Wedge-tailed Eagles Aquila Audax Research Articles

Pleistocene raptors from cave deposits of South Australia, with a description of a new species of Dynatoaetus (Accipitridae: Aves): morphology, systematics and palaeoecological implications

The Pleistocene fossil record of Australian raptors (Accipitridae: eagles, hawks and Old World vultures) is very poorly understood with only three distinct extinct species confirmed until now. The small Necrastur alacer remains unstudied; however recent research has established Cryptogyps lacertosus as a valid species that, along with the very large Dynatoaetus gaffae, has potential affinities with the Aegypiinae–Circaetinae clade. These, along with a single large living inland raptor, the Wedge-tailed Eagle Aquila audax, suggest that Australia had an impoverished diversity of large raptors compared to other similar continental regions. However, fossil material similar in size to A. audax from multiple Pleistocene cave deposits raises the possibility of further taxa and is here assessed. A partial skeleton from Green Waterhole/Fossil Cave in the Tantanoola District of South Australia is referred to Cryptogyps lacertosus on the basis of similar size to bones of this species and that the associated coracoid is identical to that found with a tarsometatarsus that was previously referred to this species, coming from Leaena’s Breath Cave on the Nullarbor Plain, Western Australia. This partial skeleton allowed additional material from the Old Collections, Wellington Caves, and Walli Caves in New South Wales to be referred to this species. A second species, more robust than A. audax, is identified from material from Victoria Fossil Cave at Naracoorte. Phylogenetic analyses determined this species to be the sister taxon of the much larger Dynatoaetus gaffae recently described from several Australian sites, and so we name it as Dynatoaetus pachyosteus sp. nov. Further fragmentary remains attributable to either A. audax, C. lacertosus or D. pachyosteus are recorded from sites in the Wellington Caves complex, NSW. This study increases the known diversity of raptors in Pleistocene Australia, consistent with the presence of the more diverse megafaunal prey that existed at the time. Ellen K. Mather [ math0083@flinders.edu.au ], College of Science and Engineering, Flinders University, GPO 2100, Adelaide, SA 5001, Australia; Michael S. Y. Lee [ Mike.Lee@samuseum.sa.gov.au ], Earth Sciences Section, South Australian Museum, North Terrace, Adelaide 5000, Australia (College of Science and Engineering, Flinders University, GPO 2100, Adelaide, SA 5001, Australia); Diana A. Fusco [ diana.fusco@flinders.edu.au ], College of Science and Engineering, Flinders University, GPO 2100, Adelaide, SA 5001, Australia; John Hellstrom [ j.hellstrom@unimelb.edu.au ], Faculty of Science, School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Grattan Street, Parkville, Melbourne, 3010, Australia; Trevor H. Worthy [ trevor.worthy@flinders.edu.au ], College of Science and Engineering, Flinders University, GPO 2100, Adelaide, SA 5001, Australia.

The breeding biology of the Western Red-tailed Cockatoo Calyptorhynchus escondidus in the wheatbelt of Western Australia

ABSTRACT A breeding population of Western Red-tailed Cockatoos Calyptorhynchus escondidus was studied between July 1974 and December 1981 at Nereeno Hill, in the northern wheatbelt of Western Australia. Egg-laying occurred during two clearly defined periods each year; with peaks mid-March to mid-April (Autumn breeding) and early-August to mid-October (Spring breeding). Thirty-two percent of the 459 eggs laid during the study were laid in Autumn and 68% in Spring. Growth rates of nestling wings and body mass were similar between seasons and years. Nearly one third of breeding attempts failed during incubation and 40.7% successfully fledged a nestling. Fledgling survival in the first year was low (17.5%), however, annual survival was higher after the first year; 80.0% after four years. Birds were killed by Wedge-tailed Eagles Aquila audax, shot by farmers, and drowned in stock troughs. Based on evidence from one individually-marked pair, Western Red-tailed Cockatoos may form long lasting pair bonds. While females breed every 12 months, some have bred in both Autumn and Spring seasons. Young Red-tailed Cockatoos remain with their parents up to two years after fledging, and adults may have young from two breeding seasons accompanying them. The breeding biology of Red-tailed Cockatoos is compared with that of closely related species from the genera Calyptorhynchus and Zanda. Threats to the species are loss of mature hollow-bearing trees and almost complete dependence on the seeds of Double Gee Emex australis, an introduced agricultural weed, for food.

