[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Elanus scriptus | [authority] Gould, 1842 | [UK] Letter-winged Kite | [FR] Elanion lettre | [DE] Schwarzachsel-Aar | [ES] Elanio Escrito | [NL] Letterwouw
Members of the genus Elanus are rather small kites. Their wings are long and pointed, the tail double rounded. They have small bills and feet, and are generally grey and white with varying amounts of black on the shoulders. The genus is cosmopolitan, but favours tropical or sub-tropical climes. Only in Australia do two species of this genus co-exist, both of which are unique to that continent, although one – the Australian Black-shouldered Kite (Elanus notatus) is closely related to, and may be a race of the Black-shouldered Kite (Elanus Caeruleus).
Small, pale kite, similar to Black-shouldered Kite Elanus caeruleus. Black spot in front of eye. Underparts white. Upperwing coverts and alula coverts black. Primaries dark grey. Tail white with central feathers tinged grey. Rest of upperparts pale grey. Underwing white to greyish white with black bar from axillaries to base of primaries. Iris red; bill black; cere horn-coloured; legs pink or whitish. A Small, mainly white, hawk unlike most Australian hawks, but difficult to distinguish from the Australian Black-shouldered Kite at rest, although it is larger, and paler grey. In flight it is distinguished at once by the under-wing pattern. The black shoulder patch is larger in fully adult individuals. The young of this species are plain brown, not streaky brown on the head, and have the black under-wing pattern well developed early. They can thus be distinguished as soon as they can fly.
Australasia : Australia. Elanus scriptus occurs in the eastern arid zone of Australia but occasionally irrupts to all parts of the continent. The species is usually confined to the Coopers Creek drainage system, whilst its wider distribution is thought to be centred on the Barkly Tablelands in the eastern Northern Territory and river systems in south-western Queensland, north-eastern South Australia and north-western New South Wales
This is a largely nocturnal species, hunting at night, and tending to rest in coolabah trees Eucalyptus coolabah during the day. It inhabits open or sparsely wooded country, usually in flocks, but also seen as pairs and singles. This is an inhabitant of the drier interior parts of Australia, generally less numerous in areas where it occurs together with the Australian Black-shouldered Kite. It is also much more gregarious than that species at all times, and is nomadic, suddenly appearing for a relatively short period in large numbers into new areas following upon good food years. They may breed during these irruptions, or disappear without breeding. It is possible that these movements are connected with mouse plagues, at least in that these may allow large-scale successful breeding in the normal range. They are also quite irregular.
The Letter-winged Kite is a colonial nester, breeding in groups of twelve to eighteen pairs, and possibly more, in clumps of trees near waterholes. Colonies have been three to five miles apart in suitable country, in the progress of a mouse plague, which may represent exceptionally favourable conditions. The same colony site is used for a series of years. The nests are built in trees, 12-35 feet from the ground, and are used for more than one year. New ones are small, eleven to fourteen inches across, by eight inches deep, with a cup eight inches across by three inches deep in the centre, lined with green leaves and much felted fur. Older nests may be 26 inches across by ten inches or more deep. They are made of twigs, collected from the ground nearby, and carried in the feet as a rule. Both sexes build. Occasionally they use the foundation of an old nest of another species, but normally construct the nest themselves; old nests become heavily fouled with droppings and debris.
Three to six eggs are laid, usually four to five, at least in favourable mouse years. The laying season in a colony is extended, from May to early July. The normal breeding season is said to be from August to November, but possibly varies according to food supply. Only the female incubates, and she is fed on or near the nest by the male. Sometimes she leaves the nest and flies to meet him when he brings food, with fluttering wings, and calling. The incubation period is more than 21 days.
Three weeks after the young hatch they are mottled with feathers on the back; at four weeks they can just fly and may leave the nest if disturbed. The length of the fledging period is probably about 35 days. The male brings most of the prey in the fledging period. On arrival with food he calls, the female answers with a lower-pitched call, leaving the nest to receive the food, which she then takes to the nest and gives to the young. Later, both sexes take part in hunting for the brood.
It flaps heavily near the ground, but can also soar very gracefully, and when hunting it regularly hovers, like others of the genus. It tends to be crepuscular, roosting during the day at breeding colonies, and hunting in the dusk and by moonlight; these habits are perhaps connected with its food supply of mice, and vary according to circumstances. Diet consists of small mammals, especially mice of various sorts; small reptiles and large insects. All prey except some of the insects is taken on the ground.
copyright: T. Tarrant
This species qualifies as Near Threatened because the population size becomes moderately small during the periods between explosions in the rat population. There appears to be inadequate knowledge on key sites and habitat use by the core population, which may be sensitive to other threats when rat numbers are low.
Population cycles appear to be linked to those of the principal prey, the plague rat Rattus villossimus, which has population explosions following high rainfall. In years when rats are numerous the species can breed rapidly and be abundant. When rat populations crash following the onset of drought, birds are forced into areas that are outside their normal range and eventually most perish. These explosions in population and range rarely last for more than a year, after which the species’s distribution again contracts. Little is known about the intervening lean times when the species is rarely seen and the population may fall near to 1,000 individuals. Despite such fluctuations the species is regarded as secure. There are no known major threats, although intensification of cattle grazing may eventually affect rat numbers and hence the species’s populations. Cats are known to predate nests, and may take significant numbers of nestlings, but this is yet to be confirmed by careful study.
Dispersive and irruptive. Breeding birds concentrate around rat plagues, slowly moving with advancing plague front. When plague collapses, many birds (mostly immatures) disperse randomly towards coast where they die of starvation. Subsequent repopulation of arid zone by nucleus of surviving adults that stay put.