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
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
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
