BIRD FAMILIES OF THE WORLD
 
 
a web page by Don Roberson
 
 
REED-WARBLERS & ALLIES Acrocephalidae
  • 56 species in the Old World
  • DR personal total: 19 species (34%), 6 photo'd

The Acrocephalidae is a new family created by the "break-up of the Old World warblers." The core of the family is the large genus Acrocephalus, many of them called reed-warblers, such as Eurasian Reed-Warbler (above). It was photographed during fall migration as is skulked through a Middle Eastern reedbed. Difficult to see at the best of time, Acrocephalus warblers become conspicuous only when in full song, like this Sedge Warbler on territory in a marsh in Spain (left, in a very fine shot by Blake Matheson).

Traditionally, this subset of the Old World warblers was comprised of four genera: Acrocephalus "reed-warblers," Hippolais "tree-warblers," Chloropeta "yellow-warblers" in Africa, and Nesillas "brush-warblers" in Madagascar and the Comoros. After extensive molecular review, Fregin et al. (2009) re-arranged the family conservatively, leaving the current composition of five genera: Acrocephalus "reed-warblers" (39 species), core Hippolais warblers (4 species), Iduna warblers (8 species that group together from 3 different former assignments, including two of the Chloropeta warblers; more below), Calamonastides (Papyrus Yellow-Warbler, formerly in Chloropeta), and the four Nesillas brush-warblers of Madagascar and the Comoros (plus another, N. aldabrana from Aldabra I., that is extinct).

Reed-warblers typically breed in extensive marshes, such as this one in Xinghai Nature Reserve, northeastern China (above). Oriental A. orientalis, Black-browed A. bistrigiceps, and Manchurian A. tangorum all breed in this marsh and, with effort, each of the skulking songsters was viewed reasonable well (but not without some wet feet). In contrast, there are places where other reed-warblers — like this Clamorous Reed-Warbler in the Baliem Valley in montane New Guinea (right) — walk up on a stalk into the open to sign vigorously when setting up territories.

Field identification of Acrocephalus warblers can be a major challenge. Literature used in China, for example, to sort out the rather local Manchurian Reed-Warbler, included Alström et al. (1991) and Leader & Lewthwaite (1996).

Acrocephalus once included "the least known bird in the world," some said when Large-billed Reed-Warbler A. orinus was known from a single specimen taken in n. India in 1867. This changed when a migrant was discovered in Thailand in 2006, and then the breeding grounds were discovered in northeastern Afghanistan (Timmons et al. 2012).

The DNA evidence now restricts Hippolais warblers to just four core species: Booted H. caligata, Melodious H. polyglotta, Olive-tree H. oivetorum, and Upcher's H. languida. The remaining four previous "hippos" are now assigned to genus Iduna, including Olivaceous Warbler (left), photo'd here as a migrant in Iran. It is now split from I. opaca, the Isabelline Warbler ("Western Olivaceous Warbler"). Genus Iduna now also includes Thick-billed Warbler, formerly "Acrocephalus" aedon, and two of the yellow-warblers of Africa: African Yellow-Warbler, now I. natalensis, and Mountain Yellow-Warbler, now I. similis. Papyrus Yellow-Warbler gets its own monotypic genus, and becomes Calamonastides gracilirostris; Fregin et al. (2009).

All of the Palearctic members of the Acrocephalidae are migrants, moving south of winter in African, India, or southeast Asia. Streaked Reed-Warbler Acrocephalus sorghophilus, for example, winters almost entirely in the Philippines, and is suffering declines as its wintering marshes are converted to cultivation. Tropical populations are generally sedentary.

There are reed-warblers in the Indian Ocean, including Seychelles Reed-Warbler (right). This species has a very tiny range and nearly went extinct. There were only 29 individuals located in 1959, on a single tiny island — Cousin I. (29 ha in size). The island became a nature reserve in 1968 and habitat management led to increase in numbers: 323 birds by 1997, thought to be the island's capacity. Many breeding pairs had nest-helpers. Portions of the population were translocated to Cousine and Aride, where those populations are growing. It is one of the world's best success stories of saving a species from extinction.

