2o8 CALIFORNIA ACADEMY OF SCIENCES. 



waves were sometimes immediate forerunners of large 

 ones. Individuals apparentl}^ preceded the first waves of 

 northern species. Usually a large wave extended over 

 several or more days, beginning gradually, reaching a 

 day of maximum height, and then subsiding, being fol- 

 lowed by a period when little migration took place in the 

 species. With the progress of migration these lulls gen- 

 erally became of shorter duration, and were marked by 

 increasing numbers of birds temporarily pausing by the 

 way, resting upon the water or flying about at random. 

 When a number of species were migrating at one time, 

 it did not uniformly happen that the height of migration 

 occurred upon the same day in each, for often the waves 

 of some were waning while those of others were waxing. 

 The California Murre typically exemplified early south- 

 ward migration in species breeding in the region and the 

 Northern Phalarope in species breeding in boreal regions. 



" Barren birds " did not play an important part in the 

 migrations, and young birds of the year did not precede 

 the adults. In some instances young birds were found 

 accompanying the adults, as in the Marbled Murrelet on 

 July 31st. Such young birds, weak of wing, drop by the 

 way, furnishing seeming instances of prior occurrence of 

 young birds during the early movements of species into 

 regions south of their breeding habitats.* 



It has been seen that the Dark-bodied Shearwater, a 

 highly pelagic species, followed the coast-line in migrating 

 in the same manner as the Northern Phalarope. That the 



* The mere occurrence of the young in a given locality before the pres- 

 ence of adults has been detected proves nothing beyond the bare fact that 

 young birds were observed there earlier than adults. It does not prove 

 that they left the region of their birth in advance of their parents, any 

 more than the habitual absence in a locality of a species breeding to the 

 northward and wintering to the soiathward of it, proves that the species 

 does not migrate. 



