GULLS AND TERNS. 21 
of this species that are sometimes witnessed are 
chiefly due to such accidental causes as an 
unwonted supply of food, or a continued spell of 
boisterous weather, which often drives Gulls in 
thousands into sheltered bays and estuaries. This 
Gull is generally met with beating about in a 
solitary manner ; less frequently three or four may 
be seen together; whilst even in the breeding 
season, when most Gulls congregate into colonies 
whose size seems only to be regulated by the 
accommodation presented, it is certainly the least 
sociable of all the British species. It is a great 
nomad during the non-breeding season, often 
wandering far from land, resting and sleeping on 
the sea. On the other hand, it is one of the least 
frequent visitors of the Gull-tribe to inland districts, 
and, as its specific name of martnus indicates, 1s 
closely attached to the sea. The usual call-note of 
this fine Gull is a loud, whining, oft-repeated ag- 
ag-ag. Notwithstanding the purity of its plumage, 
and the magnificence of its presence, the Great 
Black-backed Gull is almost as unclean in its 
habits as the Raven or the Vulture. No kind 
of carrion is refused, either lying on the shore or 
floating on the sea—weakly, death-stricken lambs 
or wounded birds, eggs or chicks left unguarded 
by their owners, fish basking or sleeping near the 
surface, offal cast from the fishing boats or quays, 
animal refuse of all kinds, form the prey of this Gull. 
The usual breeding place of this Gull is the top 