There is also an impressive set of reed-warblers on islands in the Pacific, many of them island endemics. Cibois et al. (2011) used molecular evidence to evaluate western Pacific Acrocephalus and found a number of overlooked species. Sadly, Pagan Reed-Warbler A. yamashinae, Mangareva Reed-Warbler A. astrolabii, Leeward Islands Reed-Warbler A. musae and Moorea Reed-Warbler A. longirostris had already become extinct. Pacific Acrocephalus still extant include birds way out in the middle of the Pacific, including Millerbird A. familiaris of Nihoa I., Hawaii, and Pitcairn Reed-Warbler A. vaughani. Many of these island populations are threatened or endangered. What may be most fascinating about these oceanic-island reed-warblers is that they colonized the Pacific in at least three different waves of colonists. The DNA evidence (Cibois et al. 2011) shows that in some places, like the Marquesas, reed-warblers on islands only 41 km apart arose from completely different waves of immigrants, and thus each is more closely related to birds on islands thousands of miles distant than they are to the reed-warblers on the next island over.

There is still much to learn about the Acrocephalidae, including the actual number of species. Many east Asian, Melanesian, and west Pacific populations are poorly known. This family was recently evaluated for genetic distance between populations, and serves as a cautionary tale about the using genetic distance, and nothing else, to come to species level conclusions. Genetic distance is just part of the answer — it is not, standing alone, "the" answer as some who propose "bar-coding" suggest (Fregin et al. 2012).

 

Photos: The Eurasian Reed-Warbler Acrocephalus scirpaceus was at Sham-el-sheik, Sinai Peninsula, on 7 Nov 1981. Blake Matheson photographed the Sedge Warbler A. schoenobaenus at Rocio, Huelva, Spain, in March 2004. The habitat shot of Xinghai Reserve, Jilin, China, was taken on 13 June 2004. The singing Clamorous Reed-Warbler A. stentoreus in the Baliem Valley, Papua Province (formerly Irian Jaya), Indonesia, on 31 July 1994. The Olivaceous Warbler Iduna pallida was at Persepolis, Iran, on 9 Aug 1978. The Seychelles Reed-Warbler A. sechellensis was on Cousin I., Seychelles, on 13 Nov 1992. Photos © Don Roberson, except that attributed to Blake T. Matheson, used with permission; all rights reserved.

Bibliographic note: There is no "family book" per se, but information about the (now-revised) family, with all the species covered and with many photos, is in Bairlein (2006). The HBW account covered the entire "Old World warblers," before the break-up of the family, so the Acrocephalidae are only a portion of that account.

Literature cited:

Alström, P., U. Olsson, and P.D. Round. 1991. The taxonomic status of Acrocephalus agricola tangorum. Forktail 6: 3-13.

Bairlein, F. 2006. Family Sylviidae (Old World warblers), pp. 492 –712 in Handbook of the Birds of the World (del Hoyo, J., A. Elliott & D.A. Christie, eds). Vol. 11. Lynx Edicions, Barcelona, Spain.

Cibois, A., J.S. Beadel, G.R. Graves, , E. Pasquet, B. Slikas, S.A. Sonsthagen, J.-C. Thibault, and R.C. Fleischer. 2011. Charting the course of reed-warblers across the Pacific islands. J. Biogeogr. 38, 1963–1975.

Fregin, S., M. Hasse, U. Olsson, and P. Alström. 2009. Multi-locus phylogeny of the family Acrocephalidae (Aves: Passeriformes) -- the traditional taxonomy overthrown. Molec. Phylogen. Evol. 52: 866–878.

Fregin, S., M. Haase, U. Olsson, and P. Alström. 2012. Pitfalls in comparisons of genetic distances: a case study of the avian family Acrocephalidae. Molec. Phylog. Evol. 62: 319–328.

Leader, P.J., and R.W. Lewthwaite. 1996. Manchurian Reed Warbler: the first records for Hong Kong. Hong Kong Bird Rpt.1995: 119-122.

Timmins, R.J., S. Ostrowski. N. Mostafawi, J. Noori, A.M. Rajabi, L. Svesson, U. Olsson, and C.M. Poole. 2012. New information on the Large-billed Reed Warbler Acrocephalus orinus, including its song and breeding habitat in north-eastern Afghanistan. Forktail 26: 9–23.

 
 

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