Chloephaga sp. in Germany (escape) but which species ? (1 Viewer)

[Joern Lehmhus]

Bemerkung zur Beobachtung - www.ornitho.de

Bemerkung zur Beobachtung - www.ornitho.de

Hi all, the bird linked above was seen in Germany in recent days and first identified as a possible female Upland or Magellan goose Chloephaga picta.
It is clearly not that, due to differences in flank barring and head shape,
but either a Ruddyheaded goose Chloephaga rubidiceps or perhaps a hybrid Ruddyheaded x Greyheaded goose Chloephaga rubidiceps x poliocephala.

This hybrid has also occurred in nature in South America, but those few hybrid birds of which I have seen documentation looked a bit different. However the reduction of flank barring is stronger than in any rubidiceps I have seen ...

 

[stevethehydra]

My first, completely amateur, thought is that it looks intermediate between rubidiceps and (female type) picta, and not much like poliocephala. But that's just from looking at photos on the internet, I've only seen any of these species "in person" in captive collections!

 

[RafaelMatias]

Joern,
Upland/Magellan Goose is not an option as you say, easily ruled out by structure (overall shape, bill), and colour pattern (including the "white eye-lids"/eye-ring).
It looks like a weird Ruddyheaded (shape OK, but colour pattern off), certainly not a pure individual and thus hybrid imo. Ashy-headed is the closest structurally to Ruddy-headed Goose (same size and shape) and a cross between both would likely still have the same structure. A cross with picta would most probably have somewhat different shape. Are there more photos, showing the undertail coverts?

 

[Joern Lehmhus]

Hi Steve and Rafael thanks for your comments . yes, with Greyheaded I certainly meant Ashy-headed goose C. poliocephala.

Steve , for me there are two points to distinguish between female picta and rubidiceps (beside size difference) the head shape with a much flatter frontal part in rubidiceps than in picta as well as the finer dark flank barring in rubidiceps than in picta (in the latter the black barring is often wider than the pale barring in the rear flanks) ....
so this bird is a rubidiceps or a hybrid rubidiceps x poliocephala which is structurallly and sizewise comparable as Rafael confirms .

Rafael, I thought rubidiceps and poliocephala have the same undertail covert pattern :

https://flic.kr/p/2kNKHQT

https://media.gettyimages.com/id/1354158840/de/foto/two-ruddy-headed-geese-chloephaga-rubidiceps-swimming-on-a-pond-at-the-london-wetland-wildlife.webp?s=2048x2048&w=gi&k=20&c=JgxNmC625xeK81eMMZb3NQhYEe9merT34uYkMV_fAhY=

So what does the undertail pattern help in this case? Or do I overlook something?

I will try to find more photos of the German bird!
Meanwhile,
for comparison: photos of hybrids Ruddy-headed and Ashy-headed Goose Chloephaga rubidiceps x poliocephala from South America

https://flic.kr/p/iTVwkN

https://flic.kr/p/iTVxub

https://flic.kr/p/2aBGnHU

https://flic.kr/p/2chgtvs

Canquenes

This may be the same individual in all photos, but this is clearly is more intermediate between poliocephala and rubidiceps than the German one

 

[Joern Lehmhus]

This photo and this video is from another location in Northern Germany a few weeks earlier (and about 150 km away as the crow-or goose!-flies) , but I think it is the same bird , as it seems to have the same reduction of the barring in the foreflanks (you see that in the video)

Bemerkung zur Beobachtung - www.ornitho.de

This series is from the location I linked first (but where it appeared later) - I do not think it helps much - but maybe you can find something useful in there:

https://www.ornitho.de/index.php?m_id=54&backlink=skip&mid=935801

 

[RafaelMatias]

Rafael, I thought rubidiceps and poliocephala have the same undertail covert pattern :

So what does the undertail pattern help in this case? Or do I overlook something?

Yes, indeed they have. Sorry, my comment was not meant to suggest they'd be different. It would just be interesting to have "the full picture" of what the bird looks like, even if most likely it'll have the undertail pattern just like those two species.

 

[Joern Lehmhus]

So for me the German bird is either an aberrant rubidiceps or a rubidiceps x poliocephala cross (including the possibility of a backcross to rubdiceps- I am tending towards the latter ....

Why ?

i think the reduction of the black barring in the belly/ lower flanks resembles what we see in poliocephala

https://flic.kr/p/2mwqd3K

and in the hybrids I linked above ...

however, the general ground coloration of belly and flanks is closer to rubidiceps - but it is on the very reddish end for that species - could that also be a hint to poliocephala genes as that one has this dark reddish breast?

 

[Joern Lehmhus]

As an aside : These here seem to be Chloephaga picta x poliocephala, Upland goose x Ashy- headed goose :

https://flic.kr/p/aCcfsS

would you agree, Rafael?

 

[RafaelMatias]

Agree on all accounts, with the caveat that it is hard to be sure of the German bird parentage (some features are hard to reconcile with a F1 hybrid as you say, and so a backcross or in alternative an aberrant Ruddy-headed may be possible). Not very helpful, I know...

 

[Alexander Stöhr]

Hello,
cant contribute, but just want to say a big thank you! Excellent Jörn, Rafael and Steve!

 

[_pauls]

Agree with Alexander - cant really help but it is a very informative thread. Thanks to all contributors.