Old World warblers are a large group of birds formerly grouped together in the bird family Sylviidae. The family held over 400 species in over 70 genera, and were the source of much taxonomic confusion. Two families were split out initially, the cisticolas into Cisticolidae and the kinglets into Regulidae. In the past ten years they have been the subject of much research and many species are now placed into other families, including the Acrocephalidae, Cettiidae, Phylloscopidae, and Megaluridae. In addition some species have been moved into existing families or have not yet had their placement fully resolved. A smaller family of warblers, together with some babblers formerly placed in the family Timaliidae and the parrotbills, are retained in a much smaller family Sylviidae.
Most Old World warblers are of generally undistinguished appearance, though some Asian species are boldly marked. The sexes are often identical, but may be clearly distinct, notably in the genus Sylvia. They are of small to medium size, varying from 9 to 16 centimetres in length, with a small, finely pointed bill. Almost all species are primarily insectivorous, although some will also eat fruit, nectar, or tiny seeds.
The majority of species are monogamous and build simple, cup-shaped nests in dense vegetation. They lay between two and six eggs per clutch, depending on species. Both parents typically help in raising the young, which are able to fly at around two weeks of age.
In the late 20th century, the Sylviidae were thought to unite nearly 300 small insectivorous bird species in nearly 50 genera. They had themselves been split out of the Muscicapidae. The latter family had for most of its existence served as perhaps the ultimate wastebin taxon on the history of ornithology. By the early 20th century, about every insectivorous Old World "songster" known to science had at one point been placed therein, and most continued to be so.
Only after the mid-20th century did the dismantling of the "pan-Muscicapidae" begin in earnest. However, the Sylviidae remained a huge family, with few clear patterns of relationships recognisable. Though by no means as diverse as the Timaliidae (Old World babblers) (another "wastebin taxon" containing more thrush-like forms), the frontiers between the former "pan-Muscicapidae" were much blurred. The largely southern warbler family Cisticolidae was traditionally included in the Sylviidae. The kinglets, a small genus in a monotypic family Regulidae, were also frequently placed in this family. The American Ornithologists' Union includes the gnatcatchers, as subfamily Polioptilinae, in the Sylviidae.
Sibley & Ahlquist (1990) united the "Old World warblers" with the babblers and other taxa in a superfamily Sylvioidea as a result of DNA–DNA hybridisation studies. This demonstrated that the Muscicapidae as initially defined were a form taxon which collected entirely unrelated songbirds. Consequently, the monophyly of the individual "songster" lineages themselves was increasingly being questioned.
More recently, analysis of DNA sequence data has provided information on the Sylvioidea. Usually, the scope of the clade was vastly underestimated and only one or two specimens were sampled for each presumed "family". Minor or little-known groups such as the parrotbills were left out entirely (e.g. Ericson & Johansson 2003, Barker et al. 2004). These could only confirm that the Cisticolidae were indeed distinct, and suggested that bulbuls (Pycnonotidae) were apparently the closest relatives of a group containing Sylviidae, Timaliidae, cisticolids and white-eyes.
In 2003, a study of Timaliidae relationships (Cibois 2003a) using mtDNA cytochrome b and 12S/16S rRNA data indicated that the Sylviidae and Old World babblers were not reciprocally monophyletic to each other. Moreover, Sylvia, the type genus of the Sylviidae, turned out to be closer to taxa such as the yellow-eyed babbler (Chrysomma sinense) (traditionally held to be an atypical timaliid) and the wrentit (Chamaea fasciata), an enigmatic species generally held to be the only American Old World babbler. The parrotbills, formerly considered a family Paradoxornithidae (roughly, "puzzling birds") of unclear affiliations also were part of what apparently was a well distinctive clade.
Cibois suggested that the Sylviidae should officially be suppressed by the ICZN as a taxon and the genus Sylvia merged into the Timaliidae (Cibois 2003b), but doubts remained. Clearly, the sheer extent of the groups concerned made it necessary to study a wide range of taxa. This was begun by Beresford et al. (2005) and Alström et al. (2006). They determined that the late-20th-century Sylviidae united at least four, but probably as many as seven major distinct lineages. The authors propose the creation of several new families (Phylloscopidae, Cettiidae, Acrocephalidae, Megaluridae) to better reflect the evolutionary history of the sylvioid group.
