For creatures that weigh barely more than a penny, hummingbirds certainly give you your money’s worth—through their metallic colors, feats of aerobatics, and pugnacious, outsized personalities. But for all their popularity, there is a lot that science still doesn’t know about the lives of even the most widespread hummingbird species. For example, what proportion of ruby-throats fly directly across the Gulf of Mexico twice a year, a nonstop trip of about 500 miles, instead of detouring around it? And why are many rufous and other western species of hummers expanding their winter range into the East and Southeast? (See “Rufous Hummingbirds Turning Up in Unusual Places,” March-April 2010.) Climate change also poses serious threats. “Scientists are finding disturbing changes to blooming times of flowers and also to arrival times of hummingbirds,” says Gary Langham, 蜜柚APP’s chief scientist. “The potential mismatch of nectar sources and hummingbirds means we must...