 The
Megalurid Warblers — which might be known as the Grassbirds — are a group
of skulking, grass or thicket-loving birds. They include various birds
called "grassbirds," including Striated Grassbird (left), a widespread
species of south Asia, the Philippines, and Java. They are one of 10 or
more evolutionary lineages that are now recognized with the
break-up of the Old World Warblers ["Sylviidae"]. Alström et al.
(2006) formally proposed the name Megaluridae for "clade C" in their biochemical
study of the Sylviodea superfamily. They and others (e.g., Jønsson
& Fjeldså 2006, Barker et al. 2004) have shown this is a distinctive
lineage but the exact parameters of it are not yet known. It includes birds
currently assigned to genera Megalurus [various grassbirds and thicketbirds],
Bradypterus
[bush-warblers], Locustella [grasshopper-warblers],
Cincloramphus
[songlarks], and Schoenicola [fan-tailed warblers], and quite possibly
some other genera assigned to the Megalurid 'subfamily' by Sibley &
Monroe (1990) and Dickinson (2003). Together this is about 50 species in
about a dozen genera, but DNA results are not known from quite a few of
these. Alström et al. (2006) and Jonsson & Fjeldså (2006)
both shown that the genera Megalurus, Bradypterus, and Locustella
are non-monophylectic [i.e., they are not distinct evolutionary lineages
as currently composed], so we can anticipate many changes in the assignment
of species in the future.
The DNA evidence shows that the Megalurid Warblers are a sister group to the Malagasy Warblers and together those two groups are a sister group to the Acrocephalid Warblers (Jønsson & Fjeldså 2006). There are various ways to approach this situation. I prefer to consider the three distinct groups as three families, but some may lump the Malagasy Warblers, and those 11 species, into the Megaluridae, giving it two subfamilies. These things will be sorted out over time. |
 DNA
work has apparently not yet been done on various grassbirds in the south
Pacific. Assuming these are, indeed, grassbirds, the one that reached New
Zealand is Fernbird (right). It is the only sylvioid warbler to
reach New Zealand; the two other "warblers" are gerygones in the unrelated
Australasian Warbler family [Acanthizidae]. Fernbirds are secretive but
inquisitive birds of swamps and scrub, widely distributed on the main New
Zealand islands. They are most often found by the metallic uu-tick
calls; a mechanical double-call duet is given by mated pairs (Heather &
Robertson 1996). I was able to get this shot when one responded to a rather
poor tape-recording I had available.
Grassbirds (genus Megalurus and similar genera) are found on all the Old World continents (one in Africa, five on mainland Asia, five on Australia, including two songlarks Cincloramphus) but they are most heavily distributed on islands. Madagascar and New Zealand each have one, and New Guinea has three, and there are endemics on Timor (Buff-banded Grassbird in the monotypic genus Buettikoferella), on New Caledonia (the elusive Megalurulus mariei that had been hinted to be extinct until recently), Fiji (Long-legged Thicketbird Megalurulus rubiginosus) and two on New Britain and the Solomons (Melanesian and Rusty Thicketbirds). I think all of them are serious skulkers. Again, whether all of these is actually within this evolutionary radiation has yet to be determined, and there will be changes in assignment to genus among these in the future. |
 Two
more significant groups of hard-to-see skulkers are in the Megaluridae:
the Bradypterus bush-warblers and scrub-warblers, and the Locustella
grasshopper-warblers. An example of Bradypterus is Southern Spotted
Bush-Warbler (left) of the mountains of central Asia. On my China trip
we had one walking about just inches from our shoes in thick scrub one
morning, but of then ten of us, only one caught a glimpse of it. Then,
two days later, we worked with tapes for another hour before he popped
up for quick views. Yet, the next morning, this male (left) decided to
sit atop a flowering bush and sing for ten minutes straight! Truly inexplicable.
Another one that made an impression on me was the Dja River Scrub-Warbler Bradypterus grandis in Gabon. It was once known only from a few specimens near the Dja River in Cameroon, and totally unknown in the wild. Shortly before my trip to equatorial Africa in 1996, Patrice Christy found a small population in a Rhynchospora marsh in La Lopé Reserve, Gabon, and he showed us its display flight there in July 1996 (we were the first American birders to enjoy this treat). It took repeated playing of its song to get quick glimpses in dense aquatic vegetation, but in due time it took up some display flights on its own, bursting into the air from a song-filled glide down into the marsh. Special.... The various Locustella warblers are also extreme skulkers. Lanceolated
Warbler L lanceolata has a wide range in eastern Asia, and migrates
to south Asia (indeed, a vagrant has reached California!), but is well
known for behaving like a mouse.
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| Cibois et al. (2001) point out that the large corvoid radiation in Australasia had been hidden by convergence for centuries and was only discovered through the biochemical DNA-DNA studies of Sibley & Ahlquist (1990) and progeny. It is exciting to learn that other radiations — this time of sylvioid warblers — have been hidden by convergence. A 'Malagasy clade' of at least 9 million years old has only recently been identified (Cibois et al. 1999, 2001, Barker et al. 2004). The Megalurids represent yet another 'hidden' assemblage just now being discovered through biochemical research. I look forward to the time when a lot more information is available about these grassbirds, whatever their final taxonomic status may prove to be. |
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Photos: The Strated Grassbird Megalurus palustris was singing from riverine scrub on Mindoro I., the Philippines, on 7 Dec 2005. The Fernbird Megalurus punctatus was in a marsh at the edge of Lake Taupo, North Island, New Zealand, in Dec 1997. The Southern Spotted Bush-Warbler Bradypterus przewalskii was at 8000' elevation in Huzu Bei Shan Nat'l Park, Qinghai Province, China, in June 2004. All photos © 2006 Don Roberson; all rights reserved. Bibliographic notes There is no "family book" covering the megalurid warblers (grassbirds) so information must be sought out in a variety of texts. The next volume of HBW will cover all the sylvioid warblers. Literature cited: Alström, P., P.G.P. Ericson, U. Olsson, and P. Sundberg. 2006. Phylogeny and classification of the avian superfamily Sylvioidea. Molecular Phylogenetics & Evolution 38: 381-397. |