Michael, yes, I wonder what banding station info has to say, but it
does seem likely that there are different populations of Robins in play.
Another example might be Dark-eyed Junco that has a solid late Spring/
Summer breeding population here until dwindling away August time. This
is followed by seemingly another population descending on us late Sept/Oct.

This balanced out by the neo-trop passerines just here for one season.David

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