How do geese know how to fly south for the winter?

[Oscar]

How do geese know how to fly south for the winter?

– Oscar V., age 9, Huntington, New York - The Conversation - November 16, 2020

EXCERPT: "Geese have a clock in their brain that measures how much sunlight there is each day. The days grow shorter during the late summer and early fall, and that’s how geese know it’s time to get ready for the journey south. Families join together in larger flocks. Geese gorge on grains and grasses to fatten up in preparation for their journey. . . . ."

[ https://theconversation.com/how-do-gees ... +winter%3F ]