I provide the first description of the nest and juveniles of the Coppery Metaltail (Metallura theresiae), a hummingbird endemic to Peru. The locality of Unchog, in the elfin forest of the Carpish mountains in Huánuco, is where I found this species nesting. My descriptions are based on 4 nests found on different occasions (April 2013, January 2014, and Jul–Aug 2014). Coppery Metaltail used mainly moss, lichen, lycopodium, and twigs as materials to build their nests. I found 3 nest locations: a tree branch, creek banks, and an abandoned hut. The mean internal diameter of nests was 34.45 mm long by 42.52 mm wide (n = 4). I only measured the depth of 3 of them (mean = 33.83 mm). Metaltail eggs were white and had a mean of 12.93 by 8.3 mm (n = 2). Fledglings (n = 2) were observed in July and one of them reached up to 144% the mass of an adult. I comment on other cases of nestling obesity for different species of hummingbirds. The Coppery Metaltail selects different substrates for nesting and might reproduce throughout the year.

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