Jorge Molina I
Seville, (EFE).- The migration of soaring birds passing through the Strait has quadrupled since the year 2000, according to data from the Migres Program. Of the 150,000 specimens registered at that time, in 2022 it went to around 600,000, according to data from the Migres Foundation.
The monitoring program, organized by the Fundación Migres, a private non-profit scientific and cultural foundation created at the initiative of the Andalusian Regional Ministry for the Environment, has been accounting for this transit for a quarter of a century with scientifically standardized protocols.
From July 24 to October 22, registered collaborators will begin counting the passage of soaring birds this season. From two fixed observatories located in Tarifa.
For two decades the data has been recorded daily by a team of professional ornithologists. Supported by more than 1,500 volunteers and collaborators from July to October.
Storks and black kites
The Foundation’s ornithologist, Alejandro Onrubia, points to storks and black kites among the species that have increased in number. Being also the most abundant. There are also more booted, short-toed and osprey eagles, honey buzzards, Egyptian vultures, griffon vultures, marsh harriers, hawks, and black storks, he says.
“Several causes come together,” says Onrubia, “such as effective protection measures after decades of persecution. The ban on DDT and other biocides, the increase in forest area in Europe, the reduction of illegal hunting and poisons. And that global warming expands them to the north”.
According to the Foundation’s data, in the period 1999-2022 they have counted 11,962,460 soaring birds. Corresponding to 4.1 million storks and 7.8 million birds of prey. Soaring birds take advantage of rising warm air currents to gain altitude. And plan to the other continent, because they do not form in the sea.
“Counts in the Strait of Gibraltar are an excellent alternative to censuses using other methods. Achieving excellent coverage with relatively little effort”, says the president of Migres, the researcher at the Doñana Biological Station (EBD-CSIC), Miguel Ferrer.
Decrease in troops crossing the Strait
However, in this panorama of an increase in the number of soaring birds in passage, there are some exceptions, with some species that do not increase or even decrease, such as the Montagu’s harrier, he points out.
Likewise, there is a general increase in the numbers of long-distance migratory forest species, which cross the Sahara and locate their wintering grounds in the Sahel.
Others are shortening their migration, even not migrating anymore. This produces a decrease in the troops that cross the Strait, in the case of the common buzzard.
Ferrer maintains that the records of species of African affiliation, previously rare or non-existent, are rising, such as the case of the Moorish buzzard, Borní falcon, Ruppel’s vulture or the white-backed vulture. And also the records of eastern migrating species that use this western route. This is the case of the Pomeranian eagle or the papialbo harrier. EFE