Thursday, 20 October 2011

Gorgeous Geese

I realise that this is really letting the side down, but I'm a birder based in Scotland and have never really got into wild goose watching. I have tried. I have sat on the bench at Aberlady at both dawn and dusk to watch the departure and arrival of the Pink-footed Geese. I have watched White-fonts and Barnacles, Brents and Beans. Two years ago to the day I spent a week on Islay with the family hoping that the magic of the barnies would enthuse not only me, but also G and the kids. Well it didn't really work out that way, so I just had to make do with ticking this cracking Cackling Goose in amongst the Barnacle Geese instead (on the assumption it is a genuine trans-Atlantic vagrant)...

On the other hand, I do quite like grilling the feral flocks of geese that are knocking around Edinburgh, checking for oddities. This week I bumped into this odd rufous-tinged Canada Goose.

I had already seen pictures of this bird on Stephen W's blog so was not too surprised to find it at Musselburgh. The unusual coloration of this bird could be the result of staining or some genetic variant. Personally, I was hoping this bird would match some of the interior forms of Canada Goose, such as Todd's, but having had a good trawl of the net I realise that this is not the case. Instead I am now swayed towards Stephen's original diagnosis, which is that the bird is showing staining. This red-brown iron oxide staining is well-known and fairly common in some forms of waterfowl such as swans and snow geese, but is apparently uncommon in Canada Geese - certainly I cannot find any individual with as extensive staining as this bird. Here is an example showing limited staining of the cheek patch, for example.

The earliest reference to an analysis of this staining dates back to 1918 (Ferruginous stains on waterfowl by Frederic Kennard Auk Vol. 35, No. 2). This study, by Kennard, concluded that red-brown staining in wildfowl was the result of iron oxide deposition on the feather surface as a result of digging for food among mud and decayed vegetation. It also noted that Canada Geese were much less likely to be stained than Snow Geese due to their differing feeding habits. (Interestingly, this Canada Goose was the only one observed feeding in amongst the Pink-feet by Stephen...) More recently the staining in Snow Geese has been shown to correlate with summer breeding and feeding origin. If this Canada is showing staining, then I wonder what its summer home is - maybe somewhere up the River Esk, which is pretty rich in iron oxide in places.

There were three other oddities in the flock at Musselburgh - Greylag x Canada Goose hybrids. I managed pictures of two of these. The left hand bird in each photo - but what a rogues gallery these pics are - hybrid geese, feral geese, herring gull, feral pigeon - surely no-one is still reading! See also Stephen W's hybrid geese.

Finally, a real wild goose. A Pink-footed Goose photographed this morning at Musselburgh. Standing on its own at the breakwater, it looked lost and out of place. Some Carrion Crows seemed to think the same, and were giving it occasional tweaks to see if it could become an easy meal. Note that one of the crows had highly leucistic or depigmented wings - how refreshing after all those geese!


welchs said...

Just read this post, interesting comments. Posted the Canada to hybridbirds as a query, three eminent experts (Dave Appleton*, C G Gustavsson** & Steve Mlodinow***) all gave varying degrees of support for the staining theory, but none supported it being a race or hybrid.

The Whoopers at the same spot have some birds which are very reddish on heads in particular, though I presume the arrived this way from Iceland. I have also seen Mutes rapidly staining reddish on the Seton Burn, which can be very reddish and presumably carries iron oxide waters from up on Blindwells, treated or not.

Finally, that Pinkfoot has been there all summer I believe, surprised it has survived...


(Hope all these links work)

Morg said...


Thanks for the links and the info. I hadn't thought of Blindwells, but that is a good suggestion. Maybe we'll see a few like this in the future now that we have a search image...

As for the Pink-foot - now that I think about it I did see one in late May at Musselburgh all on its own. Wonder if it is a genuine wild bird or not?