Further Information about the Nest, Eggs and Nestlings of the Copper-Rumped Hummingbird Saucerottia tobaci from Venezuela

Abstract

The Copper-rumped Hummingbird Saucerottia tobaci is a polyphyletic hummingbird with seven recognized subspecies. Nonetheless, the most information on its nesting behavior come from the island race S. t. erythronotos. This study aims to describe a nesting event of S. t. feliciae, the most widespread mainland subspecies, in order to provide detailed information on its nest structure, eggs and nestling development, as well as report information related to the nesting success (survival strategies, potential threats), based on observations carried out from August to October 2021 in northern Venezuela. Features of nest (composition, form, dimensions), eggs (appearance, dimensions, mass) and nestling development data from hatching to fledging time (body length, bill, wings, tail, and body mass) were all recorded in detail. The nest was an open saddle-type, cream in color, built of silky vegetable down, silky fibers of moth cocoon, mossy stuffs, pieces of lichen and spider’s web. Nest dimensions (mm): outer-cup depth: 40.7; inner-cup depth: 18.0; base-bed: 22.7; cup-rim thickness: 10.0–12.0; cup-rim length: 40.4; cup-rim wide: 18.4. Two oval-shaped eggs were laid inside, white in color, without spots or blots, smooth in texture, and non-glossy. Egg mass (0.6 ± 0 g; n = 2), egg length (13.95 ± 0.07 mm; n = 2), egg width (9.4 ± 0.14 mm; n = 2). Both eggs were incubated during 16 days. Nestlings were born almost completely naked, dark skin above, reddish beige below; bill yellow with the tip red and blunt; eyes closed. Nestling body mass at hatching (0.6 ± 0 g, n = 2), fledgling period (23 days). First feather barbs (day 10), eyes open (day 10), nestling totally feathered (day 16), and nestling body mass at fledging (4.7 g, n = 1). Survival strategies were nest camouflage, roof protection, female motionlessness, distraction displays and mobbing behavior. The nest was also close to a bumblebee nest and an artificial feeder. Potential threats included nest predators and heavy rains. This study introduces novel information on nesting behavior of a mainland subspecies and suggests that S. t. feliciae resembles S. t. erythronotos with slight differences in terms of nest construction, and eggs mass and length. Data on other nests, including those of other Venezuelan subspecies, are necessary to fully categorize the nesting behavior of this hummingbird in order to identify critical subspecific elements (e. g. nest materials, nestling´s food, human impact, additional nest predators and parasites) needed for its conservation in future.