Saturday, June 20, 2015

Entering the... Week of No Migration?

Migration is stereotyped as occurring in spring and fall, with summer instead being a time of nesting activity, and winter of sedentary residence on the nonbreeding grounds. 

This is an oversimplification.  Even in the heart of winter, some species are shifting progressively south in an opportunistic fashion.  Yellow-rumped Warbler does so, and inland waterfowl are commonly recognized to progress southward from the northern states as freeze up drives them our way.  Irruptions- mass movements apparently driven by poor food conditions in the normal wintering grounds, famously of Canadian boreal finches and owls- can also be ongoing through the winter.  And before all this winter movement is concluded, the first northbound migrant Purple Martins reappear from the tropics at the tail end of January!

What about summer?  Is there a window when the last spring migrants have gone, but the first southbound fall migrants have yet to appear? 

The last of the spring migrants- notably certain shorebirds and terns- are now pulling out of Louisiana for points north.  The vanguard of southbound birds- notably certain shorebirds- might start appearing around month's end.

If any week is a candidate for Louisiana briefly becoming a migration-free zone, the next seven days are it.  But realistically, there are bound to still be migrants of some species passing through, somewhere in our borders, even this week.


If there is a week of the year

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