The Australasian Ornithological Conference 2019 wrapped up in Darwin on Friday July 5 and was a great success. The second day of the conference featured a raptor symposium, with presentations on a variety of diurnal and nocturnal raptor spanning the breadth of our continent.
A Powerful Bird for Conservation by Beth Mott
Beth Mott talked about the citizen science Powerful Owl Project. The project began in Sydney in 2011, and has since expanded to Brisbane in 2018, with incidental sighting in Melbourne also included in the program. This project provides a conduit for the public to engage in direct conservation action for a threatened species that has increasingly been observed in capital cities.
The Powerful Owl project implements a national approach to understand the urban ecology of our biggest threatened owl species, the Powerful Owl (Ninox strenua). Citizen scientists work for the Powerful Owl project by collecting data on breeding success, habitat use and diet. By examining diet data within the urban landscape, a shift in diet towards ground-dwelling fauna has been identified, highlighting an emerging risk of poisoning. The Powerful Owl Project illustrates that well managed and effective data collection from citizen scientists can further our understanding of threatened Australian wildlife, whilst directly assisting land managers in threat mitigation.
Spatial Ecology of the Red Goshawk by Chris MacColl
Chris MacColl has started a PhD project that aims to improve knowledge of the Red Goshawk’s ecology by attaching solar-powered GPS transmitters onto the species. The Red Goshawk is one of Australia’s rarest birds of prey and occupies the highest trophic levels in the food chain. Their predatory habits provide ecosystem services by exerting top-down pressure onto prey populations.
The development of small GPS transmitters has enabled the safe attachment to the bird based on its relative carrying capacity (e.g. ≤3 % of total body weight). Four Red Goshawk on Cape York Peninsula have had transmitters fitted to provide a high-resolution, broad-scale data set on the species spatial ecology.
Breeding Territory Defence Behaviouy by White-bellied Sea-eagles by Judy Harrington
The EagleCAM project in Newington Nature Reserve in Sydney monitors the breeding behaviour of a pair of White-bellied Sea-eagles (Haliaeetus leucogaster). Judy Harrington described interesting defence behaviour at the subject nest.
In July 2017, following an early morning feed, a recently hatched chick was left unattended most of the day. At dusk loud calling was heard and interaction observed between eagles over and beside the nest. Two eagles, talons thrusting, fell to the ground below, apparently injured. A team of volunteers entered the forest in the dark to find two adult eagles on the ground. One eagle was captured and taken into care, where it died overnight. This was revealed as a young female, an intruder at the nest. During the following day, the resident eagles were heard calling and were seen on the nest tree, mating several times.
In the 2018 breeding season, the male defended the territory against another intruder in the area. Apparently injured, he failed to bring food to the nest for some time, thus contributing to the death of the smaller chick.
Long-term banding study of the Christmas Island Goshawk by Mark Holdsworth
Since 2004, the endangered Christmas Island Goshawk (Accipiter hiogastor natalis) population has been banded to provide basic demographic and behavioural information to inform conservation management of the species. The research program has shown that the oldest female is >13 years and the oldest male >10 years and the population appears to be stable over the study period. Individuals have been sighted across the island but the species is very tolerant of conspecifics, with no apparent territory defence.
Mark described the unique observation and capture techniques that enabled the banding of 285 individuals, and presented results of the long-term study, highlighting the knowledge gaps for future research into this fearless raptor.
Where do Eagle Dare: Post-fledging and dispersal behaviour in the Wedge-tailed Eagle by Simon Cherriman
Simon was not able to present at the conference due to the birth of his first child. Ever the innovator, Simon produced a video that was shown at the conference instead.
The Wedge-tailed Eagle (Aquila audax) is Australia’s largest raptor and one of three native, terrestrial apex predators. Gaps in knowledge remain about key aspects of its ecology, including post-fledging behaviour and juvenile dispersal. Knowledge of these life-history traits contributes significantly to an understanding of the landscape-scale habitat requirements of ‘nomadic’ juvenile eagles, and is especially important for long-term conservation of the species.
Simon’s research has used GPS/Satellite transmitters to study the post-fledging behaviour and early dispersal movements of 22 juvenile Wedge-tailed Eagles. Juveniles remained in their natal home range during the post-fledging period for an average of 155±28.7SD days (range 102–221 days), covering an average area of 24.6±15.5SD km2 (5.9–50.5 km2). All eagles made long-distance movements immediately after leaving their natal home ranges, with maximum displacement distances averaging 621±367SD km (263–1,213 km) within 2 months. This data is comparable with other studies on large Aquila species, and provides evidence that conservation management actions must be large-scale if they are to cater for birds utilising such vast areas.
Breeding biology of the Pacific Baza in subtropical coastal New South Wales by Keith Fisher
Keith Fisher documented the breeding biology and behaviour of two pairs of Pacific Bazas (Aviceda subcristata) in subtropical north-eastern New South Wales from 2007 to 2018. Breeding occurred during September to January, sometimes extending to March. The pre-laying period occupied late August and September and nest-building took 5–18 days. Incubation at two nests was 31 and >27 days, from 7 October and early November.
