Friday, 18 April 2014

Quest for the wild Canary 9: Raptors and owls

F.tinnunculus canariensis
There is a reasonable diverse set of raptors in the islands, both residents and visitors, but there are no endemic species (at least today). There are however many endemic subspecies which are slightly different to the mainland forms found nearby in Europe and North Africa, some restricted to only a few islands and others also found on other islands in Macaronesia.
The commonest raptor we saw were two of the local races of Common Kestrel, Falco tinnunculus. On Tenerife and La Gomera we had many good views of F.t.canariensis, while on Fuerteventura we had F.t.dacotiae. The Tenerife subspecies is darker and with heavier spotting than the nominate we have in the UK, but in truth this is hard to recognise without birds to compare, and the difference in light also means they look paler than they would otherwise. The Fuerteventura form is quite pale looking as is common with desert forms. Presumably they feed largely on lizards and small birds, as the lack of diurnal rodents in the native fauna restricts their food supply. It will be interesting to see what the arrival of the Barbary Ground Squirrel on Fuerteventura will have on the resident subspecies, as they are pretty much ideal kestrel size meals.

Barbary Falcon
The other falcon we saw was a few brief views of the Barbary Falcon, F.pelegrinoides. Like their close relative the Peregrine, they are amazingly agile and fast in flight, and are presumably a major predator of the larger birds found around the island. One other falcon, Eleanora’s Falcon, breeds on the islands as a summer visitor, but it was too early in the year for them to be seen.

We had good views of a soaring Osprey, Pandion haliaetus. There are still one or two pairs nesting in the islands, but the ones usually seen are migrants passing through on their way north. With no natural well-stocked lakes, Ospreys are restricted to fishing in the sea, and I suspect that good fishing sites are probably full of bathing tourists these days.
The other common raptor seen was the Canary race of Common Buzzard, Buteo buteo insularum. Buzzards are pretty generalist in their diet, so I suspect that humans have not made much difference from their point of view – no doubt they formerly preyed on the giant lizards, but I would be very surprised if they have not switched to rabbits these days.  We also saw a single individual of the local race of Sparrowhawk, Accipiter nisus granti, which also breeds on Madeira. There are no Goshawks on the islands today, but subfossil bones have been found, suggesting they are a casualty of the deforestation following human arrival, especially after the Spanish conquest.

Egyptian Vulture
The largest raptor we were fortunate enough to see were two of the local subspecies of Egyptian Vulture, Neophron percnopterus majorensis. There are probably under 300 individuals of this subspecies left, possibly much fewer, and there is a support system being developed supplying carcases at “vulture restaurants”. There is an issue with Egyptian Vultures however – namely what did they live on before humans arrived with their livestock? With no native large mammals to supply food, and pre-human vultures would have had to survive on monk seal colonies (if any), seabird chicks, and the occasional beached whale. This seems thin pickings for a viable population, and it is quite likely that they only began breeding regularly on the islands after humans colonised them, and the differences from the mainland birds is a result of founder effects. For more on this see this paper:

Long-Eared Owl
We did not see any owls on the trip, but there are also two owl species on the islands. The more widespread is a local race of the Long-eared Owl, Asio otus canariensis. This is found on most of the islands, and these days preys heavily on rats, but also still takes its pre-human prey of birds and sometimes reptiles. Barn Owls also breed on the islands – there is a resident race Tyto alba gracilirostris on Fuerteventura and Lanzarote, but this is very rare and there are probably only a few hundred pairs on the two islands. In the past it doubtless preyed on the Lava Mouse and Dune Shearwater, along with large insects and geckos, but these days other prey items are available. The nominate race that we have in the UK is found on the western islands and may be a recent immigrant as well.

Barn Owl
Next time, I will cover the remaining non-passerines, including three very important endemics – the Laurel and Bolles pigeons, and Plain Swift

(all images from Wikipedia)

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