[CT Birds] day warbler migration?
David F Provencher
david.f.provencher at dom.com
Thu Sep 24 14:38:05 EDT 2009
Glenn, Zugunruhe (migratory restlessness) is a complex phenomenon and is now believed to occur to a much lesser degree in non-migratory birds as well as in other migratory and non-migratory organisms. One could almost wonder about humans "Spring Cleaning" no?! This "unquiet or restlessness" might be better tied to the hormonal changes and reproductive process than directly to the evolved migratory strategy, I don't know. I can't pretend to be an expert but the restlessness and the orientation may well be two separate mechanisms. I don't know if any real attempt has been made to detect increased restlessness at first light during the migratory period but it is an interesting question. While the restlessness is known to be accentuated by the occurrence of nightfall during the migratory period (which occurs of course due to length-of-daylight induced physical changes in the birds themselves), the geographic orientation and direction of movement of the birds is due to cues such as position of the sun, stars, and the orientation of the bird to the earth's magnetic field. Of course the magnetic field undergoes a polar swap every so often and indeed is undergoing changes now. What that means for migration (and the field is slowly weakening as well) in the future is just one more question in a multitude of questions concerning the future of our little blue rock.
From: Glenn Williams [mailto:gswilliams9 at yahoo.com]
Sent: Thursday, September 24, 2009 2:01 PM
To: CTBirds; David F Provencher (Generation - 4)
Subject: Re: [CT Birds] day warbler migration?
Does any of the research about zugunruhe or "migratory restlessness" show that this desire to move in the appropriate migratory direction occurs to some degree in the day as well as night in nocturnal migrants?
CONFIDENTIALITY NOTICE: This electronic message contains
information which may be legally confidential and or privileged and
does not in any case represent a firm ENERGY COMMODITY bid or offer
relating thereto which binds the sender without an additional
express written confirmation to that effect. The information is
intended solely for the individual or entity named above and access
by anyone else is unauthorized. If you are not the intended
recipient, any disclosure, copying, distribution, or use of the
contents of this information is prohibited and may be unlawful. If
you have received this electronic transmission in error, please
reply immediately to the sender that you have received the message
in error, and delete it. Thank you.
More information about the CTBirds