Patterns in the abundance of White-bellied Sea-Eagles (Haliaeetus leucogaster) in Jervis Bay, south-eastern AustraliaJennifer A. Spencer A C and Tim P. Lynch B
A Centre for Environmental Restoration and Stewardship, Australian Catholic University, PO Box 968, North Sydney, NSW 2059, Australia.
B Jervis Bay Marine Park, PO Box 89, Huskisson, NSW 2540, Australia.
C Corresponding author. Email: email@example.com
Emu 105(3) 211-216 https://doi.org/10.1071/MU04030
Submitted: 31 May 2004 Accepted: 10 August 2005 Published: 12 October 2005
Between 2001 and 2003, we undertook 137 boat surveys for White-bellied Sea-Eagles, to investigate the abundance and distribution in Jervis Bay, New South Wales, Australia. Adult sighting rates differed between years, being highest in 2003, and both adult and sub-adult Sea-Eagle numbers differed between seasons. High sighting rates of sub-adults each autumn (April) were thought to reflect not only the appearance of locally fledged juveniles but also an influx of immature birds (2–4 years old) from outside the study area. Although it was common to observe single adult birds and pairs throughout the year, influxes of sub-adults in autumn generally led to an increase in observed group size. The largest group of Sea-Eagles observed contained eight individuals and most groups larger than two contained both adults and sub-adults. Observability was related to age-class and behaviour, with perching behaviour common in adults but relatively rare for sub-adults. The density of Sea-Eagles, and sub-adults in particular, was highest on the undeveloped northern and southern headlands, which are military and conservation reserves, compared with the urban settlements on the western shore of the study area. Furthermore, Sea-Eagles were only observed perching in forest reserves interspersed between urbanised areas, despite the appearance of suitable perches throughout the coastal suburbs. In view of these results, we discuss the possible implications for management of Sea-Eagle habitat.
The authors thank the NSW Marine Parks Authority; R. Norriego for her assistance in developing the project in April 2001; boat drivers F. Clements and J. Brown; numerous volunteer field assistants who generously gave up their time; P. Olsen, G. Bryon, D. Breen, B. Creese, C. Gray, M. Byrne, J. Shephard, N. Mooney and one anonymous reviewer for their invaluable advice on draft manuscripts. We also thank V. Mansbridge and L. Finch for providing GIS support and data layers, and NPWS Library staff and the Macquarie University Graduate School of the Environment for assistance with literature.
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