Biology of the Little Eagle on the Northern Tablelands of New South Wales

Abstract

DEBUS, S.J. S. 1984. Biology of the Little Eagle on the Northern Tablelands of New South Wales. Emu 84: 87-92. The diet and breeding biology of the Little Eagle Hieraaetus morphnoides were investigated at Armidale, New South Wales in 1980. Data were supplemented by the RAOU Nest Record Scheme. Little Eagles took a wide range of vertebrate prey species in the breeding season. Prey items recorded at three nests consisted, by number, of about 60% mammal, 25% birdsnd 15% lizard and these figures agreed closely with the percentage occurrence of these prey types in pkllets (~5 5 % mammal, 25% bird and 20% lizard). Active nests were in living trees in patches of woodland. The ratio of two-to single-egg clutches was about 2:l. The incubation period was 36 to 40 days, and males shared incubation. The nestling period was about nine weeks, and the post-fledging dependence period appeared to last at least six weeks. The breeding cycle occupied about four months from nest building to fledging, and, for the district, about five months (August-January). Fledging success was about 0.5 young per pair per year, and about one in six successful nests raised two young. Breeding density was at least one pair per 1600 ha. Prey taken from each home range in the six-month breeding season was estimated at 120 young lagomorphs (48 kg), 50 birds (3 kg) and 30 lizards (4 kg).

Alarm Calls of the Australian Magpie (Gymnorhina tibicen): Predators Elicit Complex Vocal Responses and Mobbing Behaviour

“…At the time of the experiments, two breeding pairs of little eagle were known to live in the Armidale vicinity. This might suggest that the magpies in the semi-rural localities perceived the little eagle as somewhat more threatening than the wedge-tailed eagle (both in numbers and in likelihood of attack) and this is also consistent with the greater proportion of birds in the diet of the little eagle than in that of the wedge-tailed eagle [28].…”

“…The majority of the little eagle's diet consists of mammals, mainly rabbits [27] but, when rabbits are not available, the majority (77%) of its diet consists of birds. Of the birds in its diet, 6% are magpies at times outside the magpie's breeding season, rising to 18% when magpie fledglings are available [28]. Birds are also a part of the diet (about 14-16%) of varanid lizards [29,30], obtained by foraging on the ground as well as by climbing trees to prey on eggs and nestlings, but the contribution of magpies to this is unknown.…”

Predation by Australian magpies (Gymnorhina tibicen) on pasture invertebrates: Are non‐territorial birds less successful?

“…1972). In Australia, magpies risk predation by little eagles (Debus 1984), wedge-tailed eagles (Brooker & Ridpath 1980), introduced foxes and feral cats, and the eggs and nestlings are taken by the Australian raven (Carrick 1972) but mortality due to predation has never been quantified. However, the low adult mortality of territorial magpies dispersed at the same densities as flock birds in both the Australian and New Zealand populations (Carrick 1972;Veltman 1989) and the fact that some of their predators are introduced species, casts doubt on predator avoidance as the primary selective agent in the evolution of the flocking lifestyle.…”

Clever strategists: Australian Magpies vary mobbing strategies, not intensity, relative to different species of predator

“…Based on this assessment, we predicted that the Little Eagle ( Hieraetus morphnoides ) would represent the greatest threat since up to 77% of its diet may consist of birds (Debus, 1984). The Brown Goshawk ( Accipter fasciatus ) would be next since this species is also an avid bird hunter and birds constitute 37–66% of its total diet (Marchant & Higgins, 1993).…”

“…Monitor Lizards seek out prey primarily by scent and, by climbing trees (King & Green, 1999), whereas snakes are primarily ambush predators and, like the lizard, may climb trees or attack on the ground. Wedge-tailed Eagles, the largest of the Australian raptors, use glide attacks, direct-flying attacks, or tail-chasing with the majority of prey being captured on the ground (Marchant & Higgins, 1993), whereas Little Eagles, which are substantially smaller than the Wedge-tailed Eagle and very agile, attack in flight from high altitudes or from perches (Debus, 1984). By contrast, the Brown Goshawk is mainly an ambush hunter and it flushes out prey, the majority of its attacks relying on stealth and surprise (Marchant & Higgins, 1993).…”