Anser erythropus and its Allies. 273 
some difference of habitat, surely such birds ought to be kept 
asunder. In the ' Catalogue of the Birds in the British 
Museum/ xxvii. pp. 92-99, the three forms are treated as 
distinct species by Count Salvadori, who evidently had a 
good series of skins before him. I think that there is less 
difference between A. albifrons and A. gambeli than there is 
between A. albifrons and A. erythropus, but, if a new species, 
Anser neglectus (cf. Ibis, 1897, plate ii.) can be put in be- 
tween A. brachyrhynchus and A. segetum, all the three White- 
fronted Geese ought surely to stand also, from a separatist's 
point of view. 
Some British-killed examples of A. albifrons are very 
black indeed on the under surface, and, in fact, have little 
colour except black on the lower breast and belly. One of 
these dark examples (killed in Co. Mayo) was sent by 
Mr. Coburn to a meeting of the Norwich Naturalists' 
Society along with his A. erythropus, and another is 
particularly referred to in Ussher's ' Birds of Ireland ' 
' (p. 170) as having been shot at Baronscourt. These Geese 
may have flown across the Atlantic Ocean, and thus be 
regarded as veritable A. gambeli, or they may be hybrids. 
A. erythropus is also very black occasionally, judging from 
the plate in Breeds ' Birds of Europe,' the only representation 
of it published in this country, and one which must have 
been taken from a very black- bellied example. 
It is highly probable that A. gambeli occasionally breeds 
with A. albifrons, and A. albifrons with A. erythropus, 
hybrids being thereby produced. The authors of ^ North 
American Birds,' i. p. 450, mention a cross between A. 
gambeli and Bernicla occideiitalis, and M. Suclietet notes 
another supposed cross between A. albifrons and B. brent a 
(Ois. hybrides, p. 739) . There are other instances of Geese 
interbreeding, as at Lilford, where a White-fronted goose 
paired with a Bean gander (Zoologist, 1894, p. 214), shew- 
ing that there is nothing at all improbable in a union 
between any two of the three closely allied White-fronted 
Geese. 
The following comparative measurements begin with those 
SER. VIII. VOL. II. T 
