[Tweeters] Re: Blue-headed Vireo
davidirons20 at yahoo.com
Thu Jul 18 22:58:19 PDT 2013
Earlier this evening a friend forwarded the photos and song recording of the "Blue-headed Vireo" to us. We've looked at the photos, which are at best inconclusive, but then we listened to the song. The recorded vocalization is that of a typical Cassin's Vireo. It's much too burry for a Blue-headed, whose song is comprised of smooth non-raspy phrases. Here are a couple of sources for comparing this song to those of typical Blue-headed and Cassin's Vireos.
http://www.birdfellow.com/birds/blue-headed-vireo-vireo-solitarius (halfway down the page, click on the "listen" button)
http://www.birdfellow.com/birds/cassins-vireo-vireo-cassinii (halfway down the page, click on the "listen" button)
http://www.xeno-canto.org/browse.php?species_nr=&query=Blue-headed+Vireo This site has several recordings of Blue-headed Vireos. You can then search Cassin's Vireo and listen to a sampling of their songs as well.
As for the images, in two of them the bird is in odd positions that don't present particularly good angles for assessing the face pattern and the cheek to throat contrast and the other image is a bit too blurry to be very useful. This is a very tough time of year for trying to separate these birds by sight because it's hard to know where they are in their annual prebasic molt, which starts in July and is typically completed by August, before they migrate (Birds of North America Online). Vireos molt just once annually (essentially no prealternate molt). The wings of this birds look like there are multiple generations of feathers, so we suspect that this individual–an adult–is already well along in its prebasic molt. Note that a hatch-year bird would have much neater plumage. Since adult molt in summer on the nesting grounds, they are brightest and most colorful after the breeding season and then worn and dull by the time they return to breeding
grounds the following spring (feathers are 8-9 months old at that point). To our eyes, this bird looks like a bright Cassin's. The gray on the head is not dark enough for Blue-headed. Further, it seems a bit dingy below rather than really crisp white, another mark favoring Cassin's.
Long story made short, the appearance of the bird becomes moot once you listen to the audio recording, because the song is that of a Cassin's Vireo.
Dave Irons and Shawneen Finnegan
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