In a word no, I don't agree. There is probably a location, probably
a famous one, probably Cape May or somewhere on the Gulf Coast where
this is approximately true. But one-size-fits-all is never a
particularly useful ecological construct.

For the Columbia River Estuary and based on about 15 years worth of
observations:

Western Sandpipers- Adults late July; Juves early August
Shorebirds taken together - largest volume late-August; diversity
early September
Flycatchers- Early September
Swainson's Thrushes- Late August
Warblers- Early September
Nearctic sparrows- Mid September

Results based on protocol driven surveys and bird banding data and
represent calculated peak numbers using near-point (LOESS) regressions.
Smaller numbers of some species can be found much later in the season
(as late as early November). Weather, tide and moon phase may affect
year-to-year results. Results in your patch may vary.

--
Mike Patterson
Astoria, OR
celata at pacifier.com

SNOWY OWLS on the Lower Columbia - links to current information
on the 2005 irruption event:
http://home.pacifier.com/~neawanna/SNOW/SNOW20051120.html