THE BIRDS OF THE LEA VALLEY RESERVOIRS. 181
over a period of more than twenty years, and on data placed
at my disposal by several observers. The paper is divided into
two main parts, a systematic list, which I do not propose to
read, and the present introduction, which is based thereon.
It must not be forgotten that my purpose is to present only
a list of those birds which may be said to owe their presence
to the existence of the. reservoirs of the Metropolitan Water
Board. Many other species beyond those in my list have been
identified.
The next question we ask ourselves is to what extent and
in what directions the large expanse of fresh water has affected
the avifauna of Essex. The list of birds of the small adjoining
County of Middlesex has been considerably increased by the
construction of reservoirs within its borders, yet when we come
to consider our own County we are surprised to find that, in
spite of the many unusual birds which have been identified,
not a single bird new to the County has been recorded from
the reservoirs in the Lea Valley. The reason is not far to seek.
Essex has a magnificent sea-board, where all the species of
aquatic birds and waders included in my present list had been
previously identified, some of them, although rare inland, being
more or less common on the coast. The changes, which may
be attributed to the construction of the reservoirs, are the
altered status of some species in relation to the County as a
whole, the altered inland status of species, and the additional
knowledge of overland migration which has been gained.
I have admitted 79 forms, which include fourteen passerine
birds, then single representatives of three orders in the Swift,
Kingfisher and Heron, seventeen anserine birds, the Cormorant
and Shag representing the Steganopodes, five species of Grebe,
three species of Diver, twenty-one limicoline birds, five terns,
five gulls, and two rails, the list concluding with those familiar
birds, the Moorhen and Coot.
One of the most outstanding features of the group of
passerine birds is the status of the Carrion Crow. This bird
has an uneven distribution in Essex. In the north of the
County, particularly inland, it is rare, while in the south it is
common, but the most remarkable feature of its distribution
is to be found at the reservoirs, where flocks of considerable
size may be seen daily, and as many as ninety-one have been