Griffon Vulture – an identity card
The feathers change their colour over the years. One-year-old birds are dark brown, their beaks are black, and the collar feathers are dark brown, long, swaying and arrow-shaped. The head and neck are covered with short white feathers, quite different from that of the adult birds. Feathers change constantly and this change continues for a few years. When they are five and they reach sexual maturity their colour is brown-yellow, except for the wings and the tail, which are black. Vultures get the colour of an adult bird when they are seven. Their beak is yellow and the collar is white with paper-like feather. The feet of young birds are yellow with brown spots, whereas the feet of adult birds are gray to blue-gray, with black claws. In the third year the colour of their eyes changes and their irises change from dark grey, almost black to light-brown, typical for adult birds. After that they gradually change to orange in 10–20-year-old birds and later on to yellow in birds older than 25 years.
Interesting fact: Griffon vultures live in colonies. The number of nests in one colony is from 5 to more than 100 pairs, but it is usually about 15–20 pairs. In Croatia they nest at an altitude of 10 m, whereas in Spain at the height of up to 1,800 m. In the Caucasus they have been observed nesting at an altitude of up to 2,750 m.
Nest building begins up to two months before the actual laying of eggs. At the beginning both parents are gathering material for building the nest, but at a later stage the male spends more time collecting the material, whereas the female is building the nest. Nests are built from twigs and turf. Their size depends on the size of the nest shelf on the cliff, but they usually have a diameter of 60–100 cm and are 20–30 cm high. During the reproductive season, birds begin with landing on the nest, maintaining their wings spread, to await the arrival of the partner. Usually the bird lands on the nest, while holding the building material in its beak, waving its wings and then dropping the material. The partner approaches, spreads its wings, and after that they stand besides one another for a while or they make circles above the nesting place with their dorsal feathers raised, signalising the arousal. After that they can start building the nest or they begin the copulation. The copulation is performed on the nest or next to it.
Interesting fact: The eggs are elliptical or oval, sometimes slightly extended. They are usually white and their dimension is typically 92x70 mm. During the incubation, both parents are nesting. They exchange once or twice a day. The offspring hatches after 48–55 days, with their eyes open and they are completely covered with feathers. They remain in the nest for almost four months (110–115 days), when they are 80–90 days old they can leave the nest and fly at shorter distances.
The female vulture lays one egg a year. The survival rate of a young bird by the time it leaves the nest is just above 50%, so we can say that one female brings a young griffon vulture to the world only every second year.
Now days griffon vultures live in Croatia only on the islands of Kvarner: on Cres, Krk, Prvić, Plavnik and occasionally on Pag. In those few colonies there live approx. 130 breeding pairs. The colonies on the islands Cres, Krk and Prvić are protected by law as ornithological reserves. The ornithological reserve on the island Krk is the oldest one and is even the first ornithological reserve in the whole world. It was established exclusively for the protection of the griffon vulture. By decision of the municipality of Krk of 30th December 1969, a part of the island Krk from cape Glavina to Mala luka bay and 1-km-wide coast were declared to be a special ornithological reserve. The island Prvić was declared a reserve in 1972 and in 1986 two other ornithological reserves were established on the island Cres.