SOUNDS AND COURTSHIP DISPLAYS OF THE PERUVIAN SHEARTAIL, CHILEAN WOODSTAR, OASIS HUMMINGBIRD, AND A HYBRID MALE PERUVIAN SHEARTAIL x CHILEAN WOODSTAR

We describe the songs and courtship displays of three closely related hummingbirds, the Peruvian Sheartail (Thaumastura cora), Oasis Hummingbird (Rhodopis vesper), and the endangered Chilean Woodstar (Eulidia yarrellii). The Peruvian Sheartail and Oasis Hummingbird sing complex multisyllabic songs, while the Chilean Woodstar's song is monosyllabic and simple. Like North American bee hummingbirds (within the tribe Mellisugini), the Chilean Woodstar and Oasis Hummingbird perform stereotypical close-range shuttle displays and larger display dives. The Peruvian Sheartail also performs shuttle and dive displays but their kinematics are variable and they are less distinct from each other. The greatly elongated tail of the Peruvian Sheartail is split widely during display, such that the five rectrices (R1-R5), including R1 and R2 of each side of the tail, project laterally, apparently as a visual signal. Like most other bee hummingbirds, all three species produce sounds during their display dives with their three outer rectrices, R3, R4, and/or R5, although the Peruvian Sheartail's sound is both faint and not produced exclusively during displays. We diagnose an adult male hybrid Peruvian Sheartail x Chilean Woodstar and describe its songs and displays. The hybrid had unique tail morphology with an elongated R2, R3, and R4, and both R1 and R4 were transgressive, longer than those of either parent species. The hybrid was from the Azapa valley, where the Peruvian Sheartail is now common and the Chilean Woodstar rare; hybridization may represent an Allee effect arising from the recent crash of the Chilean Woodstar's population.