for National Geographic News
Somewhere in the reedy wetlands of easternmost England, Britain's tallest and perhaps rarest resident bird is making itself at home, more than four centuries after being forced into exile.
But the exact location of the Eurasian, or common, crane (Grus grus) isn't a question those watching over the bird care to answer just yetthey'll wait until they feel the bird's future is secure.
The cranes first returned to eastern England in the early 1980s. The few ornithologists who knew about the birds' arrival didn't consider it a major event at the time, since cranes from continental Europe are occasionally blown astray during spring and fall migrations. But these particular cranes never went away.
In subsequent years the number of resident cranes has crept up to between 15 and 20. Experts believe there are currently three to four breeding pairs, representing the U.K.'s first resident colony since the 16th century.
"They are in an area of marshland that's fairly typical for the species," said Malcolm Ogilvie, secretary of the Rare Breeding Birds Panel of the U.K. "A single pair first tried to breed in 1981. Since then they have bred intermittently. But they are not that successful."
The colony has shown an extremely slow growth rateless than a bird per year on average. Female cranes lay a maximum of two eggs each year. Egg predation, among other factors, may be holding the birds back, according to Ogilvie. He notes that the exact cause of their slow population growth is difficult to identify, since the cranes spend most of their time on private land that is largely off-limits to researchers.
"There's no knowledge as to what turnover there's been or whether any of the young ones have returned and bred in their own right. All that's really known is how many attempt to breed and whether they produce any young," Ogilivie said. "The landowner has been very protective of the birds all this time and has not allowed detailed study. This is understandable, because otherwise you risk disturbing [the birds]."
Ogilivie believes access restrictions imposed by the landowner is a likely reason why the cranes have stayed.
The secret site lies somewhere in the Norfolk Broads, a landscape of rivers, fens, grazing marshes, and waterlogged woodlands near the North Sea.
Britain's largest protected wetland, the Norfolk Broads takes its name from the network of shallow lakes, or broads, dug in the Middle Ages as a source of peat for fuel. The entire region covers some 30,000 hectares (74,000 acres) and extends south into the neighboring county of Suffolk.
The unheralded and unaided return of the charismatic cranes stands in marked contrast to the successful reintroduction of other species to the U.K. In recent years fanfare accompanied the return of species like the osprey and red kite in England and the white-tailed eagle in Scotland.
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