The reproductive biology of tropical hummingbirds has been documented and studied in only a small fraction of species relative to the great diversity of this group. Little has been written about breeding biology of hummingbirds at the Northern Andes Eastern Cordillera in Colombia. We present detailed information on the dates, nesting locations, construction materials, measurements of nests and eggs, and gonad development of adult specimens to augment the scant reproductive data available of 2 widely distributed highland hummingbirds, the Tyrian Metaltail (Metallura tyrianthina) and the Glowing Puffleg (Eriocnemis vestita). These data were obtained during collection expeditions in the high-elevation region of the Department of Boyacá, Colombia. We found 2 Tyrian Metaltail nests in February and May, and adults with enlarged gonads in August. The single Glowing Puffleg nest was found in October, adults with enlarged gonads in May and October, and a chick mortality event (possibly due to frost) in November. Nesting sites for both species were in banks where they built 2-layered cup nests. Although nest locations and construction materials were similar to what has been reported before for hummingbirds in these genera, we identified the plants of these nests' microhabitats, as well as the families and genera of liverworts, mosses, and others used as nest construction materials. The evidence of active nests and enlarged gonads of specimens collected in this study, together with observations made by previous authors, suggest that these 2 hummingbird species breed throughout most of the year at the northeastern Andes. Our data contributes to the understanding of the reproductive biology of these hummingbirds in this region.

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