Desert warbler (Sylvia nana)

Also known as: African desert warbler, Asian desert warbler, desert whitethroat
Synonyms: Curruca nana
  
French: Fauvette naine
KingdomAnimalia
PhylumChordata
ClassAves
OrderPasseriformes
FamilySylviidae
GenusSylvia (1)
SizeLength: 11.5 cm (2) (3)
Weight7 - 10.6 g (2)

The desert warbler is classified as Least Concern (LC) on the IUCN Red List (1).

One of the smallest of the Sylvia warblers, the desert warbler (Sylvia nana) is a compact, rather dainty bird, yet, as its name suggests, it is adapted to live in harsh desert environments (2) (3). The male and female desert warbler are similar in appearance, with rather uniform sandy or greyish-brown upperparts, which contrast with the reddish-brown rump, upper-tail and central pair of tail feathers. The throat and underparts are paler buff or whitish in colour, and the rest of the tail feathers, when spread, show conspicuous blackish areas, contrasting with white on the outermost feathers (2) (3) (4). The wings are relatively short (2) (3). The desert warbler has a fairly long, pointed bill, which is yellowish with a dark culmen and tip. The yellow legs, yellow eyes and white eye ring of this species are also distinctive (2) (3) (4). Juvenile desert warblers resemble the adult, but may have slightly more creamy yellow underparts (2) (3).

The desert warbler has previously been split into two subspecies, Sylvia nana nana and Sylvia nana deserti (2). However, these are now often considered to be separate species (the Asian desert warbler, Sylvia nana, and African desert warbler, Sylvia deserti), based on their separate distributions, differences in their vocalisations, plumage, body size and migratory behaviour, and a lack of any known intermediate forms. The African desert warbler is distinguished by its more pinkish-brown upperparts, as well as by a less contrasting rump, whiter underparts, less black on the tail, and a more pinkish-yellow beak and legs (2) (3). However, the taxonomy of these two forms has yet to be confirmed (2).

The calls of the desert warbler include a short, harsh, rapid trill (‘krrrr’) or a sharp chee-chre-krrrr (2) (3) (4). The song, given from a perch or during a ‘song flight’, is a fast, musical warble, often starting with a rattle, followed by fluting notes and ending in a whistle. The song of S. n. deserti is more rich and varied than that of S. n. nana (2) (3).

The desert warbler occurs across Central Asia, the Arabian Peninsula and North Africa (2) (5). The two subspecies have quite separate distributions: S. n. nana breeds across Central Asia, from the Caspian Sea and Iran to southern Mongolia and northwest China, and winters from northeast Africa, across the Arabian Peninsula to India, while S. n. deserti breeds in northwest Africa, from Western Sahara to Libya, and only undertakes some limited migration within this range (2) (3). S. n. nana is also sometimes recorded in Europe, outside of its usual range (2) (3) (4) (5).

As its common name implies, the desert warbler inhabits desert and semi-desert, as well as steppe, in areas with scattered low scrub and grasses. It is usually found in sandy terrain, but sometimes also in stony areas (2) (3) (4).

The desert warbler forages on the ground, around the bases of bushes, or in low cover (2) (4). It typically moves around in short, sharp hops, by running or by flying low between bushes (3), and has a distinctive habit of frequently raising and slightly fanning the tail (3) (4). This species commonly forages in association with the desert wheatear (Oenanthe deserti) or other bird species, probably to take advantage of prey disturbed by these other birds, or to benefit from early warnings against predators (2) (3). The diet consists predominantly of small insects and other invertebrates, although the desert warbler will also eat some seeds and berries (2) (3).

The desert warbler is territorial during the breeding season, and is believed to be monogamous (2) (3). It is the male that builds the nest, after first constructing simple ‘display nests’ as part of courtship. The nest used for breeding is deeper and more robust, built up to a metre above ground in low scrub and constructed from grass stems, twigs and leaves, and lined with grasses, fibres, spider webs and feathers (2) (3). The desert warbler lays between two and six eggs (fewer in S. n. deserti than in S. n. nana), which are incubated by both the male and female. The hatching period is not known, but is likely to be similar to other Sylvia warblers (2) (3). While S. n. nana breeds between April and July, S. n. deserti starts breeding from January to early March in the south of its range, and from late February to May further north (2) (3).

Overall, the desert warbler has a large range, is relatively common in suitable habitat, and is not currently considered to be globally threatened (2) (3) (5). However, in parts of the Sinai Peninsula, the desert warbler’s habitat has been reduced by drought and by overgrazing by goats, while in parts of the Middle East its habitat is threatened by agricultural intensification (2). In the deserts of Central Asia, the main threats to the desert warbler’s habitat are the spread of agriculture, overgrazing, and the overcutting of vegetation for firewood (6). S. n. deserti has a more restricted and localised range and a smaller population than S. n. nana (2) (3), and so may be more vulnerable to any potential threats.

There are not known to be any specific conservation measures in place for the desert warbler. However, it is listed on Appendix II of the Convention on Migratory Species (CMS), which aims to undertake conservation actions for migratory species throughout their range (7). The taxonomy of this species may need to be resolved, as some consider S. n. nana and S. n. deserti to represent separate species (3), which could potentially each face its own conservation issues.

To find out more about the desert warbler, see:

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  1. IUCN Red List (October, 2010)
    http://www.iucnredlist.org/
  2. del Hoyo, J., Elliott, A. and Christie, D. (2006) Handbook of the Birds of the World. Volume 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona.
  3. Shirihai, H., Gargallo, G. and Helbig, A.J. (2001) Sylvia Warblers. Christopher Helm, London.
  4. Peterson, R.T., Mountfort, G. and Hollom, P.A.D. (1993) Collins Field Guide: Birds of Britain and Europe. HarperCollins Publishers, London.
  5. BirdLife International (November, 2010)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=8079&m=0
  6. WWF: Central Asian southern desert (November, 2010)
    http://www.worldwildlife.org/wildworld/profiles/terrestrial/pa/pa1312_full.html
  7. Convention on the Conservation of Migratory Species of Wild Animals (November, 2010)
    http://www.cms.int/