BIRDS OF WEST THURROCK MARSH. 263
convenient habit of taking a short cut across the promontory,
and it is thus easy for the ornithologist to get a good view of
them, particularly if a strong S.W. wind is blowing.
I once had the pleasure of noting five species in one day, viz.,
Black-headed Gull (Larus ridibundus), Common Gull (L. canus),
Herring Gull (L. argentatus), Lesser Black-backed Gull (L. fuscus),
and Great Black-backed Gull (L. marinus). This was on a
bitterly cold and boisterous day in January. Incidentally, I
would remark that the larger species of gulls appear to be more
common at Thurrock and Purfleet in January than in any
other month, and, providing that the weather conditions are
as described, it is quite a common occurrence to see a fine adult
Black-backed Gull battling its way against the wind within
twenty yards of the observer.
Towards evening (3.45 p.m. till dusk, in January), the interest-
ing spectacle of the gulls' homeward flight may be seen from this
point. High overhead they wing their way in extended wedge
formation down the river to their roosting place, the larger species
in, small parties numbering from three to a dozen, and the Black-
headed Gulls in bands which may number anything from twelve
to fifty. I am of opinion that every gull haunting the river
from Stepney to Purfleet passes over Stone Ness each evening.
I can give no estimate of their number, but the passage of
small parties is practically continuous during the period of
time mentioned.
A specimen of L. ridibundus which I examined in October
1905, contained a great number of small crustaceans (? Gammarus
sp.)
In the first week of September 1905, I observed a small party
of about a dozen Terns hovering and dipping over the water
E. of the lighthouse. The distance was too great to admit of
definite identification, but the call-note and actions of the birds
were unmistakably those of Sterna. It would be interesting to
know what they were feeding on. The Little Goby (Gobius
minutus) and the Ditch Prawn (Palaemon varians) are invariably
present in the little pools left by high tide on the saltings, hence
the supposition is admissible that these ground-loving fish and
crustaceans come to the surface of the up-flowing tide and
possibly attract the Terns.
I have personally noted the following ducks :—Mallard