Date:         Wed, 10 Dec 2003 16:16:35 -0500
Reply-To:     Maryland Birds & Birding <MDOSPREY@HOME.EASE.LSOFT.COM>
Sender:       Maryland Birds & Birding <MDOSPREY@HOME.EASE.LSOFT.COM>
From:         Steve Huy <Gabboon@AOL.COM>
Subject:      Re: avian migration and those pesky hummers
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Another thing to think about.  I know nothing about the proper wintering grounds for these hummers so i'll just generalize with discussion on neotrops:  It is often said that North America is the Summering ground for many migrants that disperse to larger territories to breed and raise young.  They actually are considered to return home in the winter.

Home is currently Central and South America for many species, but how long has it been home?  Home has probably been limited by the weather and related availablility of food.  What these birds currently return to as home was probably defined during the last major ice-age when temps were much colder through much of North America.  Global warming aside, as it is relatively new, things have warmed up a bit.  Isn't it about time some of these birds begin utilizing good wintering habitat?  Its only taken thousands of years for some species to figure it out.

If global warming trend continues, this may rapidly accelerate the process.  But unless we head into another ice-age I wouldn't be surprised to see northward expansion of winter ranges of many of these species.  Someone mark their calendar for a date in, say 5,000 years, and we'll revisit this issue to see if my goofy thought actually becomes reality.

Steve

<Back to Rufous Hummingbirds.  Banding records show that at least some hummers that wintered in the southeast have returned to the same yard in subsequent years.  Clearly, these birds orient themselves very well. That means they seem to be reading their compass very well.  They just don't orient themselves in the same orientation that the other Rufous Hummingbirds do.  The homing-pigeon analogy doesn't work here.  Again, I don't know enough about wintering hummingbirds but the "genetic-error" explanation seems to be at least as good an explanation as the "just-a-little-off" hypothesis.>

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