HETEROCHROSIS IN ESSEX BIRDS AND THEIR EGGS. 197
Complete partial 0
Partial . . .. 0
Total . . 1
Ref.: The Birds of Essex (Christy).
Red-legged Partridge. Alectoris r. rufa (L.).
Complete .. 1
Complete partial 1
Partial . . .. 0
Unplaced .. 8
Total .. 10
Ref.: The Field, vol. 52, p. 381.; The Essex Nat., vol. 22, p. 320.
The species known to have been affected by albinism reach
the figure of 48, whereas melanism is represented by 6 and of these
two, Bullfinch and Redwing, were probably the results of cap-
tivity. Melanism would seem to operate somewhat along the
same lines as albinism and we find each of our three adopted cate-
gories represented. The information at our disposal is so
limited as to make it difficult to form conclusions. The fact that
eight out of a covey of nine Red-legged Partridges were melanistic
(The Field, v. 52, p. 381) draws attention, as this suggests the
probability that they were congenital examples.
UNPLACED ABERRATIONS.
Mute Swan. Cygnus olor (Gm.). Four Polish Swans have been
obtained. This variety was at one time separated under the
name of Cygnus immutabilis. It is stated that it has a less
developed tubercle and ash-grey legs and feet. Ref.: The
Field, vol. 100, p. 970; A History of the Birds of Essex; The
Essex Nat., vol. 23, p. 20.
Red-legged Partridge. Alectoris r. rufa (L.).
One killed near Braintree on 20 October, 1908, by Mr. A. W.
Ruggles-Brise and presented by him to the British Museum, is
described as the first example of the most extraordinary colour-
variation of this species known to occur. It has the fore-part of
the head, eye-brow stripe, cheeks and throat black, the rest of
the plumage dull vinous red, a little browner on the belly and