Hello, Birders. Back on Thursday evening, June 9th, Hannah and Andrew and I saw and heard a pair of apparent Eastern Warbling-Vireos at Walden Ponds, Boulder County. For now, of course, there is "officially" just the one species of warbling-vireo, referred to as Warbling Vireo, Vireo gilvus. But some ornithologists believe two species are involved, and they are generally referred to as Eastern Warbling-Vireo, Vireo gilvus, and Western Warbling-Vireo, Vireo swainsoni. An interesting question in Colorado is, How far west does Eastern Warbling-Vireo get? Does it overlap (is it "sympatric") with Western Warbling-Vireo?
On Saturday morning, June 11th, I obtained sound recordings of the male. Here are links to sound spectrograms of three songs from the bird: http://tinyurl.com/6gcxv2r http://tinyurl.com/6ztbwge http://tinyurl.com/6k77vda Note the sharp, high-pitched note at the end of each. Note also the overall singsong (up and down) phrasing, consisting of relatively pure-tone notes (i.e., relatively thin, not especially thick, squiggles). I believe that the preceding suite of audio field marks are good for Eastern Warbling-Vireo. If you see the birds, note their large size overall, their relatively large bills, and their yellower tones below, especially on the flanks. (Re: size. Eastern Warbling-Warbling Vireos are suprisingly big, closer in size to Red-eyed Vireo than to Western Warbling-Vireo.) But the visual differences are minor; the differences in song are the key points of distinction. Something to beware of out there: There are other warbling-vireos nearby, both "good" Western Warbling-Vireos, I believe, and one or two weird, intermediate, indeterminate jobs. And there's lotsa other stuff at Walden. During the course of my visits there on Thursday evening and Saturday morning, I saw and/or heard: Wood Ducks in double digits; Green Heron; Orchard Oriole; Eric Zorawowicz; Eastern Phoebes and American Dippers still under the 75th Street bridge; and little colonies of Rock Wrens and Marsh Wrens. The wrens are interesting. I don't think of Rock Wren as a summer bird for Walden Ponds, but there's a big new rock pile (quarry operation...) at the west end of the complex, and that's where they are. The Marsh Wrens have done something odd: As far as I can tell, they've bailed on Cottonwood Marsh, where they were so conspicuous in April and into early May; but there's a bunch of them farther west now, at the long pond that separates Walden Ponds proper from Sawhill Ponds. I think they may have just up and moved, for whatever reason; Marsh Wrens (and especially Sedge Wrens) are known to do such things. ------------------------------- Ted Floyd Editor, Birding Blog: http://tinyurl.com/4n6qswt Twitter: http://tinyurl.com/2ejzlzv Facebook: http://tinyurl.com/2wkvwxs ------------------------------- -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/cobirds?hl=en.
