Family ACCIPITRIDAE Vigors, 1824

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Introduction

The Accipitridae, a group of diurnal birds of prey, is one of the larger avian families containing 258 species within 66 genera, 22 reputedly have occurred in Australia. Recently there has been a tendency to split the family in two as Accipitridae and Pandionidae. Included within the family (sensu lata) are hawks, eagles, kites, harriers, Old World vultures and ospreys. This is one of the most diverse non-passerine bird families and greatly variant in size, shape and behaviour traits. Accipitrids have been variously divided into several subfamilies — six occur in Australia.

Apart from the Antarctic region and numerous oceanic island groups the family has a cosmopolitan distribution. Although of a diurnal nature several extend this to include crepuscular hunting activities (e.g. Elanus scriptus). Most are solitary and territorial although there is a tendency to follow prey movements. Size variation in the family extends from small (e.g. Accipiter spp.) to large (e.g. Aquila spp.) with the male of a species exhibiting sexual dimorphism, being proportionately smaller than the female. Although adults of both sexes have a similar plumage colour and pattern, the juveniles of several species have distinctive markings. Sexual dimorphism tends to be more apparent within species that rely on a principally avian diet.

The majority of species have broad, round wings that have fingered tips and these species soar and glide. Others have long, narrow and pointed wings and hover, much like the smaller falconids. A large number are counter-shaded and are generally coloured using a combination of grey, buff and brown. Several species have crests or subcrests while many uncrested species, if alarmed, have an ability to raise and lower their crown feathers. Old World vultures have unadorned, unfeathered, heads. All have a dense under-down on their feather shafts. Their strongly decurved bill has a yellow cere at the base of the maxilla, covering the nostrils. The maxilla of a few species has a notch or ‘tooth’ similar to that of the falconids.

An accipitrid's anisodactyl foot is powerful and is used, in combination with their sharp talons, to grip and kill prey. The shape and size of the tarsi is correlated with diet: those that feed principally on birds have long and thin tarsi (Accipiter); whereas those taking larger mammals are much thicker and stronger (Haliaeetus). Well-developed senses are adapted to assist hunting: acutuity of vision enables them to select prey from long distances. This sight is assisted by their large eyes having two foveae within the retina, thus providing them with binocular vision, and within the eye itself are the largest pectens of any birds. In addition they have excellent hearing that assists them in the location of hidden potential prey.

The habitat selection for the family comprises woodlands and forests, open grassland and desert. While numbers fluctuate within these habitats, following the frequency of cyclic prey availability, they are generally found in low densities. Several species will form flocks when prey are numerous (e.g. Milvus spp. at the head of large grassfires). They hunt while on the wing, gliding or soaring to locate prey and then stooping to make the kill. All species within the family have a crop for food storage. This allows them to gorge themselves at a kill and then move away from the carcase to digest the food. Prey consists of birds, small to medium-sized mammals, reptiles, fish, frogs, snails and insects, and each group is specialised in hunting for particular species and sizes. Some are purely carrion feeders while other will also take some fruit.

Hunting by small species is achieved utilising stealth accompanied by a short but swift attack with a flycatcher like sally (Accipiter spp.). Much of the food taken by hawks and eagles is obtained on the ground and consists primarily of large to small mammals, birds, reptiles, and some carrion. Others (Elanus spp.) will hover kestrel-like before stooping to the prey. The African harrier-hawks (Polyboroides spp.) take young birds from nests and in the situation where these are within hollows they have evolved specialised double-jointed legs for extracting them.

While generally silent, all accipitrids are capable of vocalisations, particularly during breeding. These consists of screams, yelps, mews and cackles between mating pairs; vocalisations are used by some to advertise territories. Pre-breeding displays are elaborate aerial displays above or near to the nesting area; these may include diving and undulating flights and claw grasping. Adult pairings are often permanent. The majority of accipitrids construct arboreal nests or usurp nests of other species. Nests comprise sticks, and are often lined with green leaves; the larger species construct large and bulky nests which are often reused although some maintain a series of nests that are used alternatively. One genus (Circus spp.) nests on the ground, using reeds as nesting material.

Clutches of the cylindrical or short-oval egg vary from two or three in the larger species to three to five for smaller species. The adult female provides the incubation which last between 28 to 50 days, and then she cares for the nestlings. Males hunt to provide food for the young. The captured prey are presented to the female who tears it to small pieces and feeds the young. In the Circus spp. the male passes the food to the female while in flight. As the young grow, adult females will leave the nest to assist in provision of food. The young are semi-precocial and nidicolous, fledging when 28–120 days old. During this period they will acquire two moults of down. Often the youngest hatching will not survive and can be consumed by its siblings. They continue to be fed by the adults for several weeks after leaving nest.

Excluded Taxa

Vagrant Species

CAVS:8033
ACCIPITRIDAE: Accipiter gularis (Temminck & Schlegel, 1844) [Japanese Sparrowhawk]

CAVS:8032
ACCIPITRIDAE: Accipiter soloensis (Horsfield, 1821) [Chinese Sparrowhawk]

CAVS:0801
ACCIPITRIDAE: Aquila (Aquila) gurneyi G.R. Gray, 1861 [Gurney's Eagle; vagrant to Torres Strait Islands] — Christidis, L. & Boles, W.E. 1994. The Taxonomy and Species of Birds of Australia and its Territories. Monograph 2. Melbourne : Royal Australasian Ornithologists Union iv 112 pp.; Christidis, L. & Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. Melbourne : CSIRO Publishing 288 pp. [21, 118]

CAVS:0792
ACCIPITRIDAE: Pernis ptilorhynchus Temminck, 1821 [Oriental Honey-buzzard; vagrant to Mainland Australia & Christmas Island] — Christidis, L. & Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. Melbourne : CSIRO Publishing 288 pp. [21, 115, 117]

General References

Christidis, L. & Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. Melbourne : CSIRO Publishing 288 pp.

Lerner, H.R.L. & Mindell, D.P. 2005. Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37: 327-346

Mindell, D.P., Sorenson, M.D., Huddleston, C.J., Miranda, H.C. Jr, Knight, A. & Yuri, T. 1997. Phylogenetic relationships among and within select avian orders based on mitochondrial DNA. pp. 213-247 in Mindell, D.P. Avian Molecular Evolution and Systematics. San Diego, California : Academic Press pp.

Wink, M. & Sauer-Gürth, H. 2004. Phylogenetic relationships in diurnal raptors based on nucleotide sequences of mitochondrial and nuclear gene markers. pp. 483-498 in Chancellor, R.D. & Meyburg, B.-U. Raptors Worldwide. Budapest : WWGBP/MME.

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