Adult Parasitic Jaeger Jackson Reservoir

[Norm Erthal]

Yesterday Kathy Mihm-Dunning and I went northeast with on planned stop at Jackson Reservoir to see if we could find the juvenile Parasitic Jaeger reported by Chris Wood and others. We were about to leave so while Kathy was using the facilities, I scanned the lake for what I thought was one last time. To my surprise, I picked up an obvious jaeger flying across the reservoir, but lost it. We then spent two hours viewing from the north side, back to the south side and returning once again to the north side to get better looks. We would pick it up on the water and in flight multiple times over this period. It became apparent quickly that this was an adult and not the same bird from the previous day. Our conclusion was an adult intermediate phase Parasitic Jaeger. Parasitics are usually earlier in the year so back to back birds was a surprise.

It was an adult phase jaeger with a complete brown chest band, pale yellow upper chest, with the back and upper wings uniform dark brown large The noticeable wing flash, belly pale with distinct straight cutoff to brown vent, and chest band. two pointed tail streamers at least two inches as they were noticeable from a distance. The tail was concolor with back.  The vent was a slightly lighter brown than back. The bill size and shape not seen well enough to describe.  No barring was present underneath.  The contact between the edge of underwing and body was straight. We separated it from long-tailed by the presence of the chest band and the uniform dark brown upperparts, not the contrasting gray inner wing and dark primaries. The body was slimmer and not as deep as you would expect with a pomarine. A pom can have some dark color under the wing on the flanks, a less complete chest band, the browner rather than grayer coloration, A second wing flash was not apparent although at the distance it was observed, this cold have been missed. It was too distant for photos although Kathy took a few digiscope shots that are very blurred.

There was little else of note at Jackson. We later stopped at Prewitt. The west end had a good number of shorebirds with nothing too unusual.

Norm Erthal

Arvada CO