THE BIRDS OF THE LEA VALLEY RESERVOIRS. 205
The Sandwich Tern, Sterna sandvicensis sandvicensis Lath.
It has been identified on three occasions only, as follows:
one, August 29th, 1931; one, August 27th and September 25th,
1932. Mr. W. A. Wright was the observer on each occasion.
The Common Tern, Sterna hirundo hirundo L.
It has been occasionally recorded during the spring and
autumn migrations, as follows: one, May 2nd, 1908; one,
September 24th, 1921; about a dozen, March 9th, 1924, the
earliest date for the County; one, October 11th, 1924; two,
May 12th, 1928; one, August 8th-22nd, 1931; in 1932 a small
flock on September 25th, one on October 9th, and one on
December 9th; one, found dead, February 11th, 1933; it is
probable that the bird seen on December 9th, 1932, and the
one found dead on February nth, 1933, were one and the
same; three, September 13th and 14th; one September 18th,
and two, September 24th, 1933.
The Arctic Tern, Sterna macrura Naumann.
It has been recorded on one occasion only. Fifteen, adults
and immature, were identified by Messrs. R. W. Pethen and
W. A. Wright on August 22nd, 1931.
The Little Tern, Sterna albifrons albifrons Pall.
It has been recorded in one year only. Mr. K. R. Ashby
saw one at the King George Reservoir on September 12th, 17th
and 23rd, 1933. The bird of September 23rd was seen also by
the present writer.
The Black-headed Gull, Larus ridibundus ridibundus L.
It frequents the Reservoirs throughout the year. During
the nesting season it is seen in very limited numbers, but
otherwise it may be seen in flocks containing hundreds. It is
easily the most numerous gull. The huge roosting parties of
gulls, which in recent years have appeared at the King George
Reservoir during winter, are mainly composed of this species.
One of these gatherings, seen by the present writer, certainly
contained six thousand birds, but the flocks, which come in at
sunset and depart in the morning, are said at times to be very
much larger.
One, ringed near Kiel, Schleswig-Holstein, on July 6th,
1929, was recovered at the Reservoirs on February 15th, 1931.