Courtship Displays and Natural History of Scintillant (Selasphorus scintilla) and Volcano (S. flammula) Hummingbirds

—The natural histories of Volcano (Selasphorus flammula) and Scintillant (S. scintilla) hummingbirds are poorly known. We describe aspects of their breeding behavior with emphasis on courtship displays and sounds that males produced for females. Males of neither species sang undirected song. Males of both species produced a display dive, in which they ascended ,25 m in the air and then dove, swooping over the female. Both species produced a pulsed sound that was synchronized with abrupt tail spreads during the bottom of the dive. The second rectrix (R2) of both species was capable of generating the same sound in a wind tunnel, suggesting these sounds were made by the tail. The dive sounds of the Volcano Hummingbird were louder than those of the Scintillant Hummingbird. Male Scintillant Hummingbirds produced a wing trill in flight, and performed a shuttle display to females in which the wing-beat frequency reached ,100 Hz. Males held territories in open areas during the breeding season. Not all territories included abundant floral resources, and abundant resources in closed habitat were not defended. The role of resources is unclear in the breeding system of these two species. Received 6 May 2010. Accepted 1 December 2010. The basic natural history of most Central and South American species is poorly known, compared to North American birds. For example, of the seven species in the hummingbird clade Selasphorus, courtship displays consisting of both dives and shuttle displays have been described for Allen’s (S. sasin) (Aldrich 1938, Mitchell 2000), Rufous (S. rufus) (Calder 1993, Hurly et al. 2001), and Broad-tailed (S. platycercus) (Calder and Calder 1992) hummingbirds, as well as Calliope Hummingbird (Stellula calliope) (Tamm et al. 1989, Calder and Calder 1994), which is phylogenetically nested within Selasphorus (McGuire et al. 2007, 2009). These four species breed in the United States and Canada. In contrast, courtship displays for Volcano (S. flammula) and Scintillant (S. scintilla) hummingbirds of Costa Rica are only known from the brief descriptions by Stiles (1983), and are entirely unknown for the Glowthroated Hummingbird (S. ardens) of Panama. Members of Selasphorus and the related genera of Calypte, Archilochus, and Mellisuga perform dynamic and spectacular courtship dives (Clark 2006, Clark and Feo 2008, Feo and Clark 2010). Selasphorus and Archilochus also produce shuttle displays for females (Banks and Johnson 1961, Hamilton 1965, Hurly et al. 2001, Feo and Clark 2010). The sounds produced during these displays are either vocal (Clark 2006), or mechanically produced with their wings and/or tail (Clark and Feo 2008, 2010; Feo and Clark 2010). Male Scintillant and Volcano hummingbirds have emarginated inner rectrices (Fig. 1) that may function to produce sound during displays (Stiles 1983), and male Scintillant have an emarginated P10 that may produce a wing trill (Stiles 1983). Our objectives in this paper are to: (1) describe the courtship displays and sounds of Volcano and Scintillant hummingbirds, and (2) provide natural history observations of their breeding biology.