Nests, nestling growth, and parental care of the Corsican Nuthatch Sitta whiteheadi Donnees sur les nids, la croissance des poussins et les soins parentaux chez la Sittelle corse Sitta whiteheadi

Villard, P.; Thibault, J.-Claude.

Alauda 694: 465-474

2001


ISSN/ISBN: 0002-4619
Accession: 038444726

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Abstract
Breeding of hole nesting birds has been poorly studied until use of nest-boxes. The Corsican Nuthatch, endemic to Corsica island, breeds only in a hole that it excavates in dead and rotten trees, often at a height (mean=10 meters) making nests difficult to reach. For these reasons, data on eggs were restricted to Museum collections and growing of the young were not available. To study its breeding biology, we used an IR camera plug at the top of a metal pole allowing access to holes up to 11 meters. Therefore inside nest could be monitor and the day to access nestling planned. The aims of the paper are to present data on nesting holes, on nestling growth and on behaviour of both adults and young. Nests: the entrance showed different shapes mean size: 37 mm (height), 32 mm (breadth) , as the hole itself (mean deep: 122 mm, mean length: 109 mm, mean breadth: 56 mm). Bottom of nests contains wood chips, with sometimes dry pine needles and small pieces of moss, overall constituting 10-50% of the filling. Upper part of the filling was formed by hair (Mouflon, Boar), body feathers and shading bark of Birch, more or less weave making a cup containing the eggs. Vertical cracks were plug with moss or shading bark of Birch. Corsican Nuthatch rarely uses a left hole of Great Spotted Woodpecker, but takes advantages of entrance hole made by woodpecker when bark covers the trunk. Chicks' growth: six nest-contents have been studied including 24 chicks which 20 were described and measured from 2 to 5 times. Plumage development and general aspects are summarised. Respective adjustment of different parameters measured are shown. Length of wing (1a) and of the bill (1b) grow regularly, whereas length of tarsus (1c) is stabilised at day 12th. Weight (1d) grows regularly to reach a plateau and a small inflexion before fledging. Since day 11th, a head cap appears, black or grey according to birds, suggesting a sexual dimorphism, as in adults. Young fledge at mean age of 20 days (19-22 plus or minus 1, n=28 for 7 nests). Comparatively to adults, their wing, tail and bill were significantly shorter, whereas tarsus and weight were similar. Behaviour: only females incubated the eggs, being fed by males (3.2 times/hour). Both parents fed young, but until day 8th, females also brood young. During the last week of rearing, head of young appeared at the entrance hole, getting finally head outside during several seconds the day before fledging. Male song's activity occurred through the breeding but more active during incubation, it decreased during rearing. The last males cease to sing during the first half of July, when range of adults and fledglings around nest site increased.