Date: 4/16/17 6:35 am From: Peter Gent <gent...> Subject: [cobirds] Fwd: Phoebes near Hygiene, Boulder Co
We spent over an hour yesterday morning at the bridge over St. Vrain Creek on Crane Hollow Road, which is about 1/2 mile west of Hygiene in north Boulder County. When we arrived, 2 Phoebes were there. There was an Eastern Phoebe which was frequently going under the bridge, so we presumed this was a female building a nest. Every time she flew, she was chased by another Phoebe, which we presumed was a male. This bird has the plumage pattern of a Black Phoebe, but the dark areas are not as black as a usual Black Phoebe, and it sang a single note Black Phoebe song. We are unsure whether this is an unusual plumaged Black Phoebe or, more likely in our opinion, a hybrid Black/Eastern. After we had been there about half an hour, we first heard the usual two note Eastern Phoebe song, and then saw east of the bridge an Eastern Phoebe making this song. We believe only the males sing, and so presumed this is a male Eastern Phoebe. Our conclusion is there are 3 Phoebes there: a pair of Easterns plus a hybrid male Eastern/Black Phoebe, which could possibly be an unusual Black Phoebe.
This situation is very similar to when the Black Phoebe first showed up at the 75th Street bridge over Boulder Creek. There was a pair of Eastern Phoebes already established there, and the Black Phoebe chased the presumed female Eastern Phoebe all the time. No nests were observed, so it is not clear whether hybridization occurred there.
Some photos of these birds can be found from Peter Burke's Cobirds message at 9:30pm last night. Thanks to SeEtta Moss for posting her and Nathan's article from Colorado Birds.