A giant raptor (Aves: Accipitridae) from the Pleistocene of southern Australia

The giant accipitrid Dynatoaetus gaffae gen. et sp. nov. is described from existing and newly collected material. Initial fossil remains were collected from Mairs Cave (Flinders Ranges, South Australia) in 1956 and 1969, and comprised a sternum, distal humerus and two ungual phalanges. A further 28 bones from this individual—including the neurocranium, vertebrae, furculum, and additional wing and leg bones, most of which were incomplete—were discovered at the site in 2021. This allowed identification of additional fossils from the same species in collections from Cooper Creek (Lake Eyre Basin, SA), Victoria Fossil Cave (Naracoorte, SA) and Wellington Caves (Wellington, NSW). Dynatoaetus has variable similarity across elements to those of living species in the Perninae, Gypaetinae, Circaetinae and Aegypiinae. Parsimony and Bayesian phylogenetic analyses of combined morphological and DNA data resolved it as the immediate sister-group to the Aegypiinae within the Circaetinae + Aegypiinae clade. The robust and eagle-like morphology of the lower hindlimbs suggest that the species was a predator, rather than a scavenger, and thus functionally similar to large circaetines such as the Philippine Eagle Pithecophaga jefferyi. Furthermore, this new species is the largest known bird of prey from Australia, much larger than the modern Wedge-Tailed Eagle Aquila audax. It is outsized in Australasia only by female Hieraaetus moorei (the extinct Haast’s Eagle from New Zealand). It is inferred to have been Australia’s top terrestrial avian predator during the Pleistocene, ranging from arid inland Australia to the more temperate coast, and likely became extinct around the time of the megafaunal mass extinction which peaked around 50 Ka. Its extinction in the late Pleistocene, along with the recently described scavenging vulture Cryptogyps lacertosus, marked a distinct decline in the diversity and function of Australia’s raptor guild.

Wedge-tailed Eagles Aquila audax regularly sunning during a camera-monitoring survey

Two Wedge-tailed Eagles Aquila audax sunning were observed on images from a monitoring camera that was located at Flinders–Goolman Conservation Estate, in Ipswich Local Government Area, south-eastern Queensland. I observed the Eagles across multiple days in March–April 2023 whilst the camera was in place, despite the camera being unbaited, and originally positioned to detect Brush-tailed Rock-wallabies Petrogale penicillata. The images showed one adult, a pair of adults or an adult and a juvenile Eagle. This behaviour has been poorly documented in this species, although it has been widely observed in other bird species.

An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia

ABSTRACT The Australian pre-Pleistocene fossil record of Accipitridae (eagles, hawks, old-world vultures) comprises one latest Oligocene or early Miocene and one middle Miocene species, each represented by partial bones. Globally, most fossil accipitrids are based on single bones. The recent discovery of an older and considerably more complete accipitrid from late Oligocene sediments in Australia is therefore significant. It is derived from the Pinpa Local Fauna from the Namba Formation at Lake Pinpa, South Australia (~26–24 Ma). The fossil, described as Archaehierax sylvestris gen. et sp. nov., represents a raptor that was larger than the black-breasted buzzard Hamirostra melanosternon but smaller and more gracile than the wedge-tailed eagle Aquila audax. Comprehensive morphological and molecular phylogenetic analyses resolved Archaehierax as a basal accipitrid, not closely related to any living subfamily and perhaps the sister taxon to all other accipitrids exclusive of elanines. Relatively short wings similar to species of Spizaetus and Spilornis suggest it was adapted for flight within enclosed forests. Additional accipitrid fossils from the Namba Formation, a distal femur and a distal humerus, are incomparable with the holotype of A. sylvestris; they may represent distinct species or smaller individuals of the new taxon. lsid:zoobank.org:pub:6A25C569-3E9F-43B8-AAF8-F36CE405C06E

Breeding diets of the Little Eagle Hieraaetus morphnoides and Wedge-tailed Eagle Aquila audax in the Australian Capital Territory in 2011–2019

The diets of the Little Eagle Hieraaetus morphnoides and Wedge-tailed Eagle Aquila audax breeding sympatrically in the Australian Capital Territory during 2011–2019 were compared by analysis of pellets and prey remains (six Little Eagle territories and 13 Wedge-tailed Eagle territories; 69 and 49 collections for a total of 232 and 256 prey items, respectively). Little Eagles took 33% mammals (29% European Rabbits Oryctolagus cuniculus), 44% birds, 6% reptiles and 17% insects by number, and 65% mammals (62% Rabbits), 27% birds, 8% reptiles and <1% insects by biomass. Wedge-tailed Eagles took 59% mammals (23% Rabbits and 19% macropods), 38% birds, 1% reptiles, <1% fish and 1% insects by number, and 89% mammals (20% Rabbits, 38% macropods), 10% birds, and <1% reptiles, fish and insects by biomass. Indices of dietary diversity (Shannon Index and Standardised Food Niche Breadth) were 2.57 vs 3.07 and 0.19 vs 0.24, respectively; Geometric Mean Prey Weights (GMPW) were 164 vs 1392 g, but discounting a biased sample of insects in many pellets from two fledglings, Little Eagle GMPW was more like 340 g. Dietary proportions and some metrics for both species appear to have changed little since the preceding decade, although Wedge-tailed Eagle dietary diversity increased slightly and dietary overlap (80%) increased greatly, concomitantly with some pairs of Wedge-tailed Eagles replacing pairs of Little Eagles. Intraguild predation occurred, including Wedge-tailed Eagle predation on Little Eagles.

