Saturday, 10 September 2016

Hoary for me. The Redpoll chronicles.


By the end of the trip our hopes of catching a "snowball" deteriorated; we were particularly interested in catching one for identification purposes in case one turns up in Wiltshire - as my wise uncle once said, it would be as rare as rocking horse poo. Furthermore, before catching this bird we queried whether Mealy Redpolls had hybridised with the Arctics causing there to be a handful left, especially considering many of the birds caught beforehand shared a few pro-exilipes features and even cabaret!

I would like to take credit for the capture of this female by correctly describing it (and photographing it)
 then nudging it towards the nets: all for science!

Now in the hand we could study the bird down to minute detail. Nigel - the man with the onus of looking after Matt & I but has by far the most experience with Redpolls - began the identification process by checking its under tail coverts (utc):
As you can tell this bird's utcs are bob on: pure white with no dark shafts AT ALL. 
Here's a picture of the bird's utcs being compared to Svensson (the bible of bird ringing). 

Nigel then went to the rump:
Have a look at that; just like the utc this bird's rump was top draw. Ooooo... How much I'd like to see this in the UK. 

So what are we looking for? Like most of the this Redpoll drivel there's no exact science, yet a very white rump extending way up the birds back is ideal. Some say there's a measurement across the bird's rump can seperate it from Mealy; I'd be very tentative in accepting this thesis. The last photo should help you narrow down what age/sex this species should be. 

The question is, does it fit the bill? Both metaphorically and physically!
Of course it does! Even though the bill does look rather pointed/elongated it is well in the realms of variation, being short and deep-based. Another minor point of note are the nasal hairs that go rather far down the upper mandible, giving this sheath effect. 
One feature Nigel inputted that was of particular interest, among innumerable other things, were the leg feathers. 
One valid suggestion would be to rename it the Rough-Legged Redpoll, has a nice ring to it. At first this may not mean a lot to you since I don't know many birders staring at the Redpoll's legs. However, if you compare it to a Mealy Redpoll:
I think it's pretty self-explanatory. It also supports Darwin's theory as a side note; natural selection causing birds with more insulation to live longer and reproduce. So if you ever see a booted/rough-legged Redpoll you could be onto something. 

So now we know it's a supposed "Coues' Arctic Redpoll" what age and sex is it? Let's start with ageing. 
Tail feathers (tfs) and wing feathers (wfs) fresh and no moult break in greater coverts. Juveniles should be going through a complete now so old feathers should be being replaced by new ones and difference in colour and wear should be obvious. 

Now to sexing: Clear white rump, lack of pink in the chest eliminates possibility of a male. So there you have it: an adult female Coues' Arctic Redpoll, ladies and gentleman. 

If only it was that simple. If you have a look in the old trusty Collin's field guide and go to page 379; you should notice an illustration of a very white Redpoll with no sign of buff to the tips of the greater coverts. That description clearly doesn't fit with this bird. That's not to say the book's wrong but is showing a classic clear-cut individual, it's never that simple is it? What I'm saying is that there's far more variation than one might expect (like I did beforehand). I'm also suggesting to look more carefully at that whiter redpoll you find in the winter and not disregard simply because it isn't the snowball you might first presume. 

The question I'm waiting to be definitively answered is whether Arctic and Mealy hybridise, there's a PhD - that no one will fund you for! Did Arctic Redpoll become genetically distinct enough to prevent interbreeding (and the formation of a fertile offspring) before global warming caused a shift in the Mealy Redpoll north? All very interesting stuff, so interesting I'm planning to write my EPQ on it. Watch this space!

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