This Month in Photo of the Day: Animal Migration Photos

Mexican free-tailed bats spiral out of Eckert James River Bat Cave Preserve in Texas at dusk. The bats are hungry for pests like corn earworm moths—nutrition to keep milk flowing for their pups. Every spring millions of free-tails return to this cave.

See more photos from the November 2010 story "Great Migrations."

Watch Great Migrations this month on the National Geographic Channel »