The post-fledging dependence period lasted at least 22 days, juveniles were independent and joined other broods in the area at 29 days, and they left the study area 45 days after fledging. Delivered prey was predominantly insects, especially cicadas and phasmatids by number, and tree-frogs Litoria sp. by biomass.
Keith described various behaviours, including vocalisations, inter- and intraspecific interactions. Changes in juvenile morphology through the post-fledging period were also described.
Movement ecology of a top-order predator – Powerful Owl’s response to urbanisation by Nick Bradsworth
Nick Bradsworth presented on the ecology of the Powerful Owl (Ninox strenua) in urban environments. His research involved analysis of how Powerful Owl’s use space and habitats in urban environments of Melbourne.
Urban Powerful Owls were caught and attached with GPS tracking devices to investigate their fine-scale movement ecology. Data obtained from GPS tracking helped determine the size of home ranges, travel distances, time spent in particular areas of the landscape whilst foraging and environmental factors influencing movements. This knowledge enables the development of habitat management strategies to ensure the ongoing survival of the species in urban environments.
Impacts of fishing to coastal raptors in Queensland by Vicky Thomson
Vicky’s presentation focused on the impacts of fishing to Australia’s coastal raptors, specifically Eastern Osprey (Pandion cristatus), White-bellied Sea-eagle (Haliaeetus leucogaster), Brahminy Kite (Haliastur indus) and Whistling Kite (Haliastur sphenurus).
Currumbin Wildlife Hospital on the Gold Coastin Queensland is the only raptor rehabilitation facility in the region. To determine the physical impacts of urbanisation on coastal raptors on Australia’s mid-east coast, Currumbin Wildlife Hospital admissions data was assessed from May 2010 to January 2018. Birds were admitted to the hospital as a result of anthropogenic injuries more often than other causes, with such injuries resulting in a greater chance of euthanasia or death. The most significant impact was fishing equipment entanglement. This impact was most significant for Brahminy Ktes and Eastern Ospreys. Fishing is a popular recreational activity on the east coast of Australia and as such it is important to continue education and provide tackle-bins in popular fishing areas to reduce the number of coastal raptors impacted.
Breeding Habitat and productivity of the Little Eagle near Armidale, NSW by Candice Larkin
Candice described the nest-site characteristics of the threatened Little Eagle (Hieraaetus morphnoides) near Armidale, on the Northern Tablelands of NSW. This project involved the analysis of Little Eagle nest trees and surrounding woodland within 25m of the nest, and landscape vegetation within 200 m and 2 km radii of the nest using GIS technology.
Little Eagles typically nested ≥14 m above ground in a fork or mistletoe in the canopy of emergent living eucalypts in sheltered positions, in woodland patches (>5 ha); <200 m from the woodland edge, ≥11 m from an agricultural edge; ≥38 m from the nearest rural dwelling; >1 km from suburbia; and farther from sealed roads than gravel roads and minor tracks.
Breeding productivity in 2017 and 2018 combined (n = 15 and 18 territories, respectively) was 0.91 young fledged per attempt (clutch laid) and 0.67 young fledged per occupied territory per year. Nest sites were used annually for at least 3–7 years. Nest abandonments or site shifts were associated with human disturbance (e.g. clearing and construction in or beside the nest patch); death of the nest tree or nest stand (‘eucalypt dieback’); pindone baiting for rabbits; and displacement by Wedge-tailed Eagles and ravens.
Due to most Little Eagle nests occurring on private land the following recommendations were made: greater protection of breeding habitat, nest sites and foraging habitat; woodland regeneration (especially riparian); and establishment of buffers around active nests of ≥1 km from landscape-changing developments such as urbanisation.
Rodenticide Exposure in Australian Raptors: Past Literature, Present Studies, and Future Directions by Mike Lohr
Mike was selected to present as recipient of the Stuart Leslie Bird Research award for his research on secondary poisoning of Australian raptors involving anticoagulant rodenticides (ARs).
Mike’s research has indicated widespread exposure to ARs in Australian raptor species using urban and peri-urban habitats. Sampling in Southern Boobooks in Western Australia has demonstrated prevalence and severity of AR exposure among the highest recorded instances in the world literature for a predatory bird.
Future research priorities to address the issue include identifying novel vectors or ARs and mechanisms driving exposure in Australian raptors and determining exposure rates and relative risk profiles in raptor species of conservation concern. Recommended policy actions to mitigate the threat to raptor populations include the listing of stronger second generation ARs as a threatening process under the Environment Protection and Biodiversity Conservation Act and stricter legislation regarding the sale of ARs within Australia. Without urgent action there remains a risk of further declines in a number of threatened raptor species and unforeseen ecological consequences of widespread poisoning across an entire trophic level of organisms.