 

 nuptial passion may exist when the knife does not reveal it, for it 

 is not dormant even in south-bound transients in September and 

 October. Neither is it altogether denied that desire for procrea- 

 tion may in a manner be a prompting influence in northward 

 migration. It can hardly, however, be a paramount cause, 

 independent of other causes, for it exists in sedentary species as 

 well. 'Home affection' has also been put forward as the cause 



1 The following instance of young Passenger Pigeons succumbing to an emergency 

 which old birds overcame is reported by Mr. Brewster on the authority of a Michigan 

 Pigeon netter. "On one occasion an immense flock of young birds became bewil- 

 dered in a fog while crossing Crooked Lake and descending struck the water and 

 perished by thousands. The shore for miles was covered a foot or more deep with 

 them. The old birds rose above the fog, and none were killed" (Auk, VI, p. 289). 



