a confusion of by dfgh4bnmu


									                                         a confusion of
                                                                                                                                                             the most recent genetic studies of buteos
                                                                                                                                                             (buzzards), some species (for example,               Left The fledged juvenile buzzard seen
                                                                                                                                                             Forest and Steppe buzzards) have only                in Tokai, 2002.
                                                                                                                                                             recently diverged from one another, so,
                                                                                                                                                             in terms of their evolutionary history,              Below The adult rufous buzzard on
                                                                                                                                                             they are very closely related. There is              the nest in Tokai, 2003.
                                                                                                                                                             therefore a fair probability that the two
                                                                                                                                                             could hybridise, given the right circum-
                                                                                                                                                             stances (such as breeding in the same
                                                                                                                                                             habitats in the same area).
                                                                                                                                                                In 2005, Rob Martin reported a
                                                                                                                                                             ‘strange’ pair of buzzards breeding in
                                                                                                                                                             a mixed oak wood in Grabouw in the
                                                                                                                                                             Overberg region of the Western Cape,

           Mystery surrounds buzzards                                                                                                                        where they raised one chick (in a black-
                                                                                                                                                             wood tree). The birds were very similar
                                                                                                                                                             in appearance to the Peninsula buz-

           breeding in the Western Cape
                                                                                                                                                             zards, and both had solid rufous chests.                                          a n n ko e s l a G ( 2)

                                                                                                                                                             In 2006, a similar-looking pair attempt-
                                                                                                                                                             ed to breed in the same general area
                                                                                                                                                             (in a pine this time), but this attempt
                                                                                                                                                             failed when their nest was blown out
                                                                                                                                                             of the tree during a storm. Rob recalls
                                                   TexT by OdeTTe CurTis & Ann KOeslAg                                                                       watching dark-coloured buzzards dis-
                                                                                                                                                             playing more than 20 years ago, but as
                                                                                                                                                             it was common belief that only Forest

                                                                           hat is the first thing that comes    parts. According to the fieldguides,         Buzzards bred in the region, he dis-
                                                                           to mind when you come across         Steppe Buzzards are also usually silent      missed any suspicion that they could
                                                                           a breeding buzzard in a stand of     in Africa.                                   be something else. And, while Steppe
                                                              trees? You think ‘Forest Buzzard’, right?                                                      Buzzards are supposedly silent in Africa,

                                                              Most of us don’t even bother to take a                n 2002, Ann Koeslag found a pair         the ‘mystery buzzards’ call regularly
                                                              second look at the birds, because if they             of ‘strange’ buzzards breeding in        during aerial and pursuit displays.
                                                              are breeding or even just sitting in a for-           the pine plantations of Tokai in            The breeding buzzard population in
                                                              est, we assume they are Forest Buzzards.          the Cape Peninsula and we agreed that        the Cape Peninsula has been on the
                                                                 Or are they? Distinguishing the differ-        there was very little chance that they       increase during the past few years. We
                                                              ent buzzard species is not easy, mostly           were Forest Buzzards: one was a solid,       are now aware of close to 10 pairs of 
                                                              because of the enormous variation in              dark chocolate-brown, the other was a
                                                              plumage that is so characteristic of the          solid rufous in colour, and both lacked
                                    n i co my B u r G h
                                                              buzzard group. Therefore most of us               white blotching. This was hardly the
                                                              have adopted the assumption that if it’s          typical white, blotchy appearance of a
                                                              breeding, it must be a Forest Buzzard and         Forest Buzzard, and was in fact far more
                                                              if it’s sitting on a pole in a wheatfield, it’s   typical of a Steppe Buzzard – a bird
                                                              a Steppe Buzzard.                                 which supposedly does not breed in the
                                                                 Forest Buzzards Buteo trizonatus are           Southern Hemisphere. The pair raised
                                                              generally whiter on the underparts than           a single chick in their pine-tree nest in
                                                              Steppe Buzzards B. vulpinus, with some            2002. The following year, the ‘mystery’
                                                              rusty-brown mottling, but no barring,             birds used the same nest, but this time
                                                              except on the thighs. Unless soaring,             both adults were solid rufous in colour.
                                                              they are generally found within and on            They raised two chicks. In 2005, a pair
                                                              the edges of forests. Steppe Buzzards are         of unknown buzzards moved into a
                                                              very variable in plumage characteris-             nearby stand of trees and built a nest
                                                              tics, with varying degrees of blotching,          in a large eucalypt, where they raised
                                                              streaking and barring on their under-             a single chick. On this occasion, one
                           T r e v o r ha r d a k e r ( 2 )
                                                              parts, and often with a pale band across          of the birds was again solid rufous,
Top and middle Typically plumaged                             the centre of the breast. In flight, the          while the second had the paler, blotchy                                      jessie wa lTon (2)

