BLACK-HEADED GULL 413 
poisonous sewage matter. Here they find abundance of 
food, in the form of floating refuse and offal of every 
description. 
As we watch these interesting birds serving the good 
purpose of scavengers amid such contaminated environment, 
we are led to wonder how they preserve so perfectly the 
purity of their white and delicately-tinted plumes. The 
adaptability of this species to its varied surroundings, and 
its confidence in the presence of man, at once make it one 
of the most interesting and companionable of sea-birds. 
Throughout the autumn and winter months it swarms on 
many parts of our shores; not being a pelagic species, it 
seldom wanders far from the coast-line. 
In cold weather numbers flock to the fields and fallows; 
hundreds may be seen following closely behind the plough, 
and they are remarkably astute in distinguishing the friendly 
ploughman, in whom they place the utmost confidence, 
from the lurking gunner whom they keep at a civil distance. 
I have observed these clever birds taking wing the moment 
I entered a field with a gun under my arm, though they 
had been searching for worms almost at the feet of a plough- 
man for a considerable time before. 
With the subsidence of a severe frost, Black-headed 
Gulls visit the flooded fields to devour the drowning earth- 
worms which have reached the surface as the soil softened.’ 
Indeed, during the first few days of an active thaw, the 
sea-shore in certain districts may be seen quite deserted. 
In the evening the birds return to the coast to rest. 
Flight.— The flight is buoyant, graceful, and well- 
sustained, and at times the aérial movements are of a 
highly interesting character. Now swooping, now gliding 
up and down with wide expanse of wing, until suddenly 
attracted by a dainty morsel of floating refuse, first one, 
then the entire flock hasten to the spot, and with fluttering 
wings, and feet almost treading on the surface of the 
water, each member endeavours in turn to bear off the 
prize, until swiftly pursued by its companions, it is obliged 
to let it go. The excitement begins afresh as the birds, 
with clamouring voices, make frantic efforts to secure 
the quarry, Finally, a Herring-Gull, or perhaps a Black- 
backed Gull, attracted to the scene of the disturbance, 
settles the matter by descending to the water and engult- 
1A habit indulged in by other species of Gulls. 
