Sunday, January 25, 2009

A hoary-type redpoll

At the risk of becoming the patron blogger of hopeless bird ID, here's an issue that David Sibley addressed with no less than 13 posts last winter.  Clearly there's much to be learned.  He made the point that blowing off anything but the palest of pale redpolls as a common was just as significant an error as overcalling pale commons hoaries (though both obviously are errors).

Tim called me while I was fruitlessly searching for WW crossbills in the central part of the county that he had another hoary redpoll at his feeders (he had one at his feeders about 5 years ago that I twitched while visiting Ginger's family around Christmastime).  He noted that this one was darker than the first one.  Here's today's bird:
Here's a zoom of the first photo.  I admit I didn't buy it as a hoary at first.  After studying it for a while though, it became clear that it was definitely frostier in overall color than the other redpolls.  Some of the male common redpolls had less streaked sides, but none of the females did.  Its bill is on the short end of the redpoll spectrum and the culmen does look concave in this pic.  This pic also shows some paler edges of the last scapulars; this was more visible in some of the bird's poses in the field than others.

The amount of black in the face does seem reduced, though this also varied based on pose.  You almost get the sense in the next picture of a little pinkish about the malar region.  I don't think this has much significance for sexing it; both Sibley and Pyle only mention the breast and rump as areas to look for pink.  Tim thought that the bird's flank streaking was more organized than the (male) common redpolls which demonstrated similar degrees of streaking.  I was inclined to agree.
Here's the best view of the rear, of the rump and undertail pattern:
The ground color of the rump is white.  There is dark central streaking to the last uppertail coverts, but only minimal black streaking to the rump itself.  The last undertail covert had a black central streak of medium width.  We really scrutinized the bird for other undertail streaks and had the sense that there might be a very thin one on the left, but were never certain.

For comparison here's an old photo of a female Common Redpoll:
Note the longer bill.  The last undertail covert has a wider shaft streak than our bird (you'll have to take my word for it, due to the angle of the photos that's not really apparent from the pics).  Obviously the undertail streaking is variable from bird to bird, comparison of just 2 photos in this regard is fairly meaningless.  Also I vaguely remember in one of Sibley's redpoll post he made the interesting observation that the degree of undertail streaking in common's doesn't really correlate with how dark or light the bird is overall.

Here's two pics of the adult female Hoary from Tim's house 5 years ago:

Its tail had a thin central shaft streak on the central UT covert and a very faint central shaft on the next feather to the left.

Finally here's a male Hoary from the feeding station in the Dunbar Forest in the eastern UP, one of the sort-of reliable places to look for them (I was REALLY cold, I didn't realize the soles were coming off my boots and when I squatted down to try to search for the birds with my scope I was basically in -10 degree weather with the bottom of my feet just in socks.  It was difficult to take pics as hard as I was shivering):

I think our bird is probably a first year female hoary (though fortunately I don't have to worry too much since I'm not doing a big year.  Really).  This is the age you would "expect" in a non-irruption year.  Using the scoring system on Sibley's site from the Jan 5, 2008 post, I would score today's bird an 11 or a 12 (the one from 5 years ago is probably a 13-14).  An 11 or higher would put a female bird in the Hoary range, with a couple caveats that birds get paler as the winter progresses and that the scale isn't validated to confirm species ID.  

Random redpoll rat fact I noticed while sketching birds at my feeders:  redpolls have much longer primary extension than goldfinches, having P9-P3 typically visible whereas in goldfinches it's usually just P9-P5.  I'm not sure if that's because redpolls have longer primaries or shorter secondaries, or both.  I seem to remember in longspurs that the more migratory ones (Smith's and Lapland) have more visible primaries than the other 2 since their wings are longer to allow for their longer migration.  Sibley mentioned a study that documented a redpoll banded in Michigan being recovered in Siberia (!) so clearly we're dealing with some long distance migrants.  I guess we can also conclude that Siberia is at least one place colder than Michigan in the winter.

1 comment:

col said...

Hi Matt - more on redpoll id this side of the pond here: http://www.freewebs.com/punkbirder/rolloverview.htm