Saturday, December 12, 2009

Allen's hummingbird - a new record

Pennsylvania's first Allen's hummingbird (©Scott Weidensaul)

I was privileged to band Pennsylvania's first state record Allen's hummingbird today near Leola, Lancaster County - a healthy, beautiful adult female. This is the sixth fall/winter hummer I've banded this season, but the rest have been rufous hummingbirds - great birds, but now predictable every fall in the mid-Atlantic.

Allen's, though, was long overdue in Pennsylvania, since this native of coastal California and southwestern Oregon has been recorded a few times in neighboring states. But because the immatures and females are essentially indistinguishable in the field from rufous hummers, they are probably overlooked unless a bander is able to catch and identify the bird.

Last night, while I was speaking at the Lancaster Bird Club, one of the members mentioned a friend of hers who still had a hummingbird coming to a feeder. I asked her to have her friend call me, and this morning the phone rang. Two hours later, I was knocking at Debra Raudenbush's door. Half an hour after that, we had the hummingbird in my cage trap.

Like most of the hummingbirds I band, this one was very calm in the hand during the 10 or 15 minutes it took to band her. Once we were done, before I started shooting photos, I gave her a chance to drink from a feeder, and she lapped sugar water for two or three minutes - again, almost all hummingbirds will do this in the hand if given a chance.

Then Debra held the bird for a moment on the palm of her hand before it flew off.

(Both © Scott Weidensaul)

Allen's averages smaller than rufous, and the measurements for this bird, while on the upper end of the range for Allen's, were small for rufous. The clinchers, though, were the absence of any significant notching on R2 (the second tail feather from the center) and the very narrow R5, the outermost tail feather - 2.41mm in this bird, vs. 3.5-4mm for most of the rufous I catch.

Here's a comparison of tail feathers from three rufous I've caught in the past, and today's Allen's. (The birds regrow the feathers, which are taken as permanent voucher specimens, in a matter of weeks.) Note that while rufous may or may not have a notched R2, it always has a relatively wide R5. The Allen's had neither.

(©Scott Weidensaul)

How long will the hummer stay? It's hard to say. Debra says she's been coming to the feeder since September. Like many of the western hummingbirds, rufous and Allen's are remarkably cold-hardy, with the ability to drop into a deep, hibernation-like torpor at night to conserve energy. Although nighttime lows have been in the teens and 20s lately, that's not terribly challenging to these birds.

That said, most of them clear out of here by Christmas, and the exceptionally mild weather we had in November probably encouraged more of them to stick around later than usual. As of Tuesday, all five of the rufous hummers I'd banded this fall we still present in southeastern PA, although one had laid on heavy fat reserves, suggesting it was preparing to depart soon.

From banding and observation data, it appears most of the western hummingbirds coming through the East in fall and early winter eventually migrate to the Gulf coast region, where they overwinter. By banding this Allen's, she becomes part of a continental effort to track the evolution of a new migratory route and wintering area for this and several other species of hummingbirds.