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The Gib Buzzard conundrum

By Dick Forsman

I’m just back from a week’s tourleading and raptor watching around Tarifa, Spain, the southernmost town in Europe, just on the Strait of Gibraltar. And once again, I was reminded of the buzzard conundrum related to this area

Already in the 1990’s, when I started to visit this region regularly, I remember seeing reddish Common Buzzards, quite similar to the Steppe Buzzards of my native Finland and the Steppe Buzzards I see on migration in the Middle East. However, according to the literature and also according to my Spanish friends the Steppe Buzzard had never been officially recorded in Spain, it was not on the Spanish list. These were in the days of film cameras and it was difficult to get close enough to document these shy birds properly, and although I managed to shoot some, including some vagrant African Long-legged Buzzards, I could never get close enough to the more interesting individuals.

Then over a decade passed and knowledgeable birders moved to stay in this area. The buzzards were “re-found”, and not just the birds, even some nests were located. It was especially thanks to the work of Javier Elorriaga and Antonio-Roman Muñoz that this buzzard enigma was eventually solved. Their field work included trips across the Strait to northern Morocco and to the Spanish colony of Ceuta, on the southern shore of the Strait, where similar looking birds were known to breed.

In September 2012 the three of us together with two American birders made a trip across the Strait to look for these birds. In Ceuta we watched a breeding pair with fledged chicks and in Morocco proper we encountered several more. We had lengthy discussions on these birds, as Antonio and Javier were preparing a paper on their findings. The final conclusion was, that these birds were part of a hybrid population, hybrids and backcrosses between the African Long-legged Buzzard (aka Atlas Long-legged Buzzard) and Common Buzzards. Vagrant and migrant Common Buzzards from Europe had paired up with Long-legs on the Moroccan side, while in Spain vagrant Long-legs formed pairs with Common Buzzards (for details see Elorriaga, J. & Muñoz, A-R 2013: Hybridisation between the Common Buzzard Buteo buteo buteo and the North African race of Long-legged Buzzard Buteo rufinus cirtensis in the Strait of Gibraltar:prelude or preclude to colonization? Ostrich 84: 41-45). 

Typical of a hybrid population (a hybrid swarm) like this, is that the birds are highly variable. Some look like Common Buzzards, with some features of Long-legged, while others can be almost identical to Long-leggeds save for some features clearly indicating Common Buzzard ancestry, and the rest can be anything between these two extremes. All in all, many of the birds resemble greatly the Steppe Buzzard, the eastern subspecies of Common Buzzard. 

Hybrids between different species of raptors were thought to be extremely rare in the past, but recent studies have revealed that they are in fact quite common. Hybridisation occurs also between other species of buzzards and it has been documented to take place also in harriers, falcons and spotted eagles, just to name a few. From an evolutionary aspect hybridisations like these could, at least in theory, be the start of a new species. If hybrids would interbreed only among themselves, with no genes from the original parental species being added to the population, they would with time form their own genetic entity. They would differ genetically from either of the parental species, which through hybridization would have given birth to a new, a third species.  The isolation, which is required for this to happen, rarely occurs in nature, but isolated islands could serve as such a refuge, where vagrant birds from different closely related species could hybridize and with time form a new species. Speciation through hybridization could definitely be the fast track in evolution.

Dick Forsman is a Finnish ornithologist, author, artist and travel guide. Dick's deep interest in birds, raptors in particular, started during his early childhood and ever since he has built his life around this passion. http://www.dickforsman.com.

Photos and text © Dick Forsman 

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