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Fauna -
Birds of Iberia
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Breeding on high cliff ledges in mountainous parts of southern Europe, north Africa and Asia the Griffon vulture is well represented in Iberia and like other vultures it is a scavenger feeding mostly on carcasses of dead animals which it finds by soaring over open areas sometimes in large flocks. (Although the diet of this carrion eater is almost always dead mammals we have observed a griffon vulture remove and eat a kestrel chick from it’s nest whilst the adult kestrels were away hunting).
With a length from beak to tail at around 1 metre and a wingspan of around 2.65 metres the griffon vulture is the third largest bird to be seen in the skies of Iberia. (The black vulture and bearded vulture are larger but not as numerous). The adult griffon has a whitish bald head, very broad wings and a short tail. It has a generally a dirty white neck ruff and a pale yellowish bill. Young birds have a grey bill and a pale brown ruff
Breeding starts early and often a pair can be seen flying in a synchronised glide which is believed to reinforce bonding. Nests are repaired from January onwards with egg laying in February/March and chicks around April. Incubation is shared and the egg is never left unattended. When one bird returns from feeding a swap over takes place and the incubating bird leaves the nest in search of its own food. Before settling down the parent tidies the nest site and turns the egg very gently. Griffons are excellent parents and will mate for life, also using the same nest site each year if they can. Once the chick has hatched it is guarded by one of the parents until it is big enough to not become a food supply for a passing Egyptian vulture, raven or other opportunistic scavenging bird.
The young are ready to fledge at 3 to 4 months after hatching and the most critical time seems to be whilst learning to fly following fledging. Although they will join the adults at a feeding site and attempt to feed they still rely on their parents to support them for anything up to 90 days more. A griffon vulture will be mature enough to breed at between 4 and 7 years and their lifespan can be as long as 40 years.
Griffons are very social birds and prefer living and nesting in colonies. Very often more than 100 pairs compose a colony and there are some huge colonies in Iberia numbering possibly a thousand birds. Estimates as to the Iberian population range between 18 and 22 thousand individuals at any one time.
The hierarchy of a griffon vulture colony can be likened to the pecking order of a flock of chickens on a farmyard. There are alpha individuals and families that have the best choice of roosting and nesting positions. They also have priority at feeding sites. Even if lower ranking griffons are already present, when the colony alphas arrive a small squabble will ensue almost always resulting in the alphas getting the best pickings. When observing the birds returning to their nesting sites after feeding it is possible to see extended family groups landing in the same area that they control and defend from other birds. We have observed what seemed to be a juvenile bird of a previous year aiding in the feeding of a current chick. (One adult bird on the nest with chick and two more returning and individually feeding the same chick). This behaviour still needs to be confirmed as being widespread.
Although there are many griffons in Iberia at the moment their numbers have been radically reduced across their European range by poisoning, shooting and habitat loss coupled with new laws on the disposal of dead farm animals. The population in Iberia has been supported in the past by a huge inefficiency in farming practises whereby anything up to 50 percent of bred farm animals (mostly sheep, cows and pigs) die before reaching slaughtering age. Traditionally the farmer has dumped the carcasses in a field in order for the vultures to clean up.
However, with new European laws it was made illegal to dump dead livestock in the countryside so a falsely supported population of griffon vultures (and other scavenging animals) suddenly had a much smaller supply of available food. (wild stocks of food just don't exist to support this many vultures)
To combat this shortfall some regions of Iberia set up feeding stations called "muladeros" and placed carcasses of horses and donkeys (No cows because of BSE). Later some of these feeding stations were closed forcing the griffons to fly further in the hunt for food. To the hungry vulture sheep in the process of lambing and animals in the process of dying also became necessary to their survival.
With irresponsible and ill researched headline grabbing articles in the Iberian press like "killer vultures ate my sheep" vultures, once again have taken a step backward in peoples minds and imagination.
Some feeding stations have re-opened and the EU is looking at ways of introducing new laws to allow farmers once again to place thier dead livesock in the fields for the vultures and other carrion eaters.
Iberia is the last stronghold of this amazing species of raptor and great care needs to be taken in the future if we are not to lose it like we have lost so many other species so important to the natural fabric of Iberia.
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Last Updated on Tuesday, 14 July 2009 14:05 |
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