[CT Birds] "Cerulean-Type" Black-throated Blue Warbler songs

Jack Swatt jswattbirds at snet.net
Sun Jun 11 21:12:34 EDT 2017

  I do a lot of birding in New Hampshire and have had the same experience as Don Morgan has had with the alternate song of the Black-throated Blue Warbler that sounds almost exactly like the Cerulean Warbler song.  It seems lately almost all the BT Blues I hear up there are singing this alternate song.  It's become familiar to northern birders, but frequently gets misidentified as Cerulean Warblers by people not familiar with this song, as I did when I first heard it.  Just as Don had mentioned, the BT Blues singing this alternate song respond to playback of Cerulean warbler song and not to BT Blue playbacks.  It has generated several discussions on the NH Birds list-serve about visually verifying any Cerulean Warbler observations, especially since their decline has made them very rare sightings in the state of NH
While this song has been reported in NH, VT and MA, Don's report is the first one I've heard of in CT.  I'm not sure if this is a goegraphically local song to New England, but I haven't heard of any reports outside the area (granted, I didn't do an extensive search of McCauley or Xeno-canto).  As mentioned before, in the northern states Cerulean Warbler has become quite rare, but in MA and CT their ranges overlap.  I would suggest visually confirming any Cerulean Warbler identification based on song, especially in the northern hills where the overlap occurs.  This should be especially considered when submitting sightings into eBird where the data can be used scientifically to monitor population trends.
If anyone can't open Don's recording, I also have one on an eBird checklist:
Jack Swatt

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