[CT Birds] Ducks and stuff...

[David.F.Provencher at dom.com]

Paul,

Here is a very brief response to the question of duck migration timing, as
I understand it. There are several possible triggers for duck migration. It
is believed length of daylight, or angle of the sun relative to the earth,
triggers hormonal changes which in turn cause restlessness in the  birds
and then actual migration. With waterfowl there have also been cases where
mass migration days seem to have been triggered by particularly foul
weather (plenty of scope for puns there). So it isn't a case of the birds
knowing when to go or knowing what conditions are like on the migration
route or at the ultimate destination but rather mostly instinctual behavior
triggered by environmental stimulus. Of course the timing of migration can
be modified over time by changing conditions. If a species migrates over a
period of weeks and conditions change such that the early migrants meet a
high mortality rate, for instance iced in wetlands as you mentioned, then
the remaining breeders who arrive a bit later when conditions have improved
will generate a new generation of birds that tend to migrate a little
later. If on the other hand the early migrants meet a favorable environment
on arrival, they will have taken all the prime breeding sites and will tend
to be more successful than later arriving birds. This will bias the
migration period slightly earlier. The whole migration thing is truly
fascinating isn't it? And insect migration is even more intriguing.

Dave



-----------------------------------------
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.