White-fronted Goose x Barnacle Goose Anser albifrons x Branta leucopsis
Barnacle Geese are common among feral geese flocks and hybrids involving Barnacle Goose are frequently encountered. White-fronted Goose is much scarcer as a feral bird but some do occur, e.g. they were breeding at Cley (Norfolk, UK) for a number of years. A mixed pairing of Barnacle Goose x White-fronted Goose occurred at Raynham Lake (Norfolk, UK) a few years ago and were observed to be successful (per Andrew Bloomfield). A number of hybrid geese have been frequenting the area since then and at least two of these are presumed to be the offspring of this pairing.
Hybrids between Barnacle Geese and either White-fronted Goose species normally seem to be very dark-bodied - more so than either parent.
The following bird was in the same area as the ones above - and at the exact site where the White-fronted Goose and Barnacle Goose were observed to breed a few years ago. But this bird is noticeably different showing a paler belly and white feathering in the flanks. It may well be one of the same birds that has now changed its appearance. Note that the legs were a bit more strongly orange than is apparent from the first set of photos.
presumed White-fronted Goose x Barnacle Goose, Raynham Lake (Norfolk, UK), 1st April 2011
presumed White-fronted Goose x Barnacle Goose, Raynham Lake (Norfolk, UK), 10th February 2012