Scavenging birds at risk of ingesting fragments of lead bullets from kangaroo and deer carcasses in south-eastern Australia

Exposure of scavenging wildlife to lead from ammunition is a worldwide problem for wildlife management, but there has been little research on this topic in Australia. To examine which species of scavenging birds are potentially at risk of harmful exposure to lead, we deployed camera-traps to observe avian scavenger behaviour on carcasses of non-native and native mammals shot with lead-based bullets in two different locations in Victoria. We monitored 30 Sambar Deer Rusa unicolor carcasses in temperate eastern Victoria and 48 kangaroo Macropus spp. carcasses in semi-arid north-western Victoria. At least eight avian taxa scavenged from carcasses, including Wedge-tailed Eagles Aquila audax , Little Eagles Hieraaetus morphnoides , Brown Goshawks Accipiter fasciatus , Whistling Kites Haliastur sphenurus , ravens/crows Corvus spp., and three species belonging to the family Artamidae. Fifty-six percent of all carcasses were visited by birds. Corvids visited the most carcasses and typically arrived first, whereas Wedge-tailed Eagles arrived second but individually spent more time feeding. Our results indicate that a diverse avian scavenger community consumes carcasses of shot mammals in Australia, and consequently could be exposed to lead from bullet fragments.

Additions to prey taken by Wedge-tailed Eagles Aquila audax after release of Rabbit Oryctolagus cuniculus haemorrhagic disease (Rabbit Calicivirus) in 1996

Identifications of five species of birds considered prey of Wedge-tailed Eagles Aquila audax following the 1996 release of Rabbit Oryctolagus cuniculus haemorrhagic disease (Rabbit Calicivirus) in western New South Wales are given. The following taxa were identified from their sterna in Wedge-tailed Eagle nests: Sulphur-crested Cockatoo Cacatua galerita , Galah Eolophus roseicapilla , Australian Magpie Gymnorhina tibicen , Little Crow Corvus bennetti and Plains-wanderer Pedionomus torquatus .

IInteractions between Australian Ravens and raptors in a pastoral area of New South Wales: Interspecific aggression and nest-site spacing

This study, near Tamworth, New South Wales, investigated the interactions within a diurnal raptor and Australian Raven Corvus coronoides community. The Australian Raven (hereafter ‘Raven’) is an abundant breeding resident here, is the only corvid that breeds in the area, and is known to have a close association with many raptor species. It is known to interfere with nests, provide frequent harassment and decrease the breeding productivity of several nesting raptor species, yet few studies have been completed on this issue, and its significance remains unknown. The abundance of raptors and Ravens and diversity of raptor species were determined from weekly surveys along a fixed 60-km transect in autumn to late spring 2016. A negative association was found between raptor species diversity and Raven abundance. The density and distribution of active or potential raptor and Raven nests were also recorded along the transect: active raptor nests had significantly more active stick nests of other species (raptors and Ravens) nearby (within 500 m), whereas active Raven nests had fewer such active nests within 500 m. Intruding Ravens and Wedge-tailed Eagles Aquila audax elicited significantly higher rates of defensive interactions from nesting Black Falcons Falco subniger than did other diurnal raptor species; Ravens triggered the highest rate of response. An increased understanding of the factors responsible for shaping community structure is useful for the management of threatened species. The raptor assemblage around Tamworth includes five threatened species, at least four of which are known to breed there, making competition for nest-sites here worthy of research.

Does information of predators influence general wariness?

Antipredator behavior includes several qualitatively distinct activities, but few studies have determined the degree to which these activities are independent. If behaviors are not independent, then the nature of the relationship would illustrate potential performance constraints. We studied crimson rosellas (Platycercus elegans) and first focused on acoustic predator discrimination. We measured time allocation before and after playback of one of three experimental treatments (peregrine falcons—Falco peregrinus, wedge-tailed eagles—Aquila audax, and crimson rosellas) to determine whether or not rosellas discriminated predators from non-predators, and specifically whether or not they discriminated large from small predators. We then focused on the decision to flee. We experimentally approached subjects and measured the distance at which they oriented to us (alert distance) and the distance at which they fled (flight initiation distance; FID). We found that rosellas could distinguish among predators; however, there was no effect on general wariness as measured by FID. These two processes of antipredator behavior may, thus, be independent.

