Tweets,

Mention of Rose-breasted Grosbeak song being "more fluid" than Black-headed
reminds me of Jon Dunn's (senior consultant for NATGEO guide and author of
Peterson's Warbler field guide) musings on separating Black-headed and
Rose-breasted by voice: "I can't tell their songs apart but their call
notes are very distinct."

I am offering this as an aid in distinguishing these two species; for those
familiar with the sharp "spik" call of a Black-headed, the Rose-breasted is
squeaky "ink" etc. Its subtle, but distinct (so I'm told). You might have
to be an Easterner to appreciate the difference!

Andy Stepniewski
Wapato WA