Effects of human disturbance on productivity of White-bellied Sea-Eagles (Haliaeetus leucogaster)

Abstract

Nest productivity among the White-bellied Sea-Eagle (Haliaeetus leucogaster) population on Kangaroo Island (South Australia) was monitored over 11 breeding seasons between 1985 and 1999. Territories were assessed against standardised measures of relative isolation from human disturbance and assigned to Low-, Moderate- or High-disturbance categories. When productivity data were compared between categories, the level of disturbance was found to significantly affect fledging outcomes, with high-disturbance territories having significantly lower fledging success. Of 164 occupied territory-years, 119 (72.6%) were active and fledged 0.8 (mean) young per year. Territories with high-disturbance levels produced eggs less often (65% of territories active cf. 79% active in more isolated locations), fledged fewer young (0.5 young per year cf. 1.1), and had higher rates of nesting failure (46% cf. 13%). These results indicate that to mitigate further Sea-Eagle population decline in South Australia, site-specific habitat management prescriptions, which include buffer-zone refuge provisions, are required to minimise the effects of human activity on breeding outcomes. Such prescriptions need to take into account that, unique to South Australia, most nests are on cliffs in open coastal landscapes with little visual screening over long distance, thus refuge dimensions should be double those prescribed elsewhere for nests in tall forest habitat.

Additional keywords:

• breeding habitat refuge
• buffer zones
• cliff nests
• conservation
• core territory
• disturbance sensitivity
• endangered population
• guard-roosts
• landscape view-sheds
• management prescriptions
• productivity outcomes