Forest Buzzards.                                              two species are very difficult to separate        appearance typical of a Forest Buzzard.        The ‘mystery buzzards’ from Grabouw
                                                              and often this can only be achieved                 We then suspected that the two appar-        (male, above and female, right), photo-
Above a clearly recognisable steppe                           by comparing their proportions and                ently different species could be hybridis-     graphed in 2005.
Buzzard.                                                      the type of streaking on the under-               ing, but was that possible? According to

48   mystery buzzards                                                                                                       africa – birds & birding         j u n e / j u ly 2 0 0 7                                           mystery buzzards                    49
                                                                                                  certain that they are not Forest Buzzards,
                                                                                                  making it very likely that we are dealing
                                                                                                  with a Northern Hemisphere species.
                                                                                                  If they are Steppe or other Palearctic-
                                                                                                  breeding buzzards, it wouldn’t be the
                                                                                                  first time that ‘Northern Hemisphere’
                                                                                                  birds have bred in the deep south. In
                                                                                                  the Western Cape, there are breeding
                                                                                                  populations of White Storks Ciconia
                                                                                                  ciconia, Booted Eagles Aquila penna-
                                                                                                  tus, European Bee-eaters Merops apiaster
                                                                                                  and Leach’s Storm-Petrels Oceanodroma
                                                                                                  leucorhoa. In addition, there have been
                                                                                                  breeding attempts by Common House-
                                                                                                  Martins Delichon urbicum and almost
                                                                                                  certainly by Sandwich Terns Sterna
                                                                                                  sandvicensis. Whether all these popu-
                                                                                                  lations started breeding here for the
                                                                                                  same reason is unknown: European
                                                                                                  Bee-eaters have been here for hundreds
                                                                                r oB sim m on s
                                                                                                  of years, whereas Leach’s Storm-Petrels
 Throwing a spanner in the works...          plantation-nesting buzzards there and,               were only discovered breeding in the
 the rufous ‘mystery buzzard’ nesting        of these pairs, at least 40 per cent contain         1990s, and may already be dying out
 on a cliff above kirstenbosch, 2006.        either one or two ‘mystery’ buzzards.                here as a breeding species. The differ-
                                               Although we suspect the birds are                  ence between these species and our
                                             Steppe Buzzards, not all of them are                 mystery buzzards is that their identifi-
                                             typical Steppes, either. Most of them                cation is confirmed beyond doubt!
                                             are solid rufous or chocolate-brown in                   We hope to confirm the identity of
                                             colour – not the classic ‘bibbed’ Steppe             these buzzards in the not-too-distant
                                             Buzzards one sees on roadsides. Thus, for            future through a genetic study. We would
                                             the moment, we continue to call them                 also like to know what proportion of our
                                             ‘mystery’ buzzards.                                  breeding buzzard population is in fact
                                                                                                  made up of ‘mystery’ or hybrid pairs.

                                                     o add to the confusion, in 2006              Do the birds overwinter here? And, if so,
                                                     a pair of ‘mystery buzzards’ was             is this a long-established phenomenon
                                                     found breeding on a cliff above              (as Rob Martin’s observations may sug-
                                             Kirstenbosch National Botanical Gardens,             gest) or a more recent one? What food
                                             just outside Cape Town. This was a little            resources are the birds using? Do they
                                             disconcerting, as Steppe Buzzards do not             differ from those used by Forest Buzzards
                                             characteristically breed on cliffs within            and should we expect an increase in
                                             their ‘normal’ breeding range. And these             the incidence of breeding ‘mystery’ buz-
                                             birds were breeding on a cliff, above                zards? At a more fundamental level,
                                             hundreds of hectares of apparently per-              why do some birds change their migra-
                                             fectly viable forest, begging the question           tion pattern and breeding location? Is
                                             ‘why’? The migratory Common Buzzard                  it a response to habitat change, climate
                                             B. buteo and Long-legged Buzzard B. rufi-            change, both of these factors combined,
                                             nus are much more likely to breed on                 or other factors? And if there is hybrid-
     ACKNOWLEDGEMENTS                        cliffs. But these species do not (as far             isation, what are the implications of
     Thanks to bill Clark, Phil Hockey,      as we are aware) migrate as far south as             this for the near-endemic Forest Buzzard
     Callan Cohen and Meidad goren for       South Africa, let alone breed here. Plus,            population? These are all questions that
     their comments on pictures/sightings    the mystery birds do not have the typi-              will take many seasons of fieldwork and
     of the birds; to Jessie Walton, André   cal appearance of either of these species.           much collaboration to unravel.          
     du Toit, and Peter and barbara Knox-    At this stage, we cannot be certain what
     shaw for their observations and         these birds are.                                       if you have any information or photographs
     access to land; and to rob Martin          This can only be determined through                 that could contribute to the buzzard story,
     and rob simmons for their valuable      genetic material; we have taken blood                  or if you would like to get involved, please
     contributions to the development of     samples from a single brood of chicks,                 contact Odette Curtis on ocurtis@botzoo.
     this study.                             but are still awaiting the results.                    uct.ac.za or fax (+27-21) 650 3295.
                                             Whatever they are, we are increasingly

50     mystery buzzards                                                                                         africa – birds & birding

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