09-16-15 Bird Field Note

09-16-15 Bird Field Note

September 16, 2015

Eric Rasmussen compiled this week's bird note. The note shows warblers, the last common poorwill trapping of 2015, songbird banding, and fall raptor migration counts.

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A Mountain Bluebird surveys the grassland for insects.

Shrubs in the floodplain teem with migrating warblers. Most of our resident Yellow Warblers left this week. Bright males (above) stand out from females or immature birds (below).

Wilson’s Warblers are secretive during the breeding season but conspicuous foragers in fall.

Orange-crowned Warblers join the feeding frenzy in floodplain chokecherries.

chokecherries. Amongst the hordes of warblers, a shy Lincoln’s Sparrow alights briefly in a willow thicket.

One of the last flycatchers to migrate is the Western Wood-Pewee.

On 9/8, we used mist nets and audio lures for a last Common Poorwill trapping session. We wanted to remove the transmitter from one bird and see if our resident birds were still here. We trapped in two poorwill territories and captured the banded male from each territory.

Both poorwills were molting. They also had growing wing and tail feathers (below). Because they will require these flight feathers for migration, our resident poorwills may need to stay for a few more weeks.

Tiny Golden-crowned Kinglet males flare their namesake feathers to show aggression. Females lack this plumage.

Like last week, we caught more Swainson’s thrushes than any other bird. Buffy eye rings help us identify the species, and light feather tips retained from juvenal plumage (arrow) indicate that this is a hatch-year bird.

We captured this female White-breasted Nuthatch at Sheep Camp. Nuthatches use their upturned bills to probe for seeds and nuts, jam them into tree bark, and hammer them open.

We started our fifth annual fall migration count this week. We recorded 403 passing raptors, an opening week record. As in previous seasons, we counted high numbers of accipiters, Red-tailed Hawks, and American Kestrels. First week totals of Swainson’s Hawks, Ospreys, and Turkey Vultures are much higher than in previous seasons.

While Dan scanned for raptors, a Mountain Chickadee rested for a moment on the brim of his hat.

In our first week, we captured three Cooper’s Hawks, one Red-tailed Hawk, and one Prairie Falcon. This year, we plan to outfit two or three large falcons, three Cooper’s Hawks, and two or three Red-tailed Hawks with GPS transmitters. We deployed our first unit on a female Prairie Falcon (below). Will will deploy transmitters on adult birds that meet minimum weight requirements.

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