Long-billed tailorbird  (Artisornis moreaui)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

The long-billed tailorbird is a small, rather robust warbler, aptly named for its very long, slender beak. The plumage is greyish-brown in colour, paler on the underparts, and usually with a warm brown tinge on the face and crown. The beak is dark grey to black, and the legs and feet are greyish, while the long tail is typically held cocked (2) (3). Long, fine, hair-like feathers, known as ‘filoplumes’, extend from the crown to the back of the head (2) (3), although the significance of these is unknown (2). Male and female long-billed tailorbirds are similar in appearance, while the juvenile lacks the brownish head, and has darker grey underparts (2). 

Two subspecies of long-billed tailorbird are recognised: Artisornis moreaui sousae is smaller and darker than Artisornis moreaui moreaui, and has a more extensive brown tinge over the head and face (2). The species is distinguished from the similar-looking African tailorbird, Artisornis metopias, by its much longer beak, longer tail, and significantly less extensive brown colouration on the face and mantle (2) (3). The song of the long-billed tailorbird is described as a repeated, almost metallic tcheu or t’wee note, varying slightly in pitch (2) (3). A rasping contact call is also produced (2) (4).

The long-billed tailorbird is found in just two forests, 1,000 kilometres apart: A. m. moreaui occurs in the East Usambara Mountains in north-eastern Tanzania, and A. m. sousae in the Njesi Plateau (Serra Jeci) in northern Mozambique (2) (3) (5), where it was recently rediscovered (6).

In the East Usambaras, this species inhabits submontane and montane forest at elevations of around 850 to 1,200 metres (with most records from 900 to 1,100 metres), and favours forest edges and large canopy gaps, with high densities of vines and climbers (2) (3) (4) (7) (8) (9). Although sometimes found in degraded forest, large forest fragments and in habitats buffering tea plantations, but close to forest, such as dense Lantana thickets (3) (4) (7), it apparently avoids areas frequently disturbed by humans, such as regularly burned agricultural fields (3). In Mozambique, the species is found at an elevation of around 1,500 metres, and appears to inhabit the forest canopy rather than gap or edge habitats (2) (3) (6).

The long-billed tailorbird is a highly secretive bird, usually foraging alone in tangles of understorey vegetation, through which it travels with fast and deliberate movements (2) (4). However, it may occasionally join mixed-species flocks (2) (3), and while foraging in trees covered in dense tangles of vines, may climb to 20 to 30 metres high (8). Additionally, it forages in the forest canopy in Mozambique (2) (3). The diet consists of invertebrates, probably insects, which are gleaned from the vegetation or obtained by thrusting the long beak into tightly packed foliage (2) (4) (8). 

The long-billed tailorbird is believed to be territorial, with individuals potentially maintaining the same territory over a number of years. However, little else is known about the breeding behaviour of this species (2) (3) (5). Newly fledged young have been observed in October to November, suggesting that the eggs are laid in early September to October, and in one case the young remained with the adults until mid-March. Territorial pairs have been recorded to call most frequently in October to November, indicating that breeding activity occurs during this period (2) (4). Although the nest of this species has not yet been reliably described (2) (4), it is likely to be similar to that of other tailorbirds, the group being named for the habit of using plant fibres or spiders’ webs to sew leaves together into a cone, inside which the nest is built (10).

The long-billed tailorbird is under threat from forest destruction and fragmentation, and although the extent of protected forest in the East Usambaras has increased in recent years, unprotected forest is still under pressure from mining, cultivation, pole-cutting and firewood collection (3) (5), and habitat degradation still continues even within Forest Reserves (11). In 2000, the population in the Amani Nature Reserve in the East Usambaras was estimated at just 150 to 200 (4), although more recent work suggests this may be a slight underestimate (7). The population in Nilo Nature Reserve, East Usambara Mountains, which was initially discovered in 1996 (9), is currently being investigated, and preliminary data suggest that the entire East Usambara population will be higher than previously thought (12). The population of the Njesi Plateau in Mozambique is unknown, but is likely to be small (2) (3) (6). 

Although the long-billed tailorbird may not be overly affected by disturbance within the forest, since it tends to favour canopy gaps, the introduced tree Maesopsis eminii may present a threat, as it regenerates very rapidly in forest gaps, quickly closing them. The removal of vegetation such as Lantana bushes bordering tea estates and its replacement with Eucalyptus plantations may also remove potential habitat (7). The species’ low population density, its restriction to just two sites, and the small amount of suitable remaining habitat make the long-billed tailorbird particularly vulnerable to extinction, although there are hopes that it may yet be found in other forest areas in the region (3).

A number of conservation efforts are underway in the East Usambaras, where the long-billed tailorbird currently occurs in at least two protected areas, the Amani Nature Reserve and the Nilo Nature Reserve (2) (3) (9) (11). Projects are underway to increase the amount of forest in protected areas, and the Amani Nature Reserve in particular has an active conservation programme (3) (5). Additional conservation actions for the species include a population monitoring programme, extensive field surveys, educational programmes, and the recording and monitoring of every known tailorbird territory (3). These conservation initiatives are being conducted by the Wildlife Conservation Society of Tanzania, a BirdLife partner, in close collaboration with the management of Amani and Nilo Nature Reserves and other stakeholders (12). 

Although the species’ habitat in Mozambique is currently relatively undisturbed by humans, steps to formally protect the area have been recommended, and more extensive surveys may be performed in the region in the future (3) (5) (6). Other recommended conservation measures include searching for the species in areas in between its current two known locations, as well as performing ecological studies to determine why it is apparently so rare (3) (5). The effectiveness of different forest-management techniques should also be evaluated (3), particularly as this species may not benefit from strategies that eliminate all types of disturbance from the forest (7).

To find out more about conservation in Tanzania see:

• Eastern Arc Mountains Conservation Endowment Fund:
  http://www.easternarc.or.tz/
• Tanzania Forest Conservation Group:
  http://www.tfcg.org/

For more information on conservation efforts for the world’s most endangered bird species see:

• BirdLife International Preventing Extinctions Programme:
  http://www.birdlife.org/action/campaigns/species_champions/index.html