The Cape Bird Club

Enigma: Cracking the ‘Mystery Buzzard’ code by  Lisle Gwynn.
                                                                                    
                             Percy FitzPatrick Institute.

an extract article from Promerops No 288, November 2011.

 

The story of the Western Cape’s ‘mystery’ buzzards has appeared in South African literature at least twice in recent times (Curtis & Koeslag, 2007, Martin & Walton 2010). Our investigation began in earnest with a pair of ‘strange’ buzzards breeding in the pine plantations of Tokai in 2002. However, Peter Steyn’s breeding buzzards on the Peninsula in the 1960s could well mark the first documentation of what has become an intriguing and as yet unexplained phenomenon.

In the agricultural lands surrounding Grabouw, even the local farmers know of ‘the red buzzards’ and remark on their abrupt appearance and abundance. With confirmed records in the area from the late 1980s onwards, these ‘mystery’ buzzards are now the most abundant raptor in the area, breeding in exceptional density across the landscape characterised by alien pine and eucalypt plantations. They have even earned themselves a name in the local community - Elgin Buzzards.

The ‘mystery’ buzzards are, as is typical of the genus Buteo, highly variable in appearance. They range from birds with tear-drop markings on their breasts, similar to ‘typical’ Forest Buzzards Buteo trizonatus, all the way to heavily barred individuals that resemble ‘typical’ Steppe Buzzards (B. b. vulpinus). The majority of them, however, are uniformly coloured below. These uniform rufous and ‘chocolate’ morphs are unknown in either Forest or Steppe Buzzard, with the former showing rather little plumage variation, and the latter always being barred, at least to some extent, even in the most uniform of ‘Fox Red’ morphs.


photograph by Ann Koeslag                                 photograph by Graham Pringle

Forrest Buzzard.                                 Steppe Buzzard.

Uniform morphs are, however, prevalent among a little-known Middle Eastern race of Common Buzzard B. b. menetriesi, or ‘Ménétries’s Buzzard ‘, also called ‘Eastern Steppe Buzzard’. This close ally of the Palearctic-breeding Common Buzzard B. b. buteo is found from the southern Crimea and Caucasus to Caspian Iran. Although considered by some as sedentary, its migratory patterns are, at best, debatable. Another anomaly of the ‘mystery’ buzzards lies in the pair that nested on a cliff ledge above Kirstenbosch in 2006. Cliff-nesting is unknown in either Steppe or Forest Buzzard, but is frequent in both Common Buzzard and ‘Ménétries’s’ Buzzard, and in Long-Legged Buzzard both in the nominate (B. rufinus rufinus) and the smaller North African/Arabian race (B. r. cirtensis). It is also the sole nesting habitat of the ‘Socotra Buzzard’ (B. socotraensis).

So what is the answer here? Are the birds Forest Buzzards (B. trizonatus)? This seems unlikely, given the absence of differently coloured morphs in the species’ core south coast range. Are they Steppe Buzzards that have undergone an unnoticed colonisation, coupled with hybridisation with the local Forest Buzzards, giving rise to a large diversity of colour forms? Based on what we know about the occurrence of different buzzard species in South Africa, this seems the most likely answer. Or are they something else? To resolve their identity, we will be using a combination of molecular techniques and ecological analysis. For this to be successful, however, we need your help.

Firstly, it is our aim to catch and take blood samples from as many ‘typical’ locally-breeding ‘mystery’ buzzards as possible.
Here, we ask you to please visit http://mysterybuzzard.blogspot.com  and familiarise yourself with the Elgin Buzzard and to report any sightings (coupled with photographs if possible)
to: lisle.gwynn@uct.ac.za 
This will allow us to increase our potential sample size, and to begin to map the current range of the birds. The current range extends at least from the Cape Peninsula east to Swellendam, but there are records that could refer to Elgin Buzzards from as far east as Port Elizabeth.

Secondly, the existing samples of Forest Buzzard DNA, with which to compare our buzzards, are very few. The aim is to sample from as many Forest Buzzards as possible: the most reliable way of doing this will be by sampling from chicks at nests (this is a wholly non-destructive sampling technique). Forest Buzzards are cryptic and secretive when breeding, but nests can be and are found. It is also important for us that as many samples as possible come from the core of its range (around Knysna and eastwards). If you know of the location of any Forest Buzzard nest(s), please report these to the same email address as above.

Thank you for your help, and we look forward to being able to report on progress in the not-too-distant future!

                                                                                                                                                

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