First description of the nest, eggs, and nestlings of White-tufted Sunbeam (Aglaeactis castelnaudii) and incubation behaviours of Shining Sunbeam (A. cupripennis) in the southeast of Peru

Abstract

ABSTRACT The genus Aglaeactis is restricted to the high Andes, from Colombia to Bolivia. The breeding biology of the Shining Sunbeam (A. cupripennis) is well-known compared with the other three species of this genus, which have relatively small ranges. In this study we present the first description of the nest, eggs, and nestlings of the Peruvian endemic White-tufted Sunbeam (A. castelnaudii), and provide novel information using thermal sensors about the incubation behaviors of A. cupripennis in the highlands of southeastern Peru. The nest of A. castelnaudii was a compact, cup-shaped nest with an inner layer composed of soft beige plant material, possibly from ferns and seeds, and an external layer of fresh moss and cobwebs, “decorated” with pieces of bark, leaves, and lichens. For A. cupripennis the first incubation off-bout started at sunrise between 05:08 and 05:23, and trips continued throughout the day for approximately 13 hrs. (n = 10 days). Nest attentiveness was 61.04% ± 3.98. The species appears to use two distinct behavioral strategies to maintain optimal nest temperatures for embryonic development. Our findings suggest that these behavioral responses during the nesting stage may contribute to this clade’s successful reproduction in high elevation habitats.