Wednesday, December 28, 2011

A December Misidentification

Dawson, Snapper, and I opted to take advantage of the beautiful weather this morning with a hike around Williams Lake.  We found a few Field Sparrows and a Winter Wren in the area where I had them Christmas morning.  A stroll down to the north shore of Williams Lake also yielded two Cackling Geese mixed in with a very large group of Canada Geese.  I've tried unsuccessfully to find this species on the lake for a while now, so I was very pleased to finally locate a couple (this was also a life bird for Dawson!).

As we were heading home, I spotted a buteo soaring very high above the lake.  There's a resident pair of Red-tailed Hawks that have bred in the area for the past two years, so, naturally, I assumed one of them was off for a morning flight around the lake.  A quick glance through my binoculars revealed something very unexpected -- a large, white tail band.

Red-shouldered Hawk

Williams Lake has a recent history of producing out of season species.  In the summer of 2009, I had a Winter Wren singing in suitable breeding habitat at least until early August and I also had two Purple Finches well into July.  Last year around this time, I had a Gray Catbird that hung around for a couple of weeks, spending the rest of the winter at The Dahlem Center (just down the street). 

In what I originally thought would be a continuation of this theme, I originally identified this bird as a Broad-winged Hawk (which should be in Central America at this time of the year) and posted it as such to a few local listservs.  Luckily, I received a few emails from very experienced birders who pointed to several field marks on this bird that point away from Broad-winged Hawk and towards the more expected Red-shouldered Hawk.

The first email from Wayne Fisher pointed out the long, lanky wings of this bird, which are very obvious in the first picture above.  As the name would indicate, this is not a field mark one would expect to see in a Broad-winged Hawk, but it is expected in a Red-shouldered Hawk, a close cousin of broadies.  And while on the topic of wing structure, one of the field marks pointed out by the second email from Skye Hass was the bulging secondaries of this bird, apparent in the picture above and below.  A Broad-winged Hawk has wings that are (more or less) uniform in width, while Red-shouldered Hawks have wider secondaries, similar to what is seen in a Golden Eagle (and, more importantly, this bird!).  Skye and Lathe Claflin also pointed out the pale crescents below the primary tips that are visible in the first photo, another shoulder field mark.

Skye also mentioned that this bird has very dark underwing coverts, much darker than is expected on a Broad-winged (visible above and below).

While I'm completely convinced that I made the wrong identification initially, I'm still a bit thrown by one field mark that this bird appears to display -- the tail band.  Both species have banded tails as adults, but Broad-wingeds have a pronounced band that appears larger than the other ones.  When I first saw this bird in the field, and when I first looked at my photographs, this was the first thing I honed in on.  Even still, after reviewing my photos in more detail, I'm a bit perplexed by the apparent size of the distal tail band on this bird.  I suppose the apparent size of the band could be an artifact of lighting, angle, and/or distance (this bird was really high), or even individual variation within the species.

At any rate, this was a really good lesson in buteo identification, and I am grateful for the comments of Wayne, Skye, and Lathe that steered me in the right direction.

No comments:

Post a Comment