Abstract

Observations of breeding White-throated Needletails Hirundapus caudacutus using nestboxes in Japan showed that birds utilised the vertical internal walls of the nestbox for resting and roosting. Nestlings moved from the nest at the base of the nestbox at the age of about 30 days and spent the following 3.5 weeks before fledging clinging to the walls of the nestbox. Our observations suggest that one function of the ‘needles’ in the tail of this and related species is to support and anchor the bird while it clings to vertical surfaces. Nestlings had longer needles than adults, perhaps an adaptation to the prolonged period they spend clinging to the side of the nest walls prior to fledging.