Wedge-tailed Eagle Aquila audax Predation on Endangered Mammals and Rabbits at Shark Bay, Western Australia

SummaryThe diet of Wedge-tailed Eagles Aquila audax was assessed from a single nest on Bernier Island and two nests on Heirisson Prong at Shark Bay, Western Australia. The nests and their immediate surrounds were searched for mammalian skulls and the numbers of each species recorded. The nest at Bernier Island was examined annually between July 1992 and October 1995 and the two nests on Heirisson Prong in October 1995. Banded Hare-wallabies were the most abundant prey item found in the Bernier Island nest over the four year period comprising 53.0% of all skulls, followed by Rufous Hare-wallabies at 35.9%, Burrowing Bettongs at 8.5% and fish at 2.6%. On Heirisson Prong, one bettong skull and 91 rabbit skulls were collected. Wedge-tailed Eagles displayed a preference for larger prey items on both Bernier Island and Heirisson Prong. They are diurnal predators but on Bernier Island their prey species are largely nocturnal. Possible hunting techniques are discussed.

Geographic Variation in Egg Size, Clutch Size and Date of Laying of Australian Raptors (Falconiformes and Strigiformes)

SummaryApproximately 5000 clutches of eggs, and associated data, in oological collections and the field, were used to describe date of laying, egg size and clutch size of all 24 diurnal raptors, and eight owls occurring in Australia. Within families, smaller species tended to have larger clutches and to lay later than larger species. Several patterns in geographic variation were detected. For several species, date of laying occurred about 2–3 days later for every degree of latitude southwards. Weak clinal variation in clutch size was found for ten species: clutch size of some Australasian falcons varied with latitude; that of the true eagles and three milvine kites varied with longitude. Weak clinal variation in egg size was found for ten species, seven conforming to Bergmann's latitudinal rule for body size. Sortie evidence was found for: the existence of a contested subspecies, the small northern subspecies of Brown Goshawk Accipiter fasciatili didimus, north of 23°; the subspecific separation of the Osprey into the northern race Pandion haliaetus melvil- lensis, and southern race P. h. cristatus with larger, broader eggs; the subspecific separation of the large Tasmanian Wedge-tailed Eagle Aquila audax fleayii from the mainland population; and the recognition of a small, western race of the Brown Falcon Falco berigora occidentalis.

Effect of Drought on a Breeding Population of Wedge-tailed Eagles Aquila audax

SummaryRobertson, G.G. (1987). Effect of drought on a breeding population of Wedge-tailed Eagles. Emu 87, 220–223.The number of pairs of Wedge-tailed Eagles Aquila audax breeding and their breeding success were assessed over a range of seasonal conditions from 1980 to 1985 near Menindee, in western New South Wales. The number of eagles breeding varied from 10–12 pairs during favourable years to three pairs during drought. Overall, the number of eagles breeding was not significantly correlated with both the density of Rabbits Oryctolagus cuniculus and the pasture biomass two months before laying, at hatching and at fledgling, and with the rainfall over the six months preceding these events. Few pairs bred when Rabbits were scarce but when Rabbits were abundant the number of eagles breeding did not exceed 12 pairs. Presumably the response by eagles to high densities of Rabbits was limited by the territoriality of the eagles. Breeding success averaged 0.99 chicks per pair and remained high during drought.

The Diet of the Wedge-Tailed Eagle, Aquila Audax, in Western Australia.

The diet during nesting of the wedge-tailed eagle Aquila audax was examined in several regions of Western Australia. On the arid Nullarbor Plain, rabbits were by far the major food item despite the presence of a number of other prey species. In the south-west of the State, which has a Mediterranean climate, birds (especially ducks, parrots and corvids), rabbits and sheep were the most important foods in a very diverse diet. On the arid western coast near Carnarvon, kangaroos and sheep predominated as food but a number of foxes and cats were also taken. In northern Western Australia, macropods appeared to be the main food source. Eagles were capable of capturing a large number of different species of reptiles, birds and mammals, and these varied considerably in size. Snakes, and birds from orders Pelecaniformes, Ardeiformes and Charadriiformes were rarely taken. Lambs made a significant contribution to the diet of eagles in some regions of Western Australia but the number eaten relative to the number of neonatal deaths from all causes was not high. In the regions studied, predation by eagles seemed unlikely to have a significant effect on rabbit numbers.

Field Observations of the Behaviour of the Wedge-Tailed Eagle

SUMMARYBrooker, M. G. 1974. Field observations of the behaviour of the Wedge-tailed Eagle. Emu 74: 39–42.The diurnal pattern of activity of the Wedge-tailed Eagle Aquila audax is outlined and various patterns of behaviour are described. Though aerial displays are probably used to maintain territory, there does not appear to be any elaborate courtship display on perches or in the air. This suggests that such displays arc unnecessary in a long-lived species that forms long-lasting pairs.