Yesterday, while hiking around Cat Lake near Isabella I encountered 3
singing black-throated blue warblers. Two were exclusively whisper singing;
the third did it briefly. Unlike the robin's whisper song, these birds were
singing a song identical in all respects to one of their typical songs,
except for volume. At a little over 100 feet distance from the birds I could
only faintly hear them. I'm curious if others have heard black-throated blue
warblers doing this.

Steve Wilson

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