The Chestnut-bellied Flowerpiercer (Diglossa gloriosissima) is a rare and small tanager, occurring at elevations above 3,000 m. It belongs to the subfamily Diglossinae (“highland tanagers”) and it is one of the 18 species in the genus Diglossa (Burns et al. 2014). This tanager has an overall black back and chest, rufous chestnut belly, and gray shoulder patch. There were no records of the Chestnut-bellied Flowerpiercer from 1965 to 2003; to this day they are known to occur in only 5 localities in Colombia : Cerro Munchique, Paramo Frontino, Cerro Paramillo, Jardin and Farallones del Citara (Restall at al. 2007).
The Chestnut-bellied Flowerpiercer overlaps in distribution with the Black-throated Flowerpiercer (Diglossa brunneiventris). Moynihan (1979) described the sympatry of these two species in the scrub and edges of forest at high altitudes, but Hilty (2011) notes they occupy mutually exclusive territories. The Black-throated Flowerpiercer has similar plumage to the Chestnut-bellied Flowerpiercer., They both have black upperparts, including the head and throat (Fjeldså 1990), but they differ in the underparts of their plumage. The Black-throated Flowerpiercer has rufous chestnut underparts except for the black throat, and the Chestnut-bellied Flowerpiercer only has rufous chestnut on the lower breast and belly (Fjeldså 1990). The Black-throated Flowerpiercer also has pale gray sides and light gray flanks (Fjeldså 1990). The Chestnut-bellied Flowerpiercer is also similar to Merida Flowerpiercer (Diglossa gloriosa). They both have black upper parts, with a rufous chestnut belly, and silvery blue shoulders. Although they are similar in appearance, their ranges do not overlap. The Merida Flowerpiercer is found from Tachira to Trujillo in Venezuela (Isler and Isler 1987).
Adult: Glossy black back, head, lores, tail, and breast. The belly, femoral tract, undertail-coverts and vent are vibrant rufous-chest-nut. Silvery-blue triangular shaped shoulder patched created by the lesser and median upperwing-coverts (Isler and Isler 1987). This species is also characterized as having a scaly forehead composed of compact, pointed-tip feathers (Vuilleumier 1969). Bill is slightly upturned, upper mandible longer than the lower and has a hooked tip. Bill is all black except for a pale blue-grey line at the base of lower mandible (Isler and Isler 1987). Sexes are similar in appearance.
Juvenile: Plumage pattern similar to adult but with overall duller colors. Dark brown back, head, lores, tail, and breast (Restall at al. 2007).
Tanagers that have been studied have either a Complex Basic Strategy or Complex Alternative Strategy (Ryder and Wolfe 2009). However, most tanagers only molt once a year (Isler and Isler 1987), and this prebasic molt likely occurs after the breeding season (Isler and Isler 1987, Ryder and Wolfe 2009). Many species have been found to breed in sub-adult plumage (Isler and Isler 987). Although a juvenile plumage is described for Chestnut-bellied Flowerpiercer (Hilty 2011), more specific information on molt and its timing is not available for this species.
Bill: black (Restall et al. 2007)
Iris: dark brown (Restall et al. 2007)
Legs: black (Restall et al. 2007)
Length, both sexes: 14 cm (5 ½ in.) (Isler & Isler 1987)
Mass, both sexes: Average: 14 g (n=2; 14 g – 14 g) (Pulgarin, unpublished data, cited in Dunning 2008)