Hi Tweets,

It's light-duration and/or angular position of sun rather than food
availability that triggers southbound migration in the female and juv Rufous
Hummingbirds. The adult males are usually long gone, leaving when the
females begin incubating. Maintaining a feeder up to, say, the end of
October--by which time the Rufous migration is over--will do nothing more
than provide a good meal to a hungry and thirsty traveller. Any bird which
stays after that will be in nearly all instances a Rufous too sick or
injured to resume migration, or an Anna's Hummingbird. Since the virtually
non-migratory Anna's Hummingbirds cannot survive the average northern
Cascadian winter without feeder help, they turn the decision to feed them
throughout the winter into a conscious commitment.

Michael Price The Sleep of Reason Gives Birth to Monsters
Vancouver BC Canada -Goya
mprice at mindlink.net