Natural history notes of the Striped Woodpecker (Dryobates lignarius) in central Chile, with emphasis on its breeding biology

Abstract

The distribution of the Striped Woodpecker in Chile is from Coquimbo region, prov. Elqui ~ 29˚S, south to the Region de Magallanes, prov. Magallanes, just north of Punta Arenas (53˚S).  Its elevational distribution reached up to 2200 m.  Its habitat in south central Chile is mainly shrubby areas intermixed with mature trees, such as Peumos, Molles, Boldos, Quillay, Maitén, and Espinos, in drier areas used cactuses, where to nest.  In addition, the species can use introduced plants and trees for feeding and nesting.  Its breeding season started at the end of September to early December with a peak in October (63.3 %).  It is usually single brooded, however, nests found in December are suspected to be a second brood.  The nesting cavity seems to be excavated only by the male as no female were seen excavating, and excavation lasted 12 to 15 days.  The height from the ground in average was 3.15 m.  On average the cavity diameter was 41.9 mm and the depth ranged between 245-300 mm and the internal diameter between 65-70 mm.  The cavities were found mainly on dry branches or dry tree trunks, on soft fibers trees or cactuses.  The orientation of the cavity opening 45 % was SW, 27 % ENE, 15 % SE and 11 % NE, none received direct light at sunrise and early morning hours.  At least three species often attempted to usurp the Woodpecker´s nests namely the House wren, Chilean Swallow and Chilean Flicker.  The eggs when fresh were shiny white with a translucent appearance.  Its clutch size was between 3 (62.5 %) and 4 (37.5 %) eggs.  The incubation period was 13.3 (13-14) days (n = 14).  The female incubated 52.91 % of the time (n = 240).  They brooded the nestlings for 8-9 days and the female brooded 55 % of the time (n = 170).  The nestlings fledged between 27- 32 days.  The T10–90 period was 13 days and the growth constant K = 0.337.  The average body mass at hatching was 2.8 g and the maximum mass reached by some nestlings was 47 g ~ 115 % of the adult size. The nestling diet seems to be mainly Coleoptera and Lepidoptera larvae and a few soft arboreal spiders. The adults during autumn and early winter ate large quantities of fruits like Molle and Maitén. Also, throughout the season they favor domestic fruits such as medlars, khakis, pears, apples, damascus, and peaches.  Its mayor mortality was on the egg stage by failing to hatch, and 84 % of the eggs (n = 56) hatched.  Out of 47 nestlings 29.7 % perished and the cause of nestling mortality was by starvation product of nestling competition.  In all nests studied minimum one nestling perished by starvation and if there was much allochronic hatching all younger nestlings perished.  Nestlings of both genders at fledging time had red feathers on the forehead, in the male get reduced and, on the female disappeared with time.  Locally no migration was detected.