Emperor Goose x Ross's Goose hybrid

Emperor Goose Anser canagicus x Ross's Goose Anser rossii hybrid

This bird appeared among Norfolk's Pink-footed Goose flocks in each of the five winters 2003-2007. Although regularly misidentified as a Snow Goose by optimistic observers, it was clearly a hybrid.

The identity of this hybrid was the object of much debate but a confident consensus was reached among many competent observers that it was Ross's Goose x Pink-footed Goose and it was regularly documented as such. The assumption that Pink-footed Goose was one of its parents was presumably based on the fact that it accompanied that species - there wasn't much other reason to consider Pink-footed Goose. The non-white parts of the plumage lacked the brown tones of Pink-footed Goose and the pattern of these feathers was different: the dark sub-terminal bar on the scapulars was more distinct and had more of a point at the centre. Surely if this bird had not been with Pink-footed Geese no-one would have even considered that species as a parent. The detail was much more akin to Emperor Goose than any of the grey geese.

A number of features suggest Snow or Ross's Goose involvement. The structure and especially the bill look good for these two (or Emperor Goose); the prominent white edges to the tertials and secondaries resemble those of blue phase Snow or Ross's Geese and of course the extensive white plumage is best explained by Ross's or Snow Goose involvement. If Pink-footed Goose was a parent then the large size would perhaps favour Snow Goose over Ross's Goose, but the largest Ross's Geese are as large (including a first-winter bird that first arrived among the wintering Pink-feet in autumn 2001). The pink bill shows a dusky area towards the base which suggests Ross's Goose, but this could have come from the other parent. The size and shape of the bill is closest to Ross's Goose, though it often appeared slightly longer. The base of the bill was relatively straight, not as curved as in Snow Goose.

If we assume this bird was of wild origin, then the consensus identification of Ross' Goose x Pink-footed Goose did seem the most likely. However, with nothing to suggest Pink-footed Goose over any other grey goose, this identification should always have been regarded as tentative at best. The evidence was never overwhelming and the confidence in this identification that existed in some parts of the birding community was, in my opinion, always misplaced.

The possibility that this bird was in fact Emperor Goose x Ross's Goose was raised several years ago by Joern Lehmhus, whose opinions on hybrid goose identification should always be listened to! A significant development on the discussion about this bird's identity was an article dating back to 1979. Thanks to Joern for digging out The Journal of Heredity 70:395-400 (1979): Chromosome homology between the Ross's and the Emperor goose by R N Shoffner et al. This paper contains black-and-white photos of captive Ross's and Emperor Geese, a male and two female known hybrids between Ross's Goose and Emperor Goose as well as a further backcrossed hybrid. Two of the F1 hybrids in particular look extremely similar to the Norfolk bird. The resemblance is so close that it now seems hard to escape the conclusion that the Norfolk hybrid was indeed a Ross's Goose x Emperor Goose hybrid as Joern had suggested all along.

With Emperor Geese and their hybrids common in captivity the probability now has to be that this bird escaped from captivity. Having said that it is not inconceivable that a vagrant Emperor Goose could find its way to a Ross's Goose colony and produce hybrids, and there is some evidence to suggest hybrids may be more prone to vagrancy than non-hybrids, so perhaps there is still a remote chance it was a wild bird.

Emperor Goose x Ross's Goose hybrid, Burnham Market (Norfolk, UK), 12th November 2005

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), north of Docking (Norfolk, UK), 26th November 2007

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), north of Docking (Norfolk, UK), 8th November 2004

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), south of Brancaster Staithe (Norfolk, UK), 30th November 2004

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), south of Brancaster Staithe (Norfolk, UK), 8th November 2005

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), south of Brancaster (Norfolk, UK), 1st December 2006

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), south of Brancaster (Norfolk, UK), 24th November 2004

Emperor Goose x Ross's Goose hybrid (with Pink-footed Geese), south of Brancaster (Norfolk, UK), 9th November 2005

For comparison, here are photos of the parent species.

captive Emperor Goose, Martin Mere (Lancashire, UK), 26th December 2014 and Ross's Goose, Snettisham (Norfolk, UK), 17th March 2009

For more photos of these species follow the links below: