The Marsh Harrier, whose old English names include Swamp Hawk, Moor Buzzard, Bald Buzzard, Duck Hawk, Snipe Hawk, Marsh Hawk, Moor Hawk, Brown hawk, Bog Gled, Dun Pickle, White-headed harpy, Puttock and Kite is itself a cosmopolitan bird, existing in almost all of the Old World except in the far north. It is an ancient species, the oldest records in Britain dating back to the Iron Age - around 3,000 years ago!
Being a good bit bigger than the Hen Harrier, the Marsh Harrier can take a wider variety of prey. During the breeding season his hunting area is reduced and it must take advantage of local abundances. At that time he concentrates on marsh birds and small mammals which are easily caught, relying on surprise rather than speed. The Harrier generally quarters flat areas at a height of only a few metres, always taking advantage of cover, sometimes hovering or performing impressive aerobatics before dropping with claws outstretched. Prey is sometimes spotted from a low perch.
Birds taken include poultry, ducks, waders, coot, moorhen, water rail, gulls, young pheasants and partridges, and songbirds and their young. Mammals include voles, mice, rabbits, moles, rats and young hares. Frogs are also important.
The voice is rarely used outside the breeding season and even then the adults are remarkably quiet, except in courtship thereflight, when there is a wailing or peewit-like call. The female receives prey with a high-pitched piping, and intruders are threatened with a chattering kekekeke.
Status and behaviour in the wild
This species is a bird of swamps, marshes, flood plains or rice fields and reed beds. On migration it is much less likely to be seen in dry open grassland than other harriers and principally follows river valleys or coasts, though it must cross dry areas sometimes. ln its winter quarters it is often very common, e.g. in rice fields in South India, where it is almost as common as the very numerous resident Brahminy Kite Haliastur indus.
In its breeding areas, like other harriers, it spends a lot of the day on the wing, although probably less than many other harriers. It flies higher than other harriers, usually at ten to fifteen feet, and in a less buoyant and easy manner, though it has the harrier habit of gliding with wings held well above the level of the back. Although it appears, probably due to its larger size, to fly slower than other harriers its hunting speed has been estimated at 31-36 miles an hour, faster than most harriers.
The northern and most southern populations are migrants. Migration in Western Europe begins with young birds of the year in mid-August, followed by adults in September and October. Males migrate later than females and young, and arrive in wintering grounds later.
The rate and extent of migration varies according to the place of origin, northern birds leaving earlier, moving faster and travelling further than do birds from Southern Europe, which may remain most of the winter quite close to their breeding areas. The southern migration from Europe follows well-marked routes through Gibraltar or the Bosphorus, and rarely crosses large bodies of water; they may reach high altitudes up to 9,000 feet when crossing mountain passes on migration, but usually favour low ground.
Northward migration begins again in February and March, and both at this time and in autumn they are more gregarious than usual, roosting communally in swamps like some other harriers, with up to 300 together in some races. The northward migration frequently crosses the Mediterranean, so that evidently they can cross large bodies of water if necessary. Returning birds arrive in their breeding haunts from late March onwards, as late as early May in the northern parts of the range. They generally migrate singly or in small parties, not in large flocks, but often roost gregariously even when hunting singly. In winter quarters the same individuals may frequent the same area for weeks at a time.
During courtship the male carries out spectacular aerobatics over the nest and surrounding area. He soars in high circles, sometimes flying with exaggerated wingbeats, and occasionally calling. Sometimes the pair display together, when he dives down at her and she rolls over to present her talons.
The nest is well hidden in the dense reed bed or other thick vegetation in shallow water. The female takes about 10 days to build the pile of sticks, reeds and grass that serves as a nest. Meanwhile, the male makes a platform for resting and feeding. Both parents add material to the main nest during fledging.
The female incubates for 31-38 days per egg, usually starting with the first. The male provides for the female near the nest.
For the first week or so the chicks are brooded by the female, who feeds them beak-to-beak, but later they feed themselves in the nest, often with some ferocity, especially if the female is not very attentive. During lean times the bigger chicks may kill and eat their smaller siblings. The male brings food in the typical harrier way, dropping it for the female to catch in the air. As the young develop, the female helps with the hunting. She can rear the brood on her own if her mate is killed or deserts her. After a month or so the chicks scatter into the surrounding vegetation. They fledge at 35-40 days. The male soon leaves after that, but they usually remain with the female for a further 15-25 days.