Subject: 'sexually driven' migration pattern (Was: Robins)
Date: Nov 6 08:24:55 1995
From: Serge Le Huitouze - serge at cs.sfu.ca


JLRosso at aol.com writes:

> I am very interested in "sex-segreated migration". I will never forget
> showing some slides of a trip to mexico where I photographed a
> Yellow-bellied Sapsucker. I was surprised to see the sapsucker down
> there. Alan Baldridge of Monterey casually mentioned that the female
> Yellow-bellied Sapsucker migrated further south than did the male. I
> was amazed that he had this eclectic bit of information which he
> casually tossed out, but I was also intrigued that there would be
> such a mechanism. Why would sexes of the same species migrate in
> different ways? How would that have evolved? What would be the advantages
> of doing this?
>
> I can sort of understand why adults might migrate earlier
> than juvenilles....
>
> But differences between the sexes in matters of migration is
> most intriguing.

It is also the case in many birds that the males will migrate before the
females (in the beginning of the breeding season) so as to establish
territory before females arrive.

I think a species where males and females would migrate different distances
in the winter, with the male (or more precisely the "displayer") travelling
the shortest distance) would just make the above mentionned behaviour even
more easily achieved.

I think this happens with some birds of the shore (ducks and shorebirds??),
as well as in somes songbirds.
The (European) Chaffinch _Fringilla coelebs_ has been given his scientific
name by Linnaeus because of its winter behavior: in Sweden, males were
(they still are :-) the only Chaffinches seen in winter, the females
going further south. Linnaeus came up with "coelebs", which means "bachelor"
(or "unmarried"), as the species name...
Isn't it a nice story?
(more to come on scientific names in a few weeks... Stay tuned...)


P.S.
Sorry, I talked about birds today, I must be sick :-)

--
--------------------------------------------------
"Come to think of it, there are already a million monkeys on
a million typewriters ... and Usenet is NOTHING like Shakespeare..."

Serge Le Huitouze Intelligent Software Group
email: serge at cs.sfu.ca School of Computing Science
tel: (604) 291-5423 Simon Fraser University
fax: (604) 291-3045 Burnaby, B.C., V5A 1S6 CANADA
http://www.isg.sfu.ca/~serge/