NT
Letter-winged Kite Elanus scriptus



Justification

Justification of Red List Category
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 justification
The population is almost impossible to assess due to its extreme fluctuations. 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. Little is known about the intervening lean times when the species is rarely seen and populations may fall near to 1,000 individuals. Its population size generally remains between 1,000-10,000 individuals, roughly equivalent to 670-6,700 mature individuals.

Trend justification
Population cycles appear to be linked to those of the principal prey, the plague rat Rattus villossimus, which has population explosions following high rainfall (Olsen 1995). These explosions in population and range rarely last for more than a year, after which the species's distribution again contracts (Garnett 1993). Despite such fluctuations the species is regarded as secure (Garnett 1993).

Distribution and population

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 (Olsen 1998), 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 (Garnett (Ed) 1993). Population cycles appear to be linked to those of the principal prey, the plague rat Rattus villossimus, which has population explosions following high rainfall (Olsen 1995). 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 (Olsen 1995). These explosions in population and range rarely last for more than a year, after which the species's distribution again contracts (Garnett (Ed) 1993). 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 (Garnett (Ed) 1993).

Ecology

This is a largely nocturnal species (Garnett (Ed) 1993), hunting at night, and tending to rest in coolabah trees Eucalyptus coolabah during the day (Olsen 1995). It inhabits open or sparsely wooded country, usually in flocks, but also seen as pairs and singles (Johnstone and Storr 1998). They roost, nest and sometimes hunt in groups, and often form large noisy breeding colonies of up to a hundred individuals (Olsen 1995). They nest in the cooler months when the rats often reach their peak, with nesting peaking in July. The nest is an open platform of sticks from herbage and shrubs. They lay clutches of 2-7 eggs and the incubation period is thought to be 31 days. The age at fledging is five weeks. During a rat plague, pairs will produce several clutches in succession until the rat populations crash, and parents spend little or no time on post-fledging care. During this time the population may increase by ten fold very rapidly. Parents may abandon their chicks when the local rat population crashes (Olsen 1995). Rat populations are thought to be fairly secure, even in extremely dry years, and there is reportedly always a core population of rats present (D. Akers in litt. 2007). Plaguing house mice Mus domesticus are also an important food resource, and the species feeds on a variety of invertebrates (M. Mathieson in litt. 2007).

Threats

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 (Olsen 1995).

Conservation actions

Conservation Actions Underway
No targeted conservation actions are known for this species.

Conservation Actions Proposed
Monitor population fluctuations through regular surveys and analysis of ad-hoc sightings. Conduct research into the impact of cattle grazing on rat numbers. Study the impact of nest predation by cats. Consider control of cats at core breeding sites. Identify and protect sites used by the core population.

Identification

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 (Johnstone and Storr 1998).

Acknowledgements

Text account compilers
Taylor, J., Garnett, S.

Contributors
Akers, D., Mathieson, M.


Recommended citation
BirdLife International (2019) Species factsheet: Elanus scriptus. Downloaded from http://www.birdlife.org on 21/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/08/2019.