Herrin? Hull 
(Larus argentatus) 
- 5 - 
126 
Undoubtedly the most common large gull found in the grid at this 
season was the Herring -lull. Despite periodic checks of the gulls 
following the shio, no species other than herring and glaucous-winged 
gulls were found doing so. This is in contrast to specific composition 
of gull populations in equivalent latitudes along the coast (where the 
California gull predominates). All the large gulls seen in the grid 
followed the ship for hours, and one distinctively marked bird was 
noted to be present for at least eight hours. The age composition of 
those following the ship averaged approximately 5>0 per cent adults and 
the rest were immatures and sub-adults* This would suggest that younger 
birds have a greater pelagic wandering tendency as the age ratio in a 
normal population would be predominately adult birds. 
Two specimens were collected. 
Black-legged Kittiwake 300 + 2 nocturnal 
( Rissa tridactyla ) 
This was the most abundant species throughout the grid during this 
survey. Density declined from north to south. Age composition was 
predominately immature birds (67 percent immatures in the northern 
third, 100 per cent im res in the is out era third). Apparently 
the grid includes a pelagic border of the range for this snecies. Deis 
is suggested both by the density distribution (see Table 2) and the 
age distribution. 
Two specimens were collected. 
Xanthus Murrelet 2 
( Bndomychura hypoleuca ) 
Two birds were sighted during the survey. 
Rhinocerous Auklet 17 
( Cerorhina monocerata) 
All sightings of this species were in the northern two-thirds 
of the grid; most were o^ swimming birds. It should be noted that 
the density figures for the alcids are not comparable to the other 
species for two reasons. First, they spend most of their time on 
the water where observations are difficult. Secondly, because alcids 
spend considerable time diving, they often go unseen. Thus density 
figures should be used as an index only within the alcid group. 
Three specimens were collected. 
Grid Summary 
As may be seen from Table 2 and the species accounts, the grid 
seems to include the pelagic range border for several bird species. 
Whether this is due to ocean currents, isotherms, or is in fact a 