The Sylviidae, in turn, receive several taxa from other families. Nonetheless, the now-monophyletic family has shrunk by nearly 80% for the time being, now containing 55 species in 10 genera at least. It is entirely likely however that with further research, other taxa from those still incertae sedis among its former contents, the Timaliidae, the Cisticolinae, or even the Muscicapidae will be moved into this group.
True warblers (or sylviid warblers) and parrotbills. A fairly diverse group of smallish taxa with longish tails. Mostly in Asia, to a lesser extent in Africa. A few range into Europe; one monotypic genus on the west coast of North America.
Marsh and tree warblers or acrocephalid warblers. Usually rather large "warblers", most are olivaceous brown above with much yellow to beige below. Usually in open woodland, reed beds or tall grass. Mainly southern Asia to western Europe and surroundings ranging far into Pacific, some in Africa. The genus limits are seriously in need of revision; either most species are moved into Acrocephalus, or the latter is split up though there is presently insufficient knowledge as to how.
See Cibois et al. (2001)
Grass warblers and allies. Mid-sized and usually long-tailed species; sometimes strongly patterned but generally very drab in overall colouration. Often forage on the ground. Old World and into Australian region, centred on the Indian Ocean; possibly also one species in South America. A not too robustly supported clade that requires further study.
The black-capped donacobius, Donacobius atricapillus, which was long considered an aberrant wren or mockingbird is apparently quite closely related, and might possibly be considered the only American species of this family.
Typical bush warblers and relatives or cettiid warblers. Another group of generally very drab species, tend to be smaller and shorter-tailed than Megaluridae. Usually frequent shrubland and undergrowth. Continental Asia, and surrounding regions, ranging into Africa and southern Europe.
Leaf warblers or phylloscopid warblers. A group very variable in size, often vivid green colouration above and yellow below, or more subdued with greyish-green to greyish-brown plumage. Catch food on the wing fairly often. Eurasia, ranging into Wallacea and Africa.
African warblers. Also "Sphenoeacus group". An assemblage of usually species-poor and apparently rather ancient "odd warblers" from Africa. Ecomorphologically quite variable. Monophyly requires confirmation.
Taxa that have not been studied. Most are likely to belong to one of Sylvioidea families listed above. Those in the Australian-Pacific region are probably Megaluridae. These taxa are listed in the sequence used in recent years.
Entirely unrelated songbirds hitherto placed in Sylviidae
The Acrocephalus warblers are small, insectivorous passerine birds belonging to the genus Acrocephalus. Formerly in the paraphyletic Old World warbler assemblage, they are now separated as the namesake of the marsh and tree warbler family Acrocephalidae. They are sometimes called marsh warblers or reed warblers, but this invites confusion with marsh warbler and reed warbler proper, especially in North America, where it is common to use lower case for bird species.
These are rather drab brownish warblers usually associated with marshes or other wetlands. Some are streaked, others plain. Many species breeding in temperate regions are migratory.
This genus has heavily diversified into many species throughout islands across the tropical Pacific. This in turn has led to many of the resulting insular endemic species to become endangered. Several of these species (including all but one of the species endemic to the Marianas and two endemic to French Polynesia) have already gone extinct.
The most enigmatic species of the genus, the large-billed reed warbler (A. orinus), was rediscovered in Thailand in March, 2006; it was found also in a remote corner of Afghanistan in the summer of 2009. Prior to these recent sightings, it had been found only once before, in 1867.
Many species have a flat head profile, which gives rise to the group's scientific name. The genus name Acrocephalus is from Ancient Greek akros, "highest", and kephale, "head". It is possible that Naumann and Naumann thought akros meant "sharp-pointed".Blyth's reed warbler
The Blyth's reed warbler (Acrocephalus dumetorum) is an Old World warbler in the genus Acrocephalus. It breeds in temperate Asia and easternmost Europe. It is migratory, wintering in Bangladesh, India and Sri Lanka. It is one of the most common winter warblers in those countries. It is a rare vagrant to western Europe.Brown-flanked bush warbler
The brown-flanked bush warbler (Horornis fortipes), also known as the brownish-flanked bush warbler, is a species of bush-warbler belonging to the Cettiidae family. It was formerly included in the "Old World warbler" assemblage. It is found in South Asia.Cetti's warbler
Cetti's warbler , Cettia cetti, is an Old World warbler. It is a small, brown bush-warbler which breeds in southern and central Europe, north-west Africa and east southern temperate Asia as far as Afghanistan and north-west Pakistan. The bird is named after the 18th century Italian zoologist, Francesco Cetti. This species is very difficult to see because of its skulking habits.Cisticolidae
The Cisticolidae family of small passerine birds is a group of about 160 warblers found mainly in warmer southern regions of the Old World. They were formerly included within the Old World warbler family Sylviidae.
