QUESTION: 
How do penguins know when to migrate?

         Third Graders at Burch Elementary School
         Tyrone, Georgia


ANSWER from Bill Fraser, Ecologist, Palmer Station, Antarctica
            Wed, 5 Feb 1997 12:27:03 -0500

    Migration time is moving right up on the penguins in the area
    and more than likely it is stimulated by a couple of things.
    One is the amount of light available, which is decreasing each
    day, and which may trigger hormonal responses telling the
    penguins to start "thinking" about moving on.  The other
    factor probably has to do with depleted energy stores.  The
    breeding penguins have been feeding 1 or 2 voracious chicks 
    a krill meal every day, and have as a result lost some of
    their own body mass.  This can be dangerous to a penguin
    facing winter, so they likely use a certain minimum body
    weight as a cue to leave the colonies and go to sea and 
    stock up for the winter.

    Bill