Within Australian, it would be rare to find someone who does not know of the Wedge-tailed eagle, and rightly so with it being Australia's largest bird of prey. However, jump down just one spot to the second largest bird of prey that shares the skies above our great country and many people are unaware of this species, the White-bellied sea eagle, Haliaeetus leucogaster. The species is a large raptor that can reach up to 4.2 kg for females and 3.7 kg for males with a wingspan up to 220 cm. The plumage of the adult birds is largely white and grey with the head, breast and belly being white (hence the name). Juveniles differ quite markedly from the adults, with more mixed patterning of brown and cream plumage on the underside (see image of a juvenile below - taken on Faure Island, Western Australia). The juveniles colouration gradually transitions until they acquire the full adult plumage usually by their fourth year.
The White-bellied sea eagle is widespread around Australia (generally located not far from the coast) but is not without threats. The species is listed on the Marine species list under the EPBC Act, Vulnerable in New South Wales and Tasmania, Threatened in Victoria, and Endangered in South Australia. Threats present for the White-bellied sea eagle include indirect/secondary poisoning, shooting, wind turbine collisions and electrocution, competition with the Wedge-tailed eagle, & degrading water quality in inland waterways, however, the two major threats for the species are loss of habitat, and disturbance of nesting pairs through human activity. A study published in 2011 by Dennis et al. explored the potential impacts of humans on the nesting success of White-bellied sea eagles. Territories were assigned categories based on the disturbance levels, with productivity data (e.g. eggs produced, young fledged, nesting failures) assessed between the various categories of disturbance. Territories that were rated as high-disturbance produced less eggs than those in low-disturbance areas, 65% active compared to 79% respectively. Of these active nests success rates were also alarmingly different, with only 54% of active nests in high-disturbance areas being successful, compared to 87% within the low-disturbance areas. The frequency of this success also varied with high-disturbance areas only being successful every 2.9 years compared to every 1.5 years in low-disturbance areas. Several management recommendations have been published in various reports, including the protection of habitat on public land, identifying nesting sites prior to development including clearing of land or forestry operations, identifying human causes of breeding failure and implementing mitigation against these, further research into the diet of the species due to the potential for heavy metal accumulation, and implementing buffer zones for nesting sites. As individuals we can also take steps to minimise our impact, by following ethical guidelines set out by Birdlife Australia - see excerpt below. "... ‘nesting birds’ is defined as the period from the start of nest building, through egg-laying, incubation and rearing of the chicks until the last young bird in a nest has fledged. A fledgling (whether it be an atricial or precocial chick – these terms are described elsewhere) is described as any young bird that has left the nest permanently.Photographers MUST keep an appropriate distance from nesting birds. Nesting is the most critical and stressful time in a bird's life. It is vitally important that photographers keep an appropriate distance from nesting birds so as to ensure that they do not: - accidentally, or deliberately, cause damage to the nest or nest site; - cause nest desertion or stress to the nesting adults or nestlings; - attract predators to the nest site; and/or - remain at a distance from the nest site, which elicits a behavioural response from the nesting bird(s) - such as ‘broken wing’ response or the nesting bird not returning immediately to the nest." Further reading
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AuthorMy name is Garry and I am extremely passionate about the environment. I have completed my BSc. Conservation and Wildlife Biology with First Class Honours and have worked in the Environment sector since 2009. Archives
September 2019
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Photos used under Creative Commons from sean.kelleher1, BioDivLibrary, BioDivLibrary