Saturday, 17 December 2016

Spain 4: Vultures

Griffon Vulture, Pyrenees
Raptors are always a draw for birders and the biggest of all are the vultures. This trip I had good views of two species – Eurasian Griffon Vulture Gyps fulvus which I have seen before, and a lifer for me, the Lammergeier or Bearded Vulture Gypaetus barbatus. Spain has two other species, Cinereous Vulture (the largest species – it has a wingspan as great as a California Condor) and the Egyptian Vulture (the smallest vulture in Europe).

Spain has a very healthy population of Griffon Vultures, with perhaps 25,000 pairs. The main problems they face is changes in agricultural practise. In the past dead livestock would be left in the fields to be cleared up rapidly by the vultures, but EU rules requiring incineration of dead animals deprived them of food. Vulture feeding areas have been set up in many areas which attracts them and many other scavengers, and it was at one of these that we got good views of both Griffon and Lammergeier. The other main threat, one also faced by many other raptors, is accidental poisoning as a result of eating poisoned bait set out for foxes and other agricultural pests.
Griffon and Cinereous Vultures at a dead sheep, Portugal
Griffons are unusual for raptors in being colonial and quite social birds. They are also very long lived, with captive birds living to over 50 years. The rapid congregation of vultures at a carcass is a result of their exploitation of social networks when searching for food. A soaring vulture not only scans the ground but also keeps a close eye on other vultures spaced out over the ground. As soon as one finds a carcass all others in visual range see it descend and hurry to join the feast. Within perhaps an hour of the first location a crowd of dozens will congregate to compete. At a carcass there is a hierarchy of access, with Cinereous vultures dominant to Griffons and Egyptians waiting until last, followed by Ravens and smaller corvids.

When only bones are left the final member of the clean up crew arrives. The Lammergeier is one of the most specialised of all birds, with a diet consisting almost entirely of bones, or rather bone marrow. Lacking the bone cracking jaws of hyenas, instead they fly high with a large bone and drop it onto rocks, thus breaking them open to access the rich marrow. Smaller bones will be swallowed whole, to be dissolved by the powerful stomach acids. This is so effective that it renders the whole EU “hygienic” regulations frankly pointless – a vulture stomach is as good as an incinerator for destroying animal waste and requires no fossil fuels after all.
Unfortunately, the specialised nature of the Lammergeir’s ecology means they are more particular in their habitat than Griffons. They are almost entirely mountain birds, rarely seen below 1000m, and have a vast range centred on the Himalayas, with smaller populations in southern Europe and Ethiopia. Aside from mountains, they do best in areas with a healthy population of predators to supply the bones they need. At altitude especially bones desiccate, but are still usable by the birds for months after the prey is picked clean by other birds. They will also take some live prey, especially tortoises, which they kill in the same way as they break open bones.

We were fortunate to see an adult pair of Lammergeier mating at the feeding station. I presume because of their diet, they have access to food almost equally all year round, and the breeding season starts in November in Europe. Lammergeier nests can be huge, with old nests over 2m across and 1m deep, with 1 or 2 eggs laid. Once fledged, young may remain with the parents for over a year before dispersing, so successful pairs breed only every other year. As with Griffons, they are long lived, with captives living to over 40. Young Lammergeier often disperse widely away from the initial release point. How far was shown this year, where unbelievably a juvenile actually showed up near Bristol, on the other side of the River Severn in Wales. As far as I know it has not been seen since. And I hope it has made its way back to the continent. The UK is not natural vulture habitat – the lack of high mountains and warm dry countryside to generate thermals for soaring means that smaller scavengers such as Red Kite, Raven, and White-Tailed Eagle were the traditional avian clean up crew.

The population of Lammergeier in Spain is much smaller than for Griffons, and most birds are in the Pyrennees. There is an introduction project underway in Andalucia in southern Spain, and also in other parts of Europe. Reintroduction projects for vultures have often been very successful, probably because they take easily to supplemental feeding stations, so this is one of the few good prospects for the well-known disastrous situation in India, where there has been a mass die-off of vultures as a result of livestock being treated with antibiotics toxic to them.

(Lammergeier image from Wikipedia, rest are mine)

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