Australian Bush Birds
Spotted Harrier  -  Circus assimilis
Spotted Harrier
Spotted Harrier at Bladensburg Nat Pk, Queensland.
Spotted Harrier
Spotted Harrier in flight at Bladensburg Nat Pk, Queensland. The barring on the tail is visible as well as the conspicuous, widely fingered black wingtips.
photograph The chestnut spotted white underside is clearly seen in flight and so is the white area under the outer wing. The yellow legs are tucked up against the tail (Bladenburg NP, Qld)
Spotted Harrier - page 2
map map The Spotted Harrier - Circus assimilis - (50-61 centimetres long with wingspan of 121 to 147 centimetres) is a large raptor with long and broad wings. Male and female are similar; average weight of males is 465 grams, average weight of females is 671 grams. Upper parts are blue-grey, head is grey with red-brown face; eye is prominent yellow, bill is black. Underside is red-brown (also known as chestnut) with white spots. Tail is barred dusky and grey-white. Wings are grey speckled white on the upper side with chestnut shoulder and conspicuous, widely fingered, black wingtips. Wing underside is mainly chestnut on the inner wing with a widening white rear barred band; the rear edge is dark grey. Legs are long and yellow; claws are black. The tail is long, barred and rounded in flight.

Immature birds have grey-brown upper parts with buff-brown tips, rump is pale; under parts are russet streaked dusky. Tail is grey with dull dusky bars.

The overall appearance of the adult bird is of grey upper parts with chestnut underside spotted white; black wing tips may be conspicuous.

The Spotted Harrier is found all over Australia (rarely in Tasmania) but avoids heavily forested areas and is found predominantly in cropland, grassland, low shrubland and open woodland of inland and northern Australia; sometimes over open coastal grassland, heath or swamps in the south.

This is a solitary hunter, flying a methodical search over vegetation for prey; gliding low over grassland with wings upswept and tail fanned. At other times soaring high and circling, sometimes lowering the legs in flight for additional control. Wings occasionally flap while gliding. Occasionally hovers briefly with slow wing beats just above the vegetation with talons extended ready to snatch a ground bird, small mammal or reptile. Prey is seized by diving to the ground or after a short chase if the prey is flushed. Prey is always captured on the ground. Prey comprises ground birds (quails, larks, pipits), mammals (young rabbits, rodents), reptiles, large insects and rarely carrion.

The Spotted Harrier perches on the ground or in trees and roosts on the ground, occasionally sheltering in the shade of trees.

The Spotted Harrier is unique among harriers in that it nests in trees. Temporary pairs form after display flying involving flying to height, then descending in slow spirals and side slips, occasionally plumetting with half-closed wings. The pair work together to build a new nest every year; the nest is a flat and bulky platform made of sticks lined with green leaves in a low tree 2 to 15 metres above the ground in a solitary location. Fresh green leaves are added while the nest remains in use.

Laying season in Southern Australia is September to October and June to September in the north. Two to four (usually three) eggs are laid; white or blue-tinged, rounded-oval in shape, about 48 by 40 millimetres. The male hunts then delivers prey to the incubating female in an aerial transfer. Incubation takes 33 days and young are nestlings for another 36 to 43 days as nestling, then there is a further period of at least six weeks of dependence by the fledged young. Then the younger birds disperse from the nesting site and migrate, possibly up to 1600 kilometres.

Most of a clutch of young is often reared but a pecking order develops among chicks and a dominant one may starve others or peck them to death and eat them if food is short.

The Spotted Harrier is nomadic, movements are linked to the abundance of prey species. It is widespread but generally uncommon