NESTING AND SOCIAL ROOSTING OF THE OCHRE-COLLARED PICULET (PICUMNUS TEMMINCKII) AND WHITE-BARRED PICULET (PICUMNUS CIRRATUS), AND IMPLICATIONS FOR THE EVOLUTION OF WOODPECKER (PICIDAE) BREEDING BIOLOGY

Abstract

To understand the evolution of reproductive strategies and social behavior in woodpeckers (Picidae), it is useful to compare breeding biology between the two largest subfamilies: Picinae (true woodpeckers) and Picumninae (piculets). The piculets include four species in the Old World (Sasia, Verreauxia, and Picumnus spp.) and a recent radiation of 25 Picumnus spp. in the Neotropics; however, information about their breeding biology is limited. We studied four nests and one roost of the Ochre-collared Piculet (Picumnus temminckii) in the Atlantic Forest of Misiones and eight nests of the White-barred Piculet (Picumnus cirratus) in the Chaco region, of Argentina, and reviewed the published literature on other species of Picumnus. Cavities were excavated in dead branches and tree trunks. Entrance diameters were 2.2 ± 0.2 cm (mean ± SE) for the Ochre-collared Piculet and 2.5 ± 0.1 cm for the White-barred Piculet. In both species, both parents excavated cavities, incubated eggs, fed nestlings, and maintained the cavity clean of feces. In the Ochre-collared Piculet, incubation lasted 13 days, on-bouts were 42 ± 4 (± SE) min for females and 48 ± 7 min for males, and nest attentiveness was nearly 100% during incubation and the first 10 days after hatching. Nestling Ochre-collared Piculets hatched without feathers, their eyes and pin feathers opened on day 13, and they fledged on days 26 and 27. Nestlings of both species were fed ant larvae and other small prey. In Ochre-collared Piculets, the rate of food delivery (especially by the female) increased with nestling age. Females removed 71% and males 29% of fecal sacs. Fledgling Picumnus have dark crowns and look like adult females, which is different from Sasia, Verreauxia, and most Picinae. Unlike Picinae, Picumnus parents roost together in their nest cavity before laying, throughout nesting, and (accompanied by their offspring) after fledging. They also roost in pairs or groups when not breeding. If Old World piculets also roost socially, this trait may reflect an ancestral condition of the woodpeckers.