40 
Figure 1. Mean counts of Great Black-headed Gulls in 10-day periods from 
December 1989 to April 1990. 
Adults 
670 recorded between 15 December and 16 April. The peak (37) was at 
the end of February. After that, the decline was rapid and immature 
birds dominated the flocks. 
First-winters 
349 recorded between 8 December and 16 April. Peaked in mid-March, 
after which most of the adults had left. 
Second-winters 
138 between 16 December and 3 April. The pattern is similar to that of 
first-winters, with a peak in mid-March. 
Discussion 
Adults predominate among wintering Great Black-headed Gulls in 
Bahrain until the end of February, when they seem to leave quite 
quickly. Immatures increase throughout the winter, to reach their peak 
in mid-March. The reason for this could be that they winter farther 
11 
