Threnetes ruckeri, Band-tailed Barbthroat. Scarce hummingbird of humid evergreen forest and edge in tropical lowlands, found from southeastern Guatemala and Belize to western Ecuador and western Venezuela. Favors shady understory with Heliconia flowers. Usually visits flowers briefly and whips away with a sharp buzzy squeak. Song is a fast 'tzi-tzi-tsee-ee-tsi-tzi-tzi'. In Costa Rica the Pacific slope population has a more complex song than that of the Caribbean slope birds; it includes…