Yellow-legged Gull, or Larus michahellis in Latin, is a well-known bird in all parts of the Adriatic and the Mediterranean so a description is really not needed.
The species breeds in Croatia. It nests on cliffs and islets along the Adriatic and the Kornati are not an exception.
In order to research the taxonomic affiliation of our yellow-legged gulls as well as their relationship with other gulls in the Mediterranean, Atlantic and North Sea, we have monitor their movements. In order to monitor their movements, the birds have to be marked harmlessly, and that's done with special bird rings. Not everybody can put things on wild birds. To do that, you have to be trained bird ringer with a licence from the Croatian Institute for Ornithology.
More than a thousand young gulls were ringed in the Kornati National Park during the last ten years: a young bird is ringed with a small aluminium ring and a small plastic (yellow) one, engraved with a unique number. We can distinguish them in that way, and the gulls become birds with their own past and future that we can monitor.
The procedure, deceptively simple, is the foundation of scientific ringing of millions of wild birds throughout the world.
Immediately after ringing, all birds are released unharmed in the location where they were caught. Every sighting of a ringed bird (we call that a "finding") – either a sighting at distance, the bird being caught again and released, or finding the bird dead – tells us something about its life, particularly about its movements. A finding can supply data about bird mortality and age, data about habitats and sites where birds stay... In other words, parameters that can help distinguish different populations, recognise causes of changes in the population size, plan bird conservation, and so on.
Thanks to ringing and bird watchers from other European countries, the Kornati NP has gathered a lot of data about its ringed gulls that were found in the interior of Croatia, Italy, Austria, Hungary, Romania, Serbia, and even in the north of Germany and Poland.
The yellow-legged gull ringed on the island of Mrtovnjak holds the current record: it was found in the north of Poland, in Gdańsk, 1200-1300 kilometres away from the place of ringing. The latest news about another young gull (ringed on Purara) were that it was seen and photographed in Romania, at a fishpond near Rotbav, 800 kilometres from the Kornati. This was the first finding of "our" gull in Romania.