Just got my copy of Bull.B.O.C. for March 99. For those who don't get
this excellent publication, there are a number of very interesting papers.
A new species Garrulus ngoclinhensis,Golden-winged Laughingthrush,
Garrulus ngoclinhensis Eames,Le Truong Trai & Nguyen Cu,1999,Bulletin of
the British Ornithologists' Club,119,1,p.6. (Mount Ngoc Linh[15deg04'N
107deg59'E],Kon Tum Province,Vietnam at c.2200m asl.)
A new subspecies of Camptostoma imberbe, Northern Beardless Tyrannulet:
Camptostoma imberbe thyellophila Parkes & Phillips,1999,Bulletin of the
British Ornithologists' Club,119,1,p.60. (11 km SW of San Miguel,Isla
Cozumel,Quintana Roo,Mexico).
Parkes pp.65-68, on the status of Barred Woodcreeper Dendrocolaptes
(?certhia) sanctithomae in the Yucatan Peninsula, rejects D.certhia
legtersi Paynter,1854, and also says that the range of sanctithomae will
have to be extended north to Pacific Chiapas.
Clark,on pages 56-59, reconsiders the status of Circaetus
gallicus,pectoralis, and beaudouini. These were treated as conspecific by
Peters,1931,Brown & Amadon,1968,Stresemann & Amadon,1979, Brown,Urban &
Newman,1981(Birds of Africa,1) and Amadon and Bull,1988, while others (most
recently Cramp & Simmons,1980,Birds Western Palearctic Vol.2) have split
them, mainly on the bases of plumage differences.
Most of the lumpers offer no evidence, but Brown,1974,reported five
instances of interbreeding: 2 pectoralis x beaudouini, 2 beaudouini X
gallicus and 1 gallicus x pectoralis in support of a single species.
Clark comments that none of Brown's claimed examples is reliable, as all
can be explained in terms of a subadult plumage of C.pectoralis.
He notes that Hellbig and Siebold (pers.comm.) have compared the
mitochondrial DNA of pectoralis and gallicus and found their differences to
be well above species level, and recommends that all three in the meantime
be treated as separate species.
It occurs to me that even if Brown's identifications had been correct, the
five supposed interbreedings would not necessarily constitute strong
evidence for conspecifity. Modern population dynamics pays attention not
just to the occurrence of interbreeding but also to its frequency. For
example, if, in a zone of overlap between two taxa, 50 percent of breeding
pairs were mixed, this would be at least prima facie evidence for
conspecifity. But if only 1 or 2 % of breeding pairs were mixed, this
would be evidence of strong separation between taxa. After all, 1 and 2
are much closer to 0 than to 100. So I would not have attached great
significance to a few scattered pairings in the first place!
John Penhallurick
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