This family probably originated in Africa, which has the majority of species, but there are representatives of the family across tropical Asia into Australasia, and one species, the zitting cisticola, even breeds in Europe.
These are generally very small birds of drab brown or grey appearance found in open country such as grassland or scrub. They are often difficult to see and many species are similar in appearance, so the song is often the best identification guide. These are insectivorous birds which nest low in vegetation.Clamorous reed warbler
The clamorous reed warbler (Acrocephalus stentoreus) is an Old World warbler in the genus Acrocephalus. It breeds from Egypt eastwards through Pakistan, Afghanistan and northernmost India to south China, southeast Asia and south to Australia. A. s. meridionalis is an endemic race in Sri Lanka.Eurasian reed warbler
The Eurasian reed warbler, or just reed warbler (Acrocephalus scirpaceus) is an Old World warbler in the genus Acrocephalus. It breeds across Europe into temperate western Asia. It is migratory, wintering in sub-Saharan Africa.Hume's bush warbler
Hume's bush warbler (Horornis brunnescens) is a species of bush warbler (family Cettiidae). It was formerly included in the "Old World warbler" assemblage.
It is found in the Himalayas of Nepal and India.
It is formerly considered conspecific with the yellow-bellied bush warbler.
The name commemorates the British naturalist Allan Octavian Hume who worked in India.Icterine warbler
The icterine warbler (Hippolais icterina) is an Old World warbler in the tree warbler genus Hippolais. It breeds in mainland Europe except the southwest, where it is replaced by its western counterpart, melodious warbler. It is migratory, wintering in sub-Saharan Africa.Leaf warbler
Leaf warblers are small insectivorous passerine birds belonging to the genus Phylloscopus. The genus was introduced by the German zoologist Friedrich Boie in 1826. The name Phylloscopus is from Ancient Greek phullon, "leaf", and skopos, "seeker" (from skopeo, "to watch").Leaf warblers were formerly included in the Old World warbler family but are now considered to belong to the family Phylloscopidae, introduced in 2006. The family originally included the genus Seicercus, but all species have been moved to Phylloscopus in the most recent classification. Leaf warblers are active, constantly moving, often flicking their wings as they glean the foliage for insects along the branches of trees and bushes. They forage at various levels within forests, from the top canopy to the understorey. Most of the species are markedly territorial both in their summer and winter quarters. Most are greenish or brownish above and off-white or yellowish below. Compared to some other "warblers", their songs are very simple. Species breeding in temperate regions are usually strongly migratory.Lemon-rumped warbler
The lemon-rumped warbler or pale-rumped warbler (Phylloscopus chloronotus) is a species of Old World warbler in the family Phylloscopidae. It is found from the western Himalayas to central China.Locustellidae
Locustellidae is a newly recognized family of small insectivorous songbirds ("warblers"), formerly placed in the Old World warbler "wastebin" family. It contains the grass warblers, grassbirds, and the Bradypterus "bush warblers". These birds occur mainly in Eurasia, Africa, and the Australian region. The family name is sometimes given as Megaluridae, but Locustellidae has priority.The species are smallish birds with tails that are usually long and pointed; the scientific name of the genus Megalurus in fact means "the large-tailed one" in plain English. They are less wren-like than the typical shrub-warblers (Cettia) but like these drab brownish or buffy all over. They tend to be larger and slimmer than Cettia though, and many have bold dark streaks on wings and/or underside. Most live in scrubland and frequently hunt food by clambering through thick tangled growth or pursuing it on the ground; they are perhaps the most terrestrial of the "warblers". Very unusual for Passeriformes, beginning evolution towards flightlessness is seen in some taxa.Among the "warbler and babbler" superfamily Sylvioidea, the Locustellidae are closest to the Malagasy warblers, another newly recognized (and hitherto unnamed) family; the black-capped donacobius (Donacobius atricapillus) is an American relative derived from the same ancestral stock and not a wren as was long believed.Macrosphenidae
The African warblers are a newly erected family Macrosphenidae, of songbirds. Most of the species were formerly placed in the Old World warbler family Sylviidae, although one species, the rockrunner, was placed in the babbler family Timaliidae. A series of molecular studies of the Old World warblers and other bird families in the superfamily Sylvioidea (which includes the larks, swallows and tits) found that the African warblers were not part of the family Sylviidae but were instead an early offshoot (basal) to the entire Sylvioidea clade.Melodious warbler
The melodious warbler (Hippolais polyglotta) is an Old World warbler in the tree warbler genus Hippolais. It breeds in southwest Europe and northwest Africa. It is migratory, wintering in sub-Saharan Africa. This small passerine bird is a species found in open woodland with bushes. Three to five eggs are laid in a nest in a tree or a bush. This is a common bird in many parts of its wide range and the International Union for Conservation of Nature has rated its conservation status as being of "least concern".Millerbird
The millerbird (Acrocephalus familiaris) is a species of Old World warbler in the family Acrocephalidae. It has two subspecies, A. f. kingi and A f. familiaris. The latter, the Laysan millerbird, became extinct sometime between 1916 and 1923. The former, the critically endangered Nihoa millerbird, remains the only race left, inhabiting the small island Nihoa in Hawaiʻi, though it has since been reintroduced to Laysan. It is the only Old World warbler to have colonised Hawaiʻi, although there is no fossil evidence that the species ever had a distribution beyond these two islands.
