Long-winged, Long-legged, Hunters… Swamp Harriers

By Keith Hutton on July 29, 2014 in Other

Apart from Nankeen Kestrels and Black-shouldered Kites, both of which hover for sustained periods in open areas and are easily seen, birds of prey are not common in the Sydney region. There is a pretty good chance of seeing Whistling Kites, Brown Falcons and sea-eagles in suitable habitat, but others are uncommon or less obvious. Swamp Harriers are among the least known raptors that may be seen. It is doubtful whether or not there is enough suitable habitat left around Sydney for them to breed, but they do visit regularly and may be around in autumn and winter in more open and exposed sites.

Swamp Harriers are large, lightly built hawks with long tails, long slender yellow legs and long broad wings. They are usually noticed alone, sailing low over reeds, grasslands, heaths or crops, graceful and buoyant with small owl-like faces looking down, and wings raised, rocking gently from side to side. Occasionally they flap their wings a few times, or check and hover briefly, before dropping down into rank vegetation, or to perch – tall, upright and slim – on a low post.

Adult female or immature birds are seen most often and are dark brown above with barred wings and tails. Adult males are paler and become greyer with age, and juveniles of both sexes are dark chocolate brown with an inconspicuous pale rufous rump patch. Older birds have prominent white rump patches that are very obvious when they are flying low.

In the southwest Pacific and Australasia, Swamp Harriers occur widely in wetlands, tall grasslands, crops, heath lands, salt marshes, around bore drains inland, and on coasts and islands. They are breeding migrants in Tasmania and generally common nomads, migrants or residents on the Australian mainland in the east, southeast and southwest. Elsewhere they are scarce and nomadic.

Young rabbits and water birds the size of coots and teal normally make up more than half the food intake for Swamp Harriers, which are skilled and adaptable hunters. They also eat eggs and carrion, large insects, frogs, fish and reptiles. More than 80 percent of food searches are by low, slow quartering, but hunting on the ground has also been observed. The final kill normally involves hovering and dropping, a dive attack or a direct flight chase, and these strategies account for 80 – 90 percent of successful pursuits.

Swamp Harriers appear to have increased following the clearing of forests and introduction of rabbits, but then decreased after the introduction of rabbit control strategies. Shooting, trapping and poisoning affected them after they had become so successful that bounties were paid to reduce their numbers. They are now fully protected throughout Australia but remain vulnerable when nesting, as they readily desert their nests after even minor disturbance. Furthermore, when nests are in crops they are subject to destruction by farm machinery and trampling by livestock. Road kills and power line collisions also cause losses. Nevertheless, recent surveys suggest Swamp Harriers in Australia are secure despite some regional variations in numbers.