A Study in Redpolls, Bushy Run Battlefield, Westmoreland County, PA
A pale redpoll among a flock of at least 30 Common Redpolls that has been frequenting thistle feeders at Bushy Run Battlefield
for the past two weeks or so has been the subject of some debate among western PA birders. Ultimately some consensus was reached
that the bird was frustratingly intermediate and probably best left unidentified. After a few brief and distant encounters
I had over these two weeks during which I couldn't discern much about the bird, I finally got to study it closely and
at some length on 2-Feb, and I obtained some detailed photographs.
First and foremost, I came away from Bushy Run on Saturday thinking that there may actually be two "white-rumped"
redpolls present. The flock of redpolls at Bushy Run has a way of descending on the feeders rapidly and disappearing
just as suddenly, so it is difficult to keep track of individual birds within the flock. Additionally, I have seen photos
of a Hoary-type bird taken at Bushy Run several days before I made the images below that does not appear to be the same bird.
Regardless of the truth of the "two-bird theory", this discussion centers solely around the bird I did photograph on 2-Feb.
Here it is:
The bird appears to be a female. As can be seen from this angle, the bird's undertail is nearly unmarked; in reality
there are two very thin streaks. The flank streaking is fairly sparse for a female Common Redpoll, but perhaps a bit too extensive
for a "typical" Hoary Redpoll, though it does taper off well before the undertail and fade to virtual nothingness, unlike
a typical Common Redpoll. And although not directly visible in this photo (or any that I got) the rump is slightly streaked
but not boldly so. Also of note is the overall "ground color" of the bird -- paler overall than any other bird in the flock.
The scapulars have a pale and even quality to them, and the face seems lighter overall as well. Here is another photo of the
same bird, along with a photo of a Common Redpoll in the same bush in the same light and same angle, and taken with the same
shutter speed and aperture as the pale redpoll:
Thoough subtle, the Common Redpoll's face is darker than the pale bird; even more noticeable is the darker scapular streaking
on the Common. Finally, most obvious is the more extensive streaking on the flanks of the Common, and the presence of multiple
dark streaks on the undertail coverts. It seems to me that the pale bird is safe to call a Hoary Redpoll.
Despite this, in the past, this bird would probably have been passed off as a "pale Common" by way of a long-standing rule
among birders at our latitudes of accepting only the palest and most obviously streak-free of redpolls as Hoaries. Recently,
this dogma has been put to the test by none other than David Sibley, who has written at length on his blog here
about a new approach to redpolls. Sibley asserts that while it may be correct to be conservative with Hoary ID's, it is certainly
incorrect to pass all intermediate pale redpolls off as "pale Commons". Sibley resurrects an old idea, a "character index"
based on three estimations of the amount of streaking a given bird presents, as a way to guage redpolls. (See this entry
on Sibley's blog.) When I apply my own "streakiness index" to this bird, I come up with a 4 (or 5) for the undertail, a 4
for the flanks, and a 4 for the rump. Adding up the minimums we arrive at 12, which, according to Sibley, is probably
well inside the safe range for a female Hoary and not to be dismissed simply as a "pale Common".
Here is another typical female Common Redpoll, which I would score as 2-2(3)-2 (rump again not visible, so take my word
for it), for a total of 6, obviously a Common:
Finally here is a comparison shot of a Common Redpoll and what I think is the same bird as above (though this may be
the mystery Bird #2 because the pattern of what flank streaking is visible didn't match up in my mind with the for-sure "pale
redpoll" above when I was there in the field). Note in this picture the obvious difference in ground color and scapulars,
and lack of streaking on the undertail.
Common Redpoll Gallery
I'll close this page with three of the nicer photos of Common Redpolls I made, selected specifically because they
not only show the key features of Commons, but also the incredible variability displayed by individuals of this species. With
practice and patience, it's probably possible to learn to recognize every individual in a flock of this size as unique
in the group.
|A rosy male with thick, dark flank streaks
|A less-rosy male (looks pale due to use of flash), note rump and undertail streaks
|Six distinct birds