Jack Bowling wrote:

Also, females tend to be more faithful to natal grounds
>than males.
>

I think that this varies depending on the taxon. Apparently waterfowl
females are extremely faithful in returning to the natal grounds (natal
phylopatry, not filo pastry) while the males are not. However, I do recall
that passerines are the opposite, males tend to be faithful to their natal
area while females are not. I imagine that there are many exceptions to
these generalizations however.

Some passerines are known to segregate based on sex in the winter, two
that have been well studied are the Slate-colored Junco (Junco hyemalis
hyemalis) and the White-crowned Sparrow (Zonotrichia leucophrys). I don't
have the references to these papers in case someone is interested. Many
blackbirds will segregate into single sex flocks during the winter,
particularly if there is a great size difference between the males and the
females (i.e. Great-tailed Grackles, Quiscalus mexicanus). Some birds also
appear to segregate in the winter according to age. Almost all records of
Swainson's Hawks (Buteo swainsoni) from the Pampas of Argentina are of
juvenile birds, the adults appear to stay to the north, west or south of the
Pampas. I do have the reference to that paper (Jaramillo, A.P. 1993.
Wintering Swainson's Hawks in Argentina: Food and age segregation. Condor
95: 475-479. - How's that for blatant promotion of your own work!).

Alvaro Jaramillo
Half Moon Bay, CA

alvaro at quake.net
http://www.quake.net/~alvaro/index.html