312 



CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



too abundantly with adults in winter for any very marked 

 failure to occur in their migration, ^ 



The presence of old birds with the young seems sufficient 

 to establish as a fact that the young are not without their 

 guidance. Ordinarily, perhaps, it may not extend beyond 

 example, especially in straggling flights; still actual leader- 

 ship sometimes, at least, appears to be exercised, as in the 

 case of the adult California Brown Pelican that directed the 

 movements of the little company of young-of-the-year,^ and 

 of the Dark-bodied Shearwater that apparently ordered a 

 flank movement in a whole column of Shearwaters.^ 



To summarize: i. Unless birds are actually in transitu, 

 their occurrence, whether early or late in the migration, 

 affords no real clue to the movements in progress — the mere 

 fact of the presence of the young alone in a locality not 

 proving that they are migrating independently of the adults. 



2. As seen in the birds in passage upon the ocean 

 off Monterey, adults inaugurate the southward migration 

 and are also present with the young in their migratory 

 movements. 



3. It seems reasonable, therefore, to conclude that the 

 young in the journey from their birthplace to the winter 

 home of the species are dependent upon the guidance of 

 the old birds who know the way because they have trav- 

 eled it. 



Cause of Migration. 



' Physical or Outward Winter with Its Failure of Food 



Cause < 



Inheritance 



f Desire for Travel 

 ^Talent for Geography 



[Psychological or Inward { f Guidance by Old Birds 



Education \ 



[Guidance by Physical Phenomena 



1 The wintering of old males in situations where females and young are wanting does 

 not indicate that the latter have been killed off, for they appear later in the northward 

 migration, the Towhee and Pine Warbler in upper South Carolina being examples. 



2 Calif. W. B. No. I, p. 188. 



3 Ibid., p. 198. 



