Spotted Harrier (Circus assimilis)

Spotted Harrier

Subspecies

Genus	Species	subspecies	Region	Range
Circus	assimilis		AU	widespread

Genus

The genus Circus is a cosmopolitan genus of about ten species. They are medium-sized, slender hawks, the female being considerably larger than the male. They are characterised by long, narrow, rounded tails, small beaks and long, slender legs. The most notable characteristic is the owl-like ruff of facial feathers that cover unusually large ear openings – an adaptation not for low-light hunting, but to locate prey by their rustling and squeaking in tall grasses.

Physical charateristics

The Spotted Harrier is a medium-sized, slender bird of prey having an owl-like facial ruff that creates the appearance of a short, broad head, and long bare yellow legs. The upperparts are blue-grey with dark barring, and the wingtips are black. The face, innerwing patch, and underparts are chestnut. The long tail is boldly banded, with a wedge-shaped tip. Juveniles are mottled and streaked ginger and brown, with prominent ginger shoulders, fawn rump and banded tail.

wingspan min.:	121	cm	wingspan max.:	147	cm
size min.:	50	cm	size max.:	61	cm
incubation min.:	32	days	incubation max.:	34	days
fledging min.:	36	days	fledging max.:	43	days
broods:	1		eggs min.:	2
			eggs max.:	4

Range

Australasia : widespread. The Spotted Harrier inhabits Sulawesi and the Lesser Sunda Islands and is sparsely distributed throughout mainland Australia.

Habitat

The Spotted Harrier occurs throughout the Australian mainland, except in densly forested or wooded habitats of the coast, escarpment and ranges, and rarely in Tasmania. Occurs in grassy open woodland including acacia and mallee remnants, inland riparian woodland, grassland and shrub steppe. It is found most commonly in native grassland, but also occurs in agricultural land, foraging over open habitats including edges of inland wetlands.

Reproduction

Pairs nest solitarily. Unique among harriers in regularly nesting in trees. both in Australia and on Sulawesi. The nest is a platform of sticks lined with green leaves and placed 2-15 m above the ground in a living tree, rarely on the ground. Clutch size is usually 3 eggs (2-4), the incubation period is 33 days, and the nesting period is 36-43 days. The period of dependence after fledging lasts at least six weeks.

Feeding habits

Preys on terrestrial mammals (eg bandicoots, bettongs, and rodents), birds and reptile, occasionally insects and rarely carrion. It forages by low quartering or transect hunting, sometimes by hovering, and seizes prey by diving to the ground or by a short chase if prey is flushed

Video Spotted Harrier

httpv://www.youtube.com/watch?v=_pacmFYTiZs

Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Migration

Partly migratory in South, some birds wintering in tropics; status uncertain in Sula Is and Lesser Sundas, but probably only migrant to latter. In South, departure and locality of subsequent return determined by local rainfall: birds leave in dry conditions, return to areas with good rains and plagues of prey.

Distribution map

Spotted Harrier distribution range map

Planet of Birds