Millerbirds form long-term pair bonds and defend territories over a number of years. Territories can be as large as 0.95 hectares (2.3 acres), although 0.19–0.40 hectares (0.47–0.99 acres) is more typical. Breeding occurs variably from January to September depending on food availability.Palau bush warbler
The Palau bush warbler (Horornis annae) is a species of Old World warbler in the family Cettiidae.
It is found only in Palau.Supercilium
The supercilium is a plumage feature found on the heads of some bird species. It is a stripe which runs from the base of the bird's beak above its eye, finishing somewhere towards the rear of the bird's head. Also known as an "eyebrow", it is distinct from the eyestripe, which is a line which runs across the lores, and continues behind the eye. Where a stripe is present only above the lores, and does not continue behind the eye, it is called a supraloral stripe or simply supraloral. On most species which display a supercilium, it is paler than the adjacent feather tracts.The colour, shape or other features of the supercilium can be useful in bird identification. For example, the supercilium of the dusky warbler, an Old World warbler species, can be used to distinguish it from the very similar Radde's warbler. The dusky warbler's supercilium is sharply demarcated, whitish and narrow in front of the eye, becoming broader and more buffy towards the rear, whereas that of the Radde's warbler is diffusely defined, yellowish and broadest in front of the eye, becoming narrower and more whitish toward the rear. The supercilium of the northern waterthrush, a New World warbler, differs subtly from that of the closely related (and similarly plumaged) Louisiana waterthrush. The Louisiana has a bicoloured supercilium which widens significantly behind the eye, while the northern has an evenly buffy eyebrow which is either the same width throughout or slightly narrower behind the eye.A split supercilium divides above the lores. In some species, such as the jack snipe, the divided stripes reconnect again behind the eye. In others, such as the broad-billed sandpiper, the divided stripes remain separate.A supercilium drop is a feature found on some pipits; it is a pale spot on the rear of the ear-coverts which, although separated from the supercilium by an eyestripe, can appear at some angles to be a downward continuation of the supercilium.Tailorbird
Tailorbirds are small birds, most belonging to the genus Orthotomus. While they were often placed in the Old World warbler family Sylviidae, recent research suggests they more likely belong in the Cisticolidae and they are treated as such in Del Hoyo et al.
One species, the mountain tailorbird (and therefore also its sister species rufous-headed tailorbird), is actually closer to an old world warbler genus Cettia.They occur in the Old World tropics, principally in Asia.
These warblers are usually brightly colored, with green or grey upper parts and yellow white or grey under parts. They often have chestnut on the head.
Tailorbirds have short rounded wings, short tails, strong legs and long curved bills. The tail is typically held upright, like a wren. They are typically found in open woodland, scrub and gardens.
Tailorbirds get their name from the way their nest is constructed. The edges of a large leaf are pierced and sewn together with plant fibre or spider's web to make a cradle in which the actual grass nest is built.Yellow-bellied warbler
The yellow-bellied warbler (Abroscopus superciliaris) is a species of bush warbler (family Cettiidae). It was formerly included in the "Old World warbler" assemblage.
It is found in Bangladesh, Bhutan, Brunei, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand, and Vietnam. Its natural habitats are temperate forests, subtropical or tropical moist lowland forest, and subtropical or tropical moist montane forest.