Saturday, December 1, 2007

Redpoll Identification

Some updates 4 and 6 December -
check out Jochen's comments and blog post here

With the predicted superflight of finches beginning to develop (1st ever Common Redpoll in New Mexico last week) more and more questions are coming up about finch identification.

Hoary Redpoll, although always less numerous than Common south of the Arctic, is probably more numerous than reports indicate. Identification is very difficult, requiring close and lengthy study, and observers are usually conservative on this ID, so lots of darker Hoarys are never even picked out, possible Hoarys are never confirmed, and lots of passing flocks are simply reported as Commons (1).

If you have a chance to study some redpolls and want to look for Hoary, here are some tips:
  1. The first step is simply to scan the group looking for a paler bird. But by just looking through a flock for paler color you will miss a lot of Hoary Redpolls. With practice you should begin to look for the specific types of paleness listed below - a "frosty" look to the upperparts or wings, a whiter breast, a pale rump, etc.
  2. Once you've found a pale redpoll, check the breast color - If it has pink on the breast it's a male (most 1st winter males have pink on the breast according to Pyle 1997), and identification of males is generally a little easier, but since males of both species tend to be paler than females, a male Common can often stand out as the palest bird in the flock. A male Hoary should look really pale. If there is no pink it's a female (or possibly an immature male), and identification will be more challenging, but since females of both species tend to be darker than the males, the fact that you've picked out a pale female from the flock is promising.
Then check details in no particular order, depending on what part of the bird you can see well, and try to make direct comparisons with birds of the same plumage type:
  • the scapulars should be paler with frosty whitish edges on Hoary
  • flank streaking should be sparse and narrow on Hoary
  • undertail coverts should be white or with only narrow streaks on Hoary (female Hoary often have narrow shaft streaks not as broad as on Commons, and male Common can have no streaks)
  • rump should be mostly white on Hoary, whiter on males (but male Commons can also have a noticeably pale rump)
  • the bill should look short and small, with fluffy nasal bristles covering the base of the upper mandible and making the forehead bulge a bit (but Commons also have tiny bills, you have to study some Commons at close range before you will feel confident using this feature)
  • The pale edges on the wing coverts and secondaries should be broader and whiter on Hoary (but this is variable in both species and, as with all of these clues, it's important to compare birds of the same sex) (2)
If most of these features line up with Hoary, I think it's safe to make the call. It's still subjective and really tough, so it's best to look at a lot of redpolls and get a sense of the variation before you start labeling them, but it looks like there may be plenty of redpolls to practice on this winter!

At this link you can see photos of a recent Hoary and accompanying Commons in Indiana by Peter Grube, showing the features well.

Good luck!

1) A reader suggests that many people are not as conservative as perhaps they should be, and simply slap the "Hoary" label on any noticeably pale redpoll. I agree, but I also think that many true Hoarys are overlooked, so it may actually be that many birds reported as Hoarys are not, but an equal or greater number of real Hoarys are overlooked!

2) Other features that have been mentioned and that might be worth watching for and testing (but many of these are very subjective and my impression currently is that these are less useful than the ones mentioned above):
  • a smaller and brighter red "poll" on the forehead of Hoary
  • less dark color on the throat and lores on Hoary: more restricted and not as dark (but appearance varies with angle of view)
  • Hoary overall larger and fluffier (but note subspecies differences in size)
  • neck appears thicker on Hoary
  • fluffy "leggings" on Hoary
  • A tendency for Hoary to raise tail when foraging on the ground
  • relatively longer tail
  • there may be subtle differences in calls, and this deserves more testing, but singling one calling bird out of a flock is usually impossible. The larger "Greenland" subspecies also may have different calls.


Seabrooke said...

Hi David,
Excellent and timely post, given the influx of redpolls beginning to come south. As a photographic complement, I thought I'd offer a link to the Tommy Thompson Park Bird Research Station's blog where they've posted side-by-side comparison photos of female Hoary and Common Redpolls, as well as side-by-sides of the two Common subspecies, banded this fall.
Keep up the great work!

Jochen said...

Hi David,
I wrote a little bit on potential pitfalls with three of the main field characters on my blog which might be of interest:
It's a lot of talk at first, so you might want to scroll down towards the end of the post.

Good birding,

Larry said...
This comment has been removed by the author.
Jochen said...

Concerning your note:

The problem arises when the identification is simplified:

pale bird = Hoary
dark bird = Common

when really, most Hoaries (females, immatures) are darker than some Commons (males) and the overall colouration might be used as a first hint to pick out obvious (male) Hoaries but is no more than just that, a hint.