09-29-15 Bird Field Note

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09-29-15 Bird Field Note

September 29, 2015

Eric Rasmussen compiled this weeks bird field note. The note shows Cooper's Hawks, Yellow-rumped Warblers, and a Sharp-shinned Hawk.

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Bird Field Note 09/25/15 Compiled by: Eric Rasmussen

Black-billed Magpies impede the early morning serenity of a fox.

White-crowned Sparrows forage quickly through the understory during a migration ‘pulse’.

Yellow-rumped Warblers, sometimes called ‘butter-butts’, migrate in large flocks.

A Cooper’s Hawk is attracted to the flitting passerines in the floodplain.

The dark trailing edges on the wings and a dark tail with a broad white band identify this Broad-winged Hawk.

This week we captured more birds than any week so far (535). The Floodplain site was again the most productive, with 205 captures. For the first time this season, we captured more birds at the ridge site (180) than Sheep Camp (150). We also observed classic “pulses” of fall migration at the ridge site where we observed both the overall season high (75) and low (7) number of daily captures. A cold front moved through the region early in the week followed by stable conditions mid- to late-week.

To kick off our high pulse day at the ridge site we captured a Sharp-shinned Hawk. The yellow eyes, vertical striping on the breast and brownish color indicate a young bird, born this summer.

The Townsend’s Solitaire, a thrush, has a distinctive buffy wing patch, white outer tail feathers, and a buffy eye ring. We’ve captured more Townsend’s Solitaires in 2015 than in any other year.

The American Robin is one of the most recognizable birds in North America. We captured many at the Floodplain and Sheep Camp.

The bird below belongs to the flycatcher genus Empidonax. Despite taking many measurements, we could not identify it to species. We collected tail feathers for genetic analysis.

We recorded 970 migrating raptors this week, which brings our season total to 1,824. As predicted, we saw many Turkey Vultures; our weekly vulture total was higher than the totals of all other species combined. We expect to continue seeing high numbers of Turkey Vultures, and lower numbers of American Kestrels.

We captured 10 raptors this week: three Sharp-shinned Hawks, one Cooper’s Hawk, three Red-tailed Hawks, two American Kestrels, and one Peregrine Falcon. We outfitted one Cooper’s Hawk and two Red-tailed Hawks (below) with satellite transmitters. We have one remaining GPS transmitter to deploy on a large species like a Red-tailed Hawk, Peregrine Falcon, or Prairie Falcon.

We deployed the last of our small, nine-gram transmitters on an adult female Cooper’s Hawk.

We have GPS data on six of the seven units we’ve deployed. All six raptors have left the Bitterroot Valley. Some birds have exhibited ‘stopover’ behavior (Cooper’s Hawk 1, Peregrine Falcon, Red-tailed Hawk 1), while others continued to move south (Cooper’s Hawk 2, Red-tailed Hawk 2).

The three young Osprey from the North Center Pivot are still alive. One (green) has been at the McPhee Reservoir, near Dolores, Colorado, since September 8, while the other two (yellow and blue) have yet to settle down in a spot for longer than a day or two.

Previous Field Note

09-23-15 Bird Field Note