Friday 21 February 2014

Lesser White-fronted Goose x Ross's Goose

probable Lesser White-fronted Goose x Ross's Goose hybrid, Whitlingham Country Park (Norfolk, UK), 17th January 2011 - copyright Dave Appleton
(photo ID: 0125)


This bird had been around for a number of years and its identity is not 100% certain. I think Ross's or Snow Goose involvement is fairly clear and some Anser involvement seems fairly certain too. In most respects Ross's Goose x Lesser White-fronted Goose seems the best explanation

The small bright pink bill suggests Lesser White-front, although we might expect a Ross's Goose x Lesser White-front to show more white on the forecrown. Many captive and feral Lesser White-fronted Geese are not pure, having some (Greater) White-fronted Goose ancestry - this may be the explanation, or it may simply be that the hybrid shows less white on the head compared to either of its parents.  Joern has commented to say that he has seen similarly small amounts of white on the head for Greater White-fronted Goose x Snow Goose hybrids.

Although this bird seems to have a bit of a bulky rear end there doesn't seem to be any convincing evidence for a domestic goose involvement.  Joern has pointed out that the wing moult may be contributing to the appearance of a bulky rear end, plus of course it may be over-fed at a isite where the public feed bread to the geese.

Some of the previous discussion about this bird noted that it has some black on the cutting edge to its mandibles and a very slight 'grinning patch'.  Although still leaning towards Ross's Goose, we felt that this meant that the possibility of Snow Goose involvement was not completely ruled out.  Ross's Goose tends to lack black on the cutting edges or a grinning patch, but Joern has now uncovered a number of photos of Ross's Geese that do in fact show these features to some degree.  So it seems that this is not a good reason to doubt that Ross's Goose is involved.



probable Lesser White-fronted Goose x Ross's Goose hybrid (same bird as in photo ID 0125 above), Whitlingham Country Park (Norfolk, UK), 17th January 2011 - copyright Dave Appleton
(photo IDs: 0122-0124)



probable Lesser White-fronted Goose x Ross's Goose hybrid (same bird as in photo IDs 0122-0125 above), Whitlingham Country Park (Norfolk, UK), 5th February 2011 - copyright Dave Appleton
(photo IDs: 0115-0116)






probable Lesser White-fronted Goose x Ross's Goose hybrid (same bird as in photo IDs 0115-0116 & 0122-0125 above; with Eurasian Coot and Greylag Geese), Whitlingham Country Park (Norfolk, UK), 1st July 2011 - copyright Dave Appleton
(photo IDs: 0117-0121)



Lesser White-fronted Goose Anser erythropus
Ross's Goose Chen rossii (or Anser rossii)
Snow Goose Chen caerulescens (or Anser caerulescens)

No comments:

Post a Comment