Greylag Goose x Swan Goose hybrid

Greylag Goose Anser anser x Swan Goose Anser cygnoides hybrid

Domestic geese are descended from either Greylag Goose or Swan Goose, or both. Indeed some domestic breeds of geese have both species in their ancestry and so even some "pure" breed domestic geese are technically hybrids between the two species (e.g. Steinbacher). Given the highly variable appearance of domestic geese it is often impossible to determine whether an individual bird is pure Greylag Goose, pure Swan Goose or a mix of both.

When in the wild, domestic geese will readily breed with feral Greylag Geese and backcrossed birds are frequently among feral flocks.

So far as I know, no pure Greylag Goose will have the distinctive contrasting dark 'mane' of a Swan Goose and they lack the raised knob above the bill that's a feature of many domestic Swan Geese. Most pure Swan Geese, even in their domestic forms, will retain the dark mane (unless they are white birds). Elsewhere I have previously suggested that orange on the bill may indicate Greylag ancestry, however British Waterfowl Standards (The British Waterfowl Association, 2008) seems to imply that the orange-billed domestic breed White Chinese Goose is a pure Swan Goose, so perhaps the orange bill colour can be achieved through selective breeding without any genetic input from Greylag Goose? Indeed Joern Lehmhus has confirmed that pure-looking domestic Swan Geese can sometimes show a little orange on the knob or on base of the bill. He thinks that an orange bill colour is a trait of Swan Goose but that the orange is normally hidden beneath black pigment. He likens it to Bean Geese that show a mainly black bill with a patch without black where the orange shows through. That theory makes sense to me and explains a captive but apparently pure (not domestic) Swan Goose that I have seen which showed a little orange on the side of the bill (here).

The following birds have clear evidence of Swan Goose ancestry. If it's true that pure Swan Goose (in domestic forms) can have extensively orange bills then it's not so easy to confirm Greylag ancestry but I think these examples are probably far enough outside the range of domestic variants of Swan Goose to assume some Greylag genes.

domestic Greylag Goose x Swan Goose hybrids, Grafham Water (Cambridgeshire, UK), 24th September 2011

domestic Greylag Goose x Swan Goose hybrid (rear, with Greater White-fronted Goose in front), Neary Lagoon (California, USA), 24th September 2011

domestic Greylag Goose x Swan Goose hybrid, Nun's Bridge, Thetford (Norfolk, UK), 9th February 2013

domestic Greylag Goose x Swan Goose hybrid, Nun's Bridge, Thetford (Norfolk, UK), 19th November 2016

Some more Greylag-like birds can also be hard to be sure about, but I think the extensive black on the bill of this one probably indicates Swan Goose ancestry.

domestic Greylag Goose x Swan Goose hybrid (with Mute Swans and Black-headed Gull), Whitlingham Country Park (Norfolk, UK), 1st January 2010

Among flocks of feral Greylag Geese it is often possible to find birds that look pretty much identical to normal Greylag Geese except for black on the nail of the bill, and perhaps excessively along the cutting edge. Some such birds show clear domestic traits such as a thicker bill or heavy rear end. My working assumption is that the black on the nail is evidence of Swan Goose ancestry. The mane also seems to be a shade darker.

domestic Greylag Goose x Swan Goose hybrid, Swanton Morley fishing lakes (Norfolk, UK), 7th March 2009

domestic Greylag Goose x Swan Goose hybrid, Whitlingham Country Park (Norfolk, UK), 1st July 2011

domestic Greylag Goose x Swan Goose hybrids, North Elmham Cathedral Meadows (Norfolk, UK), 7th March 2020

For comparison, here are photos of the parent species.

domestic Greylag Goose, Grafham Water (Cambridgeshire, UK), 24th September 2011 and domestic Swan Goose, Abberton Reservoir (Essex, UK), 21st August 2004

For more photos of these species follow the links below: