Straight-billed reedhaunter (Limnoctites rectirostris)

Synonyms: Limnornis rectirostris
GenusLimnoctites (1)
SizeLength: 16 cm (2)

Classified as Near Threatened (NT) on the IUCN Red List (1).

After its discovery by Charles Darwin in 1833, this species became known as “Darwin’s lost bird”, as it took almost a century before further specimens were located (3) (4). The straight-billed reedhaunter is slender-bodied, with greyish-brown upperparts, becoming greyer on the crown, and with an indistinct whitish band running above the eye. By contrast, the wings and long, pointed tail are reddish-brown, while the underparts are white becoming buff on the flanks (2) (5). Perhaps the most distinctive feature of the straight-billed reedhaunter is the very long, straight bill (5), which may be an adaptation for extracting insect prey from amongst the leaves and flower heads of spiny plant species (3).

The straight-billed reedhaunter has a relatively small range, extending from the states of Santa Catarina and Rio Grande do Sul in extreme southern Brazil, through to southern Uruguay and eastern Argentina in the provinces of Entre Ríos and extreme north-east Buenos Aires. Within this range, the straight-billed reedhaunter is very sparsely distributed, but is locally common in appropriate habitats (2).

The straight-billed reedhaunter is most commonly found in marshland, but also occupies stands of short trees and shrubs bordering wet areas up to elevations of 1,100 metres. This species has a close association with the spiny herb commonly called caraguata (Eryngium species), which grows around marshes and in upland thickets (2).

Usually seen in pairs, the reclusive straight-billed reedhaunter spends most of the day concealed amongst dense, low vegetation. It will, however, move to a more exposed perch during territorial displays, when it produces a series of high-pitched notes ending in a trill, tsi-tsi-tsi-tsi-tsi-tititititititi (3) (5).

Little is known about the reproductive behaviour of the straight-billed reedhaunter, but it is known to lay an average of three eggs in a dome-shaped nest situated within vegetation (3).

The major threat to the straight-billed reedhaunter is habitat degradation and clearance as a result of human development. This is particularly problematic in the heavily populated province of Buenos Aires, where house-building, rubbish dumping and water pollution are threatening to destroy the remaining areas of marshland that this species occupies. In other areas, its habitat is also threatened by intensive grazing, marsh drainage, and plantations of Eucalyptus and pine species, which have a drying effect on the surrounding land (2).

In order to gauge the current level of decline of the straight-billed reedhaunter population, further surveys must be undertaken. In addition, efforts should be made to increase protection of this species’ habitat, through the designation of protected areas (2).

The conservation organisation, Aves Argentina, is working to ensure that important bird habitats within Argentina are properly conserved and protected. This includes assisting in the management of Otamendi Nature Reserve, which contains the only known breeding population of the straight-billed reedhaunter, and is one of the few places in its range where it receives protection (6) (7).

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  1. IUCN Red List (July, 2014)