[Tweeters] Broad-winged Hawk migration in Washtucna

[Brian Pendleton]

On 21 and 22 September Darchelle and I witnessed a remarkable passage of Broad-winged Hawks and Turkey Vultures through the town of Washtucna in Adams County. Around 1 PM on the 21st we were watching the willows and Russian Olives just northeast of Bassett Park under an overcast sky when at least 70 Turkey Vultures flew in from the east and began circling above us. It was a spooky experience to have so many large birds flying so low over our heads. Among the vultures were several buteos which Darchelle photographed; her photos confirmed our suspicion that they were Broad-winged Hawks. Over the next 20 minutes 63 of the vultures flew off to the southwest in three separate kettles which also included 4 Broad-winged Hawks. Turkey Vultures continued to trickle into town over the next several hours so that by 4 PM at least 40 were roosting in a large willow east of the park with a few more in other trees around town. Darchelle also photographed a fifth Broad-wing as it flew into the large cottonwood in Snyder Park.
Dense fog blanketed the basin on the morning of the 22nd becoming a low stratus layer over Washtucna by 8 AM. The sun began to break through the stratus around 9:30 AM and by 10 AM the hawks were beginning to move. A kettle of about 30 Turkey Vultures and 4 Broad-winged Hawks formed on the south side of town and began drifting off to the south. Another Broad-winged Hawk followed them a few minutes later. Around 10:45 AM another kettle formed on the northeast side of town, this one composed entirely of buteos. We identified 1 Red-tailed Hawk and 7 Broad-winged Hawks in that kettle, which we believe moved off to the southeast though we lost track of it because our attention was diverted to two additional Broad-winged Hawks which began to circle upwards in the same area at 10:50 AM. They were the last to leave as far as we know.
Darchelle attempted to photograph as many individual Broad-winged Hawks as she could, and a back-of-camera review of her photos suggests that she documented a dozen or more, at least one of which was in town on both days. She also examined almost every individual buteo through the spotting scope, distinguishing the Broad-wings from Red-tails by their tail patterns and lack of dark patagial marks and from Swainson's by their uniformly pale uderwings and more conpact shape. In kettles the Broad-wings also exhibited a characteristic flight pattern of soaring interrupted now and then by three quick wingflaps.
Although we may revise these numbers slightly after further review of our photographs, we believe that we saw a total of 18 Broad-winged Hawks in Washtucna over the two days, of which about two thirds were juveniles and two were dark-phase birds. One key assumption behind our counts is that after we watched a bird leave the area in a kettle, it did not return and get counted again. Given that several likely Broad-wings left town without our being able to verify them, and that several others may have departed undetected, the actual count could be in the low 20s.
Brian Pendleton
kc7wpd at hotmail.com
Seattle
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