CALIFORNIA WATER BIRDS. 209 



Shearwaters were guided on their journey by the land is 

 shown by their conforming their course to the inward 

 sweep of the shore-hne at Monterey Bay, and by their 

 deflecting their hne of flight toward the land during dense 

 fog.* The Brandt's Cormorants breeding in the neigh- 

 borhood, and well acquainted with the surroundings, were 

 not so dependent upon the land for guidance, finding 

 their wa}^ readily in a fog over a placid sea from their 

 fishing grounds to their rookery, t 



Although the migrations in summer off Monterey are 

 extensive, they are insignificant in comparison with the 

 movements that follow in autumn. J Owing to the lack 

 of proper situations for rookeries, there was not a large 

 breeding population, § and hence there could not be ex- 

 tensive movements in birds breeding in the immediate 

 vicinity. The food-supply is temporarily very great in 

 such a thinly populated region, being far in excess of the 

 demands of the breeding colonies — a condition highly fa- 

 vorable for early southward migration. The area below 

 the line of snow and ice in winter in North America is 



" Shearwaters aud other birds habitually flying near the surface of the 

 water must from necessity migrate near the land if they desired to keep 

 in sight of it, particularly in the region of such constant fogs as the vicin- 

 ity of Monterey in summer. The coast at Pt. Santa Cruz, though moun- 

 tainous and less than twenty-five miles away, was scarcely ever discernible 

 from Pt. Piuos owing to the foggy state of the atmosphere. 



t Pelagic migration of birds, especially in its relation to isolated oceanic 

 islands, will be further considered in another paper, now in preparation. 



tThis is also the case in the smaller land birds in upper South Carolina. 

 See "Auk," vol. ix, pp. 33-39. 



^Sea birds are necessarily very local on this coast during the season of 

 reproduction owing to the isolated character of their breeding places. 

 Certain species are found associated on some islets and not on others. 

 Such distribution is probably due sometimes to lack of room, and not to 

 actual, scarcity in a species or to the physical conditions. All sea birds 

 having the same breeding range cannot find habitation at one spot, no 

 matter how favorable the situation may be. 



2ii Ser., Vol. V. ( 14 ) . June 19, 1895. 



