The number of white storks nesting in Portugal has increased fivefold in the past two decades, with the previously endangered birds making a comeback partly due to a more plentiful supply of their favourite seafood and partly due to improved nesting conditions, Portuguese Society for the Study of Birds (SPEA) said on Monday.
According to a census published by the society, the number of stork nests — a familiar sight as they are often perched atop of buildings and on electricity pylons — recorded in the country rose to at least 7,685 last year.
That was a more than fivefold increase from 1984, when the bird was considered to be at risk of disappearing altogether.
The number of storks in the country is now at the same level as during the first half of the 20th century before widespread pesticide use and the loss of their habitats due to the drainage of wetlands led their numbers to decline, the SPEA said.
Efforts by power companies to make electrical pylons safer for nests and better feeding opportunities are behind the rise in numbers, the society said.
Goncalo Rosa, a scientist with the conservation group who coordinated the nest count, said the introduction of Louisiana crayfish, which reproduce quickly, to Portuguese wetlands in 1979 had given the storks an abundant new food source.
“This is the main factor leading to the recovery of the white stork population in Portugal,” he told AFP, adding stork numbers have risen in neighbouring Spain and France for the same reason.
The abundance of crayfish, combined with food provided by trash dumps, has also led growing numbers of white storks to stay in southern Portugal year-round instead of making their annual migration to wintering grounds in Africa.
More than 4,000 storks, mostly of reproductive age, now spend their winters in Portugal where they forage in freshly-plowed fields, lowland wet pastures and marshes, avoiding the mortality associated with migration, said Rosa.
The long-necked birds are also facing less danger of electrocution, as over the past two decades power firm EDP-Energias de Portugal and power grid operator REN have worked to make their pylons more stork-friendly, the SPEA said.
In some cases maintenance workers from the two firms will move a stork nest, which can be over two metres (6.6 feet) in diameter, to a safer location.
Just over 37 percent of all stork nests found in Portugal last year were perched on electricity pylons, Rosa said.
The risks that such nesting places pose — and not only to the birds themselves — was made clear in May 2000, when a stork’s nest became tangled in power lines, plunging Lisbon and the southern half of Portugal into darkness in the nation’s most extensive blackout in two decades.
The end of a long-lasting and severe drought in the sub-Saharan Sahel region of Africa where most Portuguese storks spend their winters has also played a role in the increase in their numbers, said Rosa.
The census of white stork nests was carried out across Portugal throughout 2004 in cooperation with the environment ministry and involved some 500 bird-watchers.
