FIELD AND FOREST. 97 



banks of the now narrowed streams, where their sharp roving eyes 

 still find many flowering plants which are fostered by the shade and 

 nourished by the moist earth. Here the busy pairs begin housekeep- 

 ing and soon the second nest is finished, being now placed on a bush 

 or deciduous tree ; in due time the second brood appears. 



Mr. Allen has found the nest containing young as early as March 22. 

 Commencing thus betimes, the old birds have no difficulty in seeing a 

 second brood safely out and all ready to leave for winter quarters by 

 the latter part of August. The first to arrive in spring, the males take 

 the initiative in the fall journey, leaving the females and young to fol- 

 low at their leisure. A few of the latter linger on till into September, 

 and then take a hasty departure This marked discrepancy in the 

 time of the fall migration of the sexes in favor of the males is an in- 

 teresting fact, and readily explains what other observers beside my- 

 self have been puzzled by, viz : the entire absence of adult males 

 during the latter part of August and early September in localities where 

 the females and young abounded. 



Mr. Allen informs me that this species remains in considerable num- 

 bers all winter in the gardens about Los Angelos. Southern California;, 

 then, with the peninsula of Lower California, probably forms its win- 

 ter habitat, and thus may be explained its apparent absence from Mex- 

 ico, where it is replaced at all seasons by the allied species, S. rufa. 

 The Green-backed Hummer appears to be the common representative 

 of its genus in the low valleys of California from the western slope of 

 the mountains to the coast. I say common, because a second species 

 of Selosphorus. the Rufous backed Hummer is also found in California. 

 But in the low districts and in summer when the latter birds appear to be,- 

 quite rare. Mr. Allen tells me that in all his collecting he has found 

 but three nests. 



Its arrival about San Francisco, Mr. Allen says, takes place at a 

 a much later date than that of the other bird, the time being from the 

 25th of March to the 5th of April. We know that the Rufous-backed 

 Hummer is found very far to the north, and probably the great mass 

 of the migrants pass entirely through California, using the mountains as*-. ' 

 a highway, though some perhaps remain in the high interior ranges. 

 In this way the species eludes our observer's notice. 



The S. Alleni, in contrast, seems to be absent from the region north 

 of California, and lives in the lowlands, to the exclusion of the high, 



