Friday 21 February 2014

Greater White-fronted Goose x Red-breasted Goose

probable Greater White-fronted Goose x Red-breasted Goose hybrid, Üfingen (Lower Saxony, Germany), 26th January 2013 - copyright Joern Lehmhus
(plate ID: 0550)

Joern describes this as a small black goose, smaller than a Greater White-fronted Goose.  The cheek patch was ochre and it had white ate the base of the bill; the leg colour was greyish-fleshy, probably not fully correct on the drawing.  The underwing was all dark.  It arrived with a flock of White-fronted Geese, although Tundra Bean Geese and Greylag Geese were also in the area.

It is clearly an Anser x Branta hybrid, and Joern discussed the identity of this bird at length.  I shall attempt to summarise his deliberations. 

The dark plumage is typical of White-fronted Goose sp. x Barnacle Goose hybrids, but the cheek patch would be unusual in colour and extent for such a hybrid.

The way the cheek patch was lightest behind the eyes and got gradually darker resembled Red-breasted Goose x Barnacle Goose hybrids and also some captive hybrids Red-breasted Goose x Cackling Goose hybrids, though it cannot be either of these.  The contrasty pattern of Red-breasted goose, especially the white parts, seems to disappear in Red-breasted Goose hybrids we have seen so far (with Barnacle, Cackling and Brent Geese, all of which were relatively dark).  So Red-breasted Goose is a contender.

Joern also considered Hawaiian Goose as a candidate for the Branta parent, but notes the lack of strongly-ridged neck feathers typical of that species and at least some of its hybrids, and the dark underwing which is lacking in Hawaiian Goose.

For the Anser parent it is perhaps difficult to rule out Lesser White-fronted Goose, but Greater White-fronted Goose seems the better fit, is more likely, and of course this bird was with Greater White-fronted Geese.

Greater White-fronted Goose Anser albifrons
Red-breasted Goose Branta ruficollis

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