When: Early to mid-March. Where: Mission San Juan Capistrano, CA. What: Every year around St. Joseph's Day, March 19, flocks of cliff swallows return to the 230-year-old mission for the summer, nesting within the crumbling, picturesque Spanish arches. Tip: Once the birds build their distinctive nests, they're not too difficult to photograph inside them. Also look for mud spots, where the social birds meet to gather material for their nests. For info: www.missionsjc.com; 949-234-1300.