Monday, 20 January 2014

Swan Goose x Snow Goose

possible domestic Swan Goose x Snow Goose hybrid, or perhaps domestic Swan Goose x (Lesser White-fronted Goose x Ross's Goose hybrid) trigen, Whitlingham (Norfolk, UK), 19th June 2011 - copyright Dave Appleton
(photo ID: 0106)

I struggled with the ID of this bird for some time.  The dark 'mane' and the all black bill were clear indications of Swan Goose ancestry but the other parent was less clear.  The white-edged greater-coverts suggested Snow Goose or Ross's Goose but it was a while before I became comfortable with idea that this bird could be a domestic Swan Goose x Snow Goose hybrid, and only after much helpful input from others.  Had  I noticed that the greater coverts were long and hanging, perhaps I would have reached this conclusion earlier!

There is another possibility though.  In the same flock there is a hybrid presumed to be Lesser White-fronted Goose x Ross's Goose (you can see it in the bottom photo below).  It is perhaps possible that that hybrid bred with one of the domestic Swan Geese in the same flock, and this bird is the trigen offspring.  So, for now, the identity is still not certain.




possible domestic Swan Goose x Snow Goose hybrid, or perhaps domestic Swan Goose x (Lesser White-fronted Goose x Ross's Goose hybrid) trigen, Whitlingham (Norfolk, UK), 5th February 2011 - copyright Dave Appleton
(photo IDs: 0109-0112)




 possible domestic Swan Goose x Snow Goose hybrid, or perhaps domestic Swan Goose x (Lesser White-fronted Goose x Ross's Goose hybrid) trigen, Whitlingham (Norfolk, UK), 1st July 2011 - copyright Dave Appleton
(photo IDs: 0107-0108)



Swan Goose Anser cygnoides
Lesser White-fronted Goose Anser erythropus
Snow Goose Anser caerulescens or Chen caerulescens
Ross' Goose Anser rossii or Chen rossii

Swan Goose x (Bar-headed Goose x Snow Goose) trigen


 probable domestic Swan Goose x (Bar-headed Goose x Snow Goose hybrid) trigens, Schrevenpark, Kiel (Germany), 16th August 2011 - copyright Joern Lehmhus
(Photo ID: 0656)


These birds look a lot like domestic Swan Goose x Bar-headed Goose hybrids, but close inspection reveals some Snow Goose influence too.  The long-hanging pale-edged greater-coverts must surely be a sign of Snow Goose ancestry, but it is hard to imagine any hybrid involving just Snow Goose and one other species looking like these.

Well, Joern has a likely explanation.  There are several Bar-headed Goose x Snow Goose hybrids at this location and one of them has been associating with the flock of domestic Swan Geese rather than its own kind.  So it seems very probable indeed that these birds are the trigen offspring of a domestic Swan Goose and a Bar-headed Goose x Snow Goose hybrid.

(See also: Swan Goose x Bar-headed Goose, Bar-headed Goose x Snow Goose
 










probable domestic Swan Goose x (Bar-headed Goose x Snow Goose hybrid) trigens, Schrevenpark, Kiel (Germany), 16th August 2011 - copyright Joern Lehmhus
(Photo IDs: 0657-0666)
 












probable domestic Swan Goose x (Bar-headed Goose x Snow Goose hybrid) trigens, Schrevenpark, Kiel (Germany), 18th November 2012 - copyright Joern Lehmhus
(Photo IDs: 0553-0563)


Swan Goose Anser cygnoides
Bar-headed Goose Anser indicus 
Snow Goose Anser caerulescens or Chen caerulescens

Swan Goose x Bar-headed Goose

probable Swan Goose x Bar-headed Goose hybrid, Swanton Morley (Norfolk, UK), 25th February 2007 - copyright Dave Appleton
(photo ID: 0105)

The bird shown above and in the next two photos below shows the long sloping bill/head profile of wild-type Swan Goose along with the yellowish bill colour and light silvery body feathers that are typically found on Bar-headed Goose hybrids.  The dark crown and nape may be found on either species.  It was smaller and shorter-necked than I would have expected this hybrid to have appeared, but Joern has commented in support of this identification, pointing out that other examples of presumed Swan Goose x Bar-headed Goose hybrids have not shared the long neck that is often a feature of Swan Goose hybrids.



probable Swan Goose x Bar-headed Goose hybrid, Swanton Morley (Norfolk, UK), 25th February 2007 - copyright Dave Appleton
(photo ID: 0103-0104)


(See also: domestic Swan Goose x (Bar-headed Goose x Snow Goose))


Swan Goose Anser cygnoides
Bar-headed Goose Anser indicus

Swan Goose x Greylag Goose

wild-type Swan Goose x Greylag Goose hybrid, Bonn (Germany) - copyright Joern Lehmhus
(photo ID: 0856)


Swan Geese and Greylag Geese are the ancestors of all domestic geese and outside of the Far East the only Swan Geese you're likely to encounter are domestic variants.  Occasionally undomesticated wild-type Swan Geese can be found, at least in collections, although even if a bird looks like a wild Swan Goose it may be unsafe to assume it has no domestic heritage.  The first set of photos here show birds with long sloping bill/head profiles like wild Swan Geese and appear to be wild-type Swan Goose x Greylag Goose hybrids.



wild-type Swan Goose x Greylag Goose hybrids, Bonn (Germany) - copyright Joern Lehmhus
(photo IDs: 0854, 0855, 0857)


Hybrids between domestic Swan Geese and Greylag Geese are much more frequent.  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.

