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Environmental Management

The Mediterranean eagle’s uncertain future

JORDI MONTANER | JANUARY 24th, 2011

In Catalonia, human activity accounts for three times the number of eagle deaths than natural causes. Half of these deaths are due to impacts or electrocution with electric towers. A team from the University of Barcelona is working to find solutions

The conservation of Mediterranean landscape is not just a cosmetic issue. It is also key to continuing to enjoy a species as iconic as Bonelli's eagle (Aquila fasciata), an agile and powerful predator that is threatened throughout Europe.

But to ensure the conservation of the landscape is no easy task. Joan Real, director of the Bonelli's Eagle Conservation team at the University of Barcelona (UB), regrets that the most emblematic species of the Mediterranean habitats are increasingly threatened. "These are species that no one would believe are in danger, such as rabbits, hares, quail, lizards, some arthropods..." And, of course, Bonelli's eagle.

These are animals that for centuries have been common in open areas of grass, shrubs and small cropland; species that the forestation of the Catalan landscape has left without a habitat. "This must be said carefully to avoid misunderstandings, but forest fires also favor some species that are typical of these ecosystems", Real said, referring to the fact that open areas created by naturally occurring fires are favorable for these Mediterranean species.

Transformed ecosystems

The favorite prey of Bonelli's eagle are rabbits. But Real explained that the rabbit’s decline due to habitat changes and viral diseases has led the eagles to change their diet and catch squirrels, doves, pigeons, thrushes, and even crows or seagulls“.These new hunting habits are an indicator of the ecosystem increasingly being transformed and humanized, and they cause, among other things, the eagles to have more difficulties in finding food and, in turn, that their hunting areas are placed in human areas with dangers to their survival”.

The problem of electrical towers

The UB team has been studying Bonelli’s eagles since the 1980's. This makes their observations a global reference in terms of the conservation of this predator. Real said that the eagles’ population has fallen almost 30% during this time period and even today in Catalonia three times the number of eagles die from human causes than natural ones.

Half of these deaths are due to impacts or electrocution with electric towers. "It is paradoxical that Catalonia’s eagles, which are among the most studied, are also the most threatened with extinction", said Real, who began their study in the Natural Park of Sant Llorenç de Munt. "Fortunately, this park has achieved for the first time a significant reduction in eagle mortality thanks to a partnership of utility companies, government authorities and researchers. We have determined what characteristics make certain electrical towers more dangerous for birds and now we have a very powerful tool to implement in conservation measures”.

Electrocution from power lines could be minimized and corrected with proper planning Real insisted that both electrocutions and collisions with power lines could be minimized and corrected with proper planning, either by correcting the existing lines, those which researchers have predicted as the most dangerous -probably only 5-10% of the existing lines- along with future ones.

For 30 years, Real’s team has been analyzing the impact of the electrical towers in the biology of the Bonelli's eagle. It has done so following a score of specimens with radio-frequency devices. This has allowed them to document one of the least known types of accidents for birds, the collision with power lines, which occurs in mid-flight and affects many endangered species. They have seen that the risk of impact is especially dangerous for power lines with many cables and more frequent in areas of scrubland than in forested areas. This has led the team to make risk estimates for sections of power lines and to optimize resources to correct this type of accident. The towers are a danger not only for eagles but also for other birds. Eighteen percent of the deaths of bearded vultures (Gypaetus barbatus) in Europe, for example, are caused by impacts with electrical towers.

The example of France

"Catalonia presently has about 65 pairs, accounting for 7-8% of the European population of Bonelli’s eagle. In Andalusia, however, the population reaches 300 pairs (Spain, as a whole, accounts for 80% of Bonelli's eagles in Europe). In France, these eagles had a difficult time at the end of the last century and the authorities have taken their conservation seriously; it should be an example to follow”, Real said.

THE PATRONAGE OF MIQUEL TORRES
Joan Real stressed that all the work of the UB team has been made possible by the Miquel Torres Foundation in Vilafranca del Penedès, "which for a long time has been sponsoring our team’s work and is a clear example of how private industry can intervene positively in the work of scientific research and conservation. " The biologist makes it clear that all the efforts, publications and experience gained during these 30 years would have been impossible without the support of the Foundation.

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