Re: Swainson's thrush
- In my experience, the delay in vocalizing with already late-arriving
Swainson's thrushes is more characteristic of western than eastern populations. And
I don't know any thrushes -- or any other neotropical summerers -- with such
a striking pattern of delay. Male black-headed grosbeaks, for instance, arrive
one morning and begin pretty much full song the next. Most of our warblers
sing as they filter north, at least once they're in the States.
The Swainson's pattern plays out in reverse as they prepare (early) to leave
for the south: several weeks before they actually take flight one evening,
they begin their night-migration call in the early morning hours.
There is no more striking example than this species that the neotropicals
are not "our" birds at all, but simply brief summer visitors.
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