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 are too Greylag-like to be pure Swan Geese but the black on the bill, and in some the raised knob at the bill base, suggest some domestic Swan Goose ancestry.  Note that Swan Goose x Greylag Goose hybrids are fully fertile, so birds in a flock of Greylag Geese that closely resemble Greylag Goose except for a small amount of black on the cutting edge or nail may be the result of domestic Swan Goose influence two or more generations back.


domestic Swan Goose x Greylag Goose hybrid, Thetford (Norfolk, UK) 9th February 2013 - copyright Dave Appleton
(photo IDs: 0918-0919)


domestic Swan Goose x Greylag Goose hybrid, Thetford (Norfolk, UK) 19th November 2016 - copyright Dave Appleton
(photo ID: 2819)




domestic Swan Goose x Greylag Goose hybrids, Graffham Water (Camrbidgeshire, UK), 24th September 2011 - copyright Dave Appleton
(photo IDs: 0915-0917)


domestic Swan Goose x Greylag Goose hybrid, Whitlingham (Norfolk, UK) 1st January 2010 - copyright Dave Appleton
(photo ID: 0920)


domestic Swan Goose x Greylag Goose hybrid, Shcrevenpark, Kiel (Germany) 18th November 2012 - copyright Joern Lehmhus
(photo ID: 0569)



presumed domestic Swan Goose x Greylag Goose hybrids, Abberton Reservoir (Essex, UK), 21st August 2004 - copyright Dave Appleton
(photo IDs: 0921-0922)



presumed domestic Swan Goose x Greylag Goose hybrid (presumably second or subsequent generation backcross with Greylag Goose), Malmoe (Sweden), 10th June 2009 - copyright Carl Gunnar Gustavsson
(photo IDs: 0996-0997)






presumed domestic Swan Goose x Greylag Goose hybrids (presumably second or subsequent generation backcrosses with Greylag Goose), Malmoe (Sweden), 10th June 2009 (all five are different birds, and different from the photo IDs 0996-0997 above) - copyright Carl Gunnar Gustavsson
(photo IDs: 0998-1002)


presumed domestic Swan Goose x Greylag Goose hybrid (presumably second or subsequent generation backcross with Greylag Goose), Malmoe (Sweden), 13th May 2009 - copyright Carl Gunnar Gustavsson
(photo ID: 1003)


presumed domestic Swan Goose x Greylag Goose hybrid (male, presumably second or subsequent generation backcross with Greylag Goose), Malmoe (Sweden), 12th July 2008 - copyright Carl Gunnar Gustavsson
(photo ID: 1016)


presumed domestic Swan Goose x Greylag Goose hybrid (presumably second or subsequent generation backcross with Greylag Goose), Malmoe (Sweden), 26th April 2008 - copyright Carl Gunnar Gustavsson
(photo ID: 1017)




presumed domestic Swan Goose x Greylag Goose hybrid (presumably second or subsequent generation backcross with Greylag Goose), Malmoe (Sweden), 8th April 2009 - copyright Carl Gunnar Gustavsson
(photo IDs: 1019-1020)




domestic Swan Goose x Greylag Goose hybrids, Celle (Lower Saxony, Germany), 9th August 2014 - copyright Joern Lehmhus
(photo IDs: 1659-1661)


And here is the aforementioned Steinbacher, a breed of fighting goose that was developed and classified in the 1920s-30s and which has both Swan Goose and Greylag Goose in its ancestry.  Note that domestic Swan Geese and domestic Greylag Geese left to their own devices can produce birds that are identical to the Steinbacher breed, so as with other domestic waterfowl breeds the breed name shouldn't really be applied unless the pedigree is known or demostrated by further on-breeding.


domestic Swan Goose x Greylag Goose hybrids: 'Steinbacher' Geese, Hannover (Lower Saxony, Germany), 26th October 2014 - copyright Joern Lehmhus
(photo IDs: 1678-1679)


More typical domestic Swan Goose x Greylag hybrids:





domestic Swan Goose x Greylag Goose hybrid, location not given (probably Midlands/NW England, UK), on or around 9th April 2010 - copyright Steve Graby
(photo IDs: 1937-1941)



domestic Swan Goose x Greylag Goose hybrids (with domestic Greylag Geese and Canada Geese), Etherow Country Park (Greater Manchester, UK), 6th October 2010 - copyright Steve Graby
(photo IDs: 1967-1968)



Swan Goose Anser cygnoides
Greylag Goose Anser anser