Join naturalists Vicki Powers and Ralph Terry for a walk in search of desert birds at 9 a.m., Friday, Jan. 14. Discover how plants and animals adapt to life in the desert on a hike at 10 a.m., Friday, Jan. 14. Explore the desert at night on a hike at 7 p.m., Friday, Jan. 14. Reservations are required. Learn about the life cycles of saguaro cacti on a walk at 2 p.m., Sunday, Jan. 16. Free with a park-use fee of $10 per vehicle; or $5 for pedestrians or bicyclists. Call for reservations or more information.