Saturday, 31 December 2016

Common or Coues's; that is the question.

I caught a frosty looking Redpoll the other day (30th) and while some people may say it is just a Common (Mealy) Redpoll there was something about it that made me think it could be a Coues's Arctic Redpoll. It is not what you would call a 'classic' Coues's by any means but then there is no such thing and when the term 'classic' is used people really mean 'easy', 'obvious' or 'most likely to be accepted'. The most readily accepted Coues's are the very pale (snowball) examples that have extensive, unstreaked white rumps but such birds are usually adults, often males and are not representative of the species as a whole.

Anyway back to the bird in question and it is important to say that it is a first year bird, based on the shape of the tail feathers, and possibly a male as there was a slight pinkish wash on a few of the feathers of the rump. Now I am not going to rhyme off all the reasons why I think it could be a Coues's, or perhaps I should say Coues's type now that research has shown there is essentially no genetic difference between Lesser, Common and Coues's, but relevant comments accompany some of the images.

It certainly had the feather mass and ability to fluff-up its feathers as you would expect with a 'Coues's Arctic'. The dense feathering of the nape and the sides of the neck also gave it a bull-necked appearance.
The sharply pointed tail feathers made it easy to age as a first year bird.

Spot the pink. There are a few feathers on the rump that have very slight pink tones and while this suggests it is a male such a limited amount of pink makes that far from certain. There was no pink (concealed or otherwise) on any of the feathers of the breast or the cheeks. 

The rump is one of the critical features and while the unstreaked area is not as extensive as on some Coues's it still falls within the range of streaking that can be displayed.

A slight change of angle and lighting and the head looks even paler. The limited flank streaking is set against a pure white ground colour.

That puffed-up look again. While there is some streaking in the rump the ground colour of the rump and lower back is pure white.

The streaking on the underparts was fairly light and ill-defined and confined to the sides of the upper breast and a narrow zone along the flanks. The streaking on Common Redpolls is usually much heavier and well defined, not diffuse and relatively fine as on this bird.

The bill was fairly stubby and conical. The eye also looked relatively small which is also a feature of Coues's.

The culmen was straight if not ever so slightly concave. The extensive and dense feathering around the base of the bill is also suggestive of Coues's. The green plant material stuck to the bill is interesting and suggests it has been feeding on the seeds of herbage rather than tree seeds. It certainly hasn't spent much, if any, time feeding on alder as it would have brown tar like deposits running in the other direction across the base of the bill. I am not suggesting this is diagnostic in any way but Coues's is a bird of the tundra and perhaps feeds more commonly on ground plants than other Redpolls.

There was some faint and very diffuse streaks on 3 of the undertail-coverts. Light streaking on a few feathers is not uncommon in Coues's (especially first year birds and females) but is unusual for Common (Mealy) Redpolls (except for a few adults, usually males). 

Such faint streaks would be virtually if not impossible to see in the field. I had to separate the feathers slightly to show that there were three marked feathers as only one was noticeable when the feathers were in their normal alignment, with that being the faint streak on the longest undertail-covert.
So what is it? Well it is...... ummm, one of them isn't it - not easy and not straightforward. There simply isn't a clear cut divide in appearance between Common and Coues's so a bird like this will always be controversial to some degree but that doesn't mean it should be called a Mealy because it is the 'safer' option. As the late Martin Garner put it 'Calling a bird a Mealy Redpoll when it is really an 'intermediate'/possible Coues's should be a bookable offence!' Some of his later writings suggested he had become much more confident about identifying streaky Coues's and again as Martin put it 'Most Arctic Redpolls are streaky. Really. They are. Which is annoying as they are supposed to be nice and plain and white in redpoll folk lore. It's often subtly different kind of streaking, but they are often streaky, even some adult males. Streaky is OK.'

So what a way to end my ringing in 2016. This was the last bird caught in the last ringing session and literally came in the last minute of extra time..... and it certainly is one of them, isn't it?

There is tons of stuff on the web about the identification of Coues's Arctic (Hoary) and Common (Mealy) Redpolls and some I found useful can be found by clicking on the following links:

Identification of Arctic Redpolls carduelis hornemanni exilipes, British Birds

Arctic Redpoll Carduelis hornemanni exilipes an identification review based on the 1995/96 influx, British Birds

Intermediate Arctic Redpoll, Birding Frontiers

Arctic Redpoll and Mealy Redpoll, Change the ID Culture, Birding Frontiers

Urging caution when identifying Common Redpolls, Sibley Guides Notebook

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