A seasonal decomposition of the estimated size of a penguin population at Phillip Island, Australia
H.-C. Yang A , L. E. Chambers B C and R. M. Huggins D EA Institute of Biomedical Sciences, Academia Sinica, Nankang Taipei 115, Taiwan.
B Bureau of Meteorology Research Centre, GPO 1289k, Melbourne, Vic. 3001, Australia.
C Penguin Study Group, c/– Phillip Island Nature Park, PO Box 403, Phillip Island, Vic. 3922, Australia.
D Centre for Mathematics and its Applications, Australian National University, Canberra, ACT 0200, Australia.
E Corresponding author. Email: richard.huggins@maths.anu.edu.au
Australian Journal of Zoology 53(2) 111-115 https://doi.org/10.1071/ZO04014
Submitted: 17 February 2004 Accepted: 22 December 2004 Published: 6 April 2005
Abstract
Modern non-parametric methods allow the estimation of a population size under weaker conditions than the classical methods if there are frequent capture occasions. Here a non-parametric estimate of the number of penguins occupying Summerland Beach, Phillip Island, Australia, was computed. This estimator did not assume equal catchability of individuals, did not assume a parametric form for the population size as a function of time and allowed individuals to leave and re-enter the population. The resulting estimate was then decomposed into a seasonal component and a trend component using seasonal time series models to facilitate the understanding of the changes in the population size. The estimated seasonal effects quantified the difference between the number of penguins in the breeding and non-breeding season, and the trend component indicated an increase in the population size over the period of the study. The estimates of the number of penguins are shown to be consistent with other estimates obtained from a variety of sampling methods and statistical analyses.
Acknowledgments
The raw data were collected by the Penguin Study Group and were kindly provided by the research section of the Phillip Island Nature Park.
Chao, A. , Yip, P. S. F. , Lee, S.-M. , and Chu, W. (2001). Population size estimation based on estimating functions for closed capture–recapture models. Journal of Statistical Planning and Inference 92, 213–232.
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