 Clinging
to a lichen-covered rock wall, a Rockrunner (left) briefly
basks in the African sun. An endemic to rocky habitats in Namibia in southwestern
Africa, this interesting and unique bird has long been an enigma. Just
a couple years ago, the usually practical Dickinson (2003) followed Olson
(1998) and merged this the Namibian endemic into the genus Chaetops
[Rockjumpers].
Many recent books and checklists even use the ridiculous name "Damara Rockjumper"
for Rockrunner. Nothing could be further from the truth. Rockjumpers
are an ancient African lineage whose only relative are the Rockfowl [Picathartidae],
and even they are separated by over 31 million years of evolution. In contrast,
Rockrunner evolved among the Old World warblers that split off from the
rest of the sylvids about 30 millions years ago (Beresford et al. 2005).
But perhaps we are getting ahead of the story . . .
The great Sylvoid assemblage is crumbling. Recent research, much of
it based on DNA analysis, has shown that the Old World Warblers [Sylviidae]
did not all evolve from the same ancestor. Indeed, the 400 or so species
once considered Old Warbler Warblers may actually belong to a half-dozen
different lineages which may, pending further research, warrant family
status. Already we know that the genus Sylvia (with its whitethroats
and numerous 'warblers') are actually babblers (Sibley & Ahlquist 1990,
Barker et al. 2002). It is now generally agreed that the cisticolas and
allies [Cisticolidae] are a separate family of more than 100 species (Sibley
& Monroe 1990, Dickinson 2003). Even more recent studies have shown
that the megalurid grassbirds likely deserve family status [Magaluridae],
as do a set of Malagasy
Warblers (e.g., Cibois 1999, 2001, Schulenberg 2003, Barker et al.
2004). These changes had pared down the 400+ "Old World Warblers" to about
225 species.
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 Now
a new study (Beresford et al. 2005) sets apart yet another group: 17 species
of African warblers in 6 genera, about half of which are crombecs. My photo
(right) shows a Red-faced Crombec.: The apparent grouping
includes 9 species of Crombec (Sylvietta), 4 species of longbill
(Macrosphenus), Cape Grassbird Spenoeacus afer, Rockrunner
Achaetops pycnopygius, Victorin's Warbler Cryptillas victorini
(formerly placed in genus Bradypterus), and, by inference from prior
Sibley & Ahlquist (1990) work, African Mustached Warbler
Melocichla
mentalis. This may not turn out to be the exact parameters of this
group which Beresford et al. (2005) call the "Spenoeacus group."
Indeed, those authors do not yet split this off as a family. Yet the handwriting
is on the wall and, although this assignment is somewhat premature, world
birders should recognize that there is this unique group of African warblers.
This new grouping of African warblers is an eclectic assemblage of birds, and not anticipated. Beresford et al. (2005) noted it was "not predicted" by traditional classifications. It is, they say, a "novel clade [that is] relatively basal within the Sylviodea, [and] sister to more than 1000 species" of Old World passerines. They did not propose a family name. Christopher Tayler tells me that Macrosphenidae Wolters 1983 is available, so that is tentatively used here. Interestingly, the genus Macrosphenus is usually considered to consist of five species, but one of them, Kretschmer's Longbill M. kretschmeri, is actually a bulbul (Alström et al. 2006). Yellow Longbill M. flavicans, however, is among the African Warblers (Beresford et al. 2005) and the genus Macrosphenus was created for it in 1859. Thus Macrosphenidae would be an appropriate name for a family, should further research confirm the distinctiveness of this group. Half of this new group are crombecs. All crombecs are short-tailed and
rather short-billed active birds of a variety of wooded habitats. A number,
like Red-faced Crombec, are well adapted to dry thorn-scrub, but some might
be labeled as "forest crombecs," preferring mixed-species flocks in central
African lowland rainforests. The four species of longbills are mostly forest
birds with longer bills and tails than crombecs, and mostly very drab in
plumage. They tend to be shy but vocal.
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The remaining four genera are a diverse bag of African endemics. The
Cape Grassbird (below) is a shy songster of unique fynbos habitat around
Cape Town, South Africa.
 The Rockrunner (top photo) is an elusive rock specialist of arid northern Namibia than might recall a grasswren (Amytornis) of Australia. Victorin's Warbler, traditionally placed with many other species in Bradypterus, is another Cape of Good Hope vicinity endemic. It lives in pairs in thick undergrowth along gulleys and streams, and is loud and vocal, but is exceptionally difficult to see as in runs mouse-like through the thickets. The African Moustached Warbler is another shy songster, but living in east Africa where it frequents thick cover and rank herbage along streams from sea-level up to 2500m elevation. It (like Cape Grassbird) is a mimic with a loud carrying vocal repertoire. This grouping of African warblers is so new and so unexpected that nothing has yet been published about them as a group. Time will tell whether this unique group even holds together under peer analysis. For the moment they represent an interesting set of 'African enigmas' for world birders to acknowledge. |
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Photos: The Rockrunner Achaetops pycnopygius was responding to tape playback in Waterberg NP, northern Namibia, on 27 July 2005. The Red-faced Crombec Sylvietta whytii was in Tarangire Nat'l Park, Tanzania, on 27 July 2002. The Cape Grassbird (sometimes called Cape Grass Warbler) Spenoeacus afer was at Jonker Dam near Nordhoek, South Africa, on 3 July 2005. All photos © 2005 Don Roberson; all rights reserved. Bibliographic notes There is no "family book" covering the Africa warblers; indeed, as pointed out above, there is not yet a scientific consensus that this is a family. It is believed that Volume 11 in the Handbook of the Birds of the World series, due out next year, will treat them as Old World Warblers 'Sylviidae,' but for convenience only. 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. |