[mou] Migration window?

[Pastor Al Schirmacher]

Which species that frequents WI and/or MN has the longest migration window?

By window I mean the differential between the earliest arriving migrants and 
the latest to leave - by migration I mean leaving WI and/or MN completely at 
some point - and obviously the window does not include nesting activity.

My guess is that it would be a shorebird of some kind - since there are 
June/July "fall" arrivals, and some hangers-on linger until November, 
but....

Al Schirmacher
Princeton, MN
Mille Lacs & Sherburne Counties