UI warbler, Larimer County

[Sandra Laursen]

Yesterday e saw a warbler that puzzled us in the Endovalley picnic area at Rocky Mt NP.  Distinctive features included grey wings with white bars, bright yellow breast and throat fading to a duller color on the back and tail, and bright yellow head with a definite black eye stripe. It was flitting around and feeding on some kind of insect it was finding in an aspen tree.   The song was similar to the 'swee swee' notes of a Virginia's or MacGillivray's but shorter- usually 5 repeated notes and no fading or fiddly ending.  We have scoured the books trying to identify it -  it looked a lot like the Blue-Winged Warbler but didn't sound like the recordings of that bird (and would be wildly off course ). The other warblers that make sense for the park seem to have much more grey and black than this one; the yellow was quite bold.   Suggestions?

While in the park we also enjoyed the Ring-Necked Ducks on Lily Lake and the Clark's Nutcrackers at Rainbow Curve on Trail Ridge Road.  My Australian friend was quite delighted with the Stellers Jays.

- Sandra Laursen
Boulder

[Sandra Laursen]

After some good exchanges with other CObirders off list, I feel more confident in calling this bird a Blue-Winged Warbler.  Mark Miller pointed out that a Blue-Winged Warbler loitered in a Jeffco park for several weeks in 2015, and this led me to dig through the cobirds archive to discover nearly-annual sightings of this bird somewhere along the Front Range, as well as in SE Colorado and South Park.  So this makes the RMNP Endovalley location a bit more plausible.  Two of us watched it for a good bit of time - and we feel confident about the field marks we saw.

I also found several records of 'different' songs for this bird and suggestions that (here at least) they often hang out with Yellow Warblers. I can imagine that a wandering bird (or progeny thereof) without good same-species models might pick up a song that is more like that of another locally singing species - particularly if the reason the individual is out of its usual range, or at the ragged edge, is that it is less fit to begin with.  

- Sandra Laursen

On Thursday, May 17, 2018 at 10:24:40 PM UTC-6, Sandra Laursen wrote:

Yesterday we saw a warbler that puzzled us in the Endovalley picnic area at Rocky Mt NP.  Distinctive features included grey wings with white bars, bright yellow breast and throat fading to a duller color on the back and tail, and bright yellow head with a definite black eye stripe. It was flitting around and feeding on some kind of insect it was finding in an aspen tree.   The song was similar to the 'swee swee' notes of a Virginia's or MacGillivray's but shorter- usually 5 repeated notes and no fading or fiddly ending.  We have scoured the books trying to identify it -  it looked a lot like the Blue-Winged Warbler but didn't sound like the recordings of that bird (and would be wildly off course ). The other warblers that make sense for the park seem to have much more grey and black than this one; the yellow was quite bold.   Suggestions?

[Joyce Takamine]

In June 2004 there was a Blue-winged Warbler in Gregory Canyon in Boulder which did not sing a pure  Blue-winged song.

Ted Floyd said that we could not count it as a Blue-wing since it did not sing a pure song, but I believe that some birds can

learn other songs.  Maybe Nathan could comment on that.

Joyce Takamine

Boulder

[Nathan Pieplow]

Joyce is correct; pure-looking Blue-winged and Golden-winged Warblers can sing the song of the other species. Hybrids can sing the song of either species, or (rarely) an intermediate song. Often, what people consider an "abnormal" song from one of these species may be a perfectly normal rendition of the second-category song (some people might be used to thinking of it as the "alternate" song). However, second-category songs of these two species are extremely variable and diverse, and cannot safely be identified to species as far as I am aware.

In short, song tells us little about a Vermivora warbler's parentage, and song alone should never be used to identify a Vermivora warbler to species.

Nathan Pieplow

Boulder

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