Aging nestling Carnaby’s cockatoo, Calyptorhynchus latirostris, and estimating the timing and length of the breeding season

Denis Saunders,Nick Nicholls,Rick Dawson

doi:10.3897/natureconservation.12.4863

Abstract

It is important to know the age of nestling birds for many ecological and behavioural studies. Various methods have been developed for individual species; most are based on measurements of growth in wings, tarsi or heads/bills, or observations of changes in size, plumage and behaviour over time. However, techniques for aging nestlings have not been established for most avian species. This paper sets out two methods to age nestling Carnaby’s cockatoo, Calyptorhynchus latirostris, an endangered species endemic to southwestern Australia. One method is based on the physical changes in size and plumage during the 10 to 11 weeks of the nestling period, and the other on the relationship between the length of the nestling’s folded left wing and its age developed from data obtained from nestlings of known age. The estimated age of nestlings may be used to extrapolate egg-laying, hatching and fledging dates by taking the 29 days of incubation and the 76 days of the nestling period into account. The method of estimating nestling age based on length of folded left wing provides a more accurate estimate of nestling age than observations of changes in nestling size and plumage. However in situations where it is not possible to handle nestlings, the observation method should provide a reasonable basis for calculating the commencement and end of the breeding season, the length of egg-laying and nestling periods; important population parameters specified for monitoring under the species’ recovery plan.

Highlights

Knowing the age of nestlings is important for many ecological studies, including those investigating population dynamics, life histories, behaviour, longevity, conservation planning and management (Boal 1994, Wails et al 2014)
We report on the possibility of using the same techniques on the closely related, but poorly researched Baudin’s cockatoo
In order to provide those engaged in research on the species with methods to age nestlings appropriate with their authorisations, we consider two methods for aging Carnaby’s cockatoo nestlings when the hatching date is unknown; by looking at a nestling’s physical appearance, or by comparing the length of the nestling’s folded left wing against a growth curve for length of folded left wing and age developed from nestlings of known age

Summary

Introduction

Knowing the age of nestlings is important for many ecological studies, including those investigating population dynamics, life histories, behaviour, longevity, conservation planning and management (Boal 1994, Wails et al 2014). Baudin’s cockatoo occurs in the forested southwest and is believed to have declined in numbers (Department of Environment and Conservation 2008) Both species are listed as endangered under the Australian Federal Government’s Environment Protection and Biodiversity Conservation Act 1999, listed as “Fauna that is rare or likely to become extinct” in Schedule 1 of the Western Australian Wildlife Conservation Specially Protected Fauna Notice 2013 under the Wildlife Conservation Act 1950, and listed as endangered under IUCN Red List category and criteria (IUCN 2014). Both are subject of recovery plans: Cale (2003) and Department of Environment and Conservation (2012) for Carnaby’s cockatoo and Department of Environment and Conservation (2008) for Baudin’s cockatoo. Carnaby’s cockatoo has been the subject of extensive research (Saunders et al 2013 and references therein) while there is little published research relating to the ecology of Baudin’s cockatoo

Methods

Results

Conclusion