|The Wirebird is the last surviving endemic bird on St Helena. A few
fossil bones of the species have been found in the most recent and middle
period deposits, implying that it has been evolving on the island for
at least several thousand years. Although it is closely related to Kittlitz's
Plover of southern Africa, there are interesting differences. The Wirebird
is substantially larger (length 19 cm) and has longer legs and bill, more
rounded wings and relatively smaller flight muscles. The latter features
are often found among birds on oceanic islands and sometimes culminate
evolutionarily in the loss of flying ability. The Wirebird, however, is
a capable flyer over the short distances required for life on St Helena.
This flying ability may have been crucial in enabling the Wirebird to
survive in the presence of feral cats.
Wirebirds (especially males) defend territories throughout the year, though most aggressively in the breeding season, which is mainly in the period October to March. The nest is an unlined shallow depression on the ground. Two eggs are normally laid and are grey to green with darker blotches; they average 34 x 25 mm. Incubation is about 28 days and the young can fly at four to five weeks. The incubating bird, when disturbed, will often partly cover the eggs with loose material before leaving the nest. If a person approaches the nest the bird will sometimes use a 'distraction' display, with trailing wing and spread tail, and may even collapse on the ground in a rumpled mass of feathers.
The Wirebird received remarkably little scientific attention until recently. Arthur Loveridge made a series of detailed behavioural observations, but it is only with the systematic work by Neil McCulloch in 1988-89 that a full picture of the biology of this intriguing species has emerged. McCulloch spent most of his time censusing the population and assessing its future prospects. He estimated that there were rather less than 500 individuals, with highest densities on relatively dry, flat pastures; the best areas were Bottomwoods, Longwood Golf Course and Farm, and Deadwood Plain. The birds also occupy semi-desert areas and frequently visit places with caked mud along streams, for instance below Gregory's Battery near Turks Cap Ridge and in Fishers Valley; they also bathe and drink at the pools near Cook's Bridge. However, the future of the Wirebird is now inevitably linked to the maintenance of pasture land, since about four-fifths of the population live in this habitat.
The Wirebird feeds on surface living invertebrates, mainly beetles, caterpillars, crickets and grasshoppers. The most important single prey at present is the tenebrionid beetle Gonocephalum simplex,. This is among the most abundant beetle in dry parts of the island. It is notable that members of this group of beetles are very abundant in open country in southern Africa, so the ancestors of the Wirebird evidently found familiar prey available to them when they reached St Helena.
Many people have wondered about the habitat of the Wirebird on St Helena at the time when a large proportion of its current range was covered with trees. McCulloch pointed out that as a bird of open country it may have actually benefited from deforestation. Quentin Cronk suggested that it might have lived in the dry gumwood woodland, which lacked undergrowth, but this is a type of habitat not used by any other plover. It seems possible that during periods of high sea level like the present, the Wirebird was largely confined to the semi-desert area of Prosperous Bay Plain (where it still occurs in significant numbers) and to a few smaller level areas where there were only scattered bushes. During periods of lowered sea level, however, the Wirebird would have had a much larger population, since it would also have occupied the broad apron of flat sandy land that was then exposed around the fringes of the island. It is easy to imagine a group of exhausted and hungry vagrant sand-plovers from open, dry areas in Africa settling down in such a habitat to feed on tenebrionid beetles and the endemic snails. We suspect that these plovers established themselves on the island at such a time, and were then able to maintain at least a small population on and around Prosperous Bay Plain during the interglacial periods when the apron was inundated by the sea.