Iberian imperial eagle: steppe?

Until the beginning of the Quaternary period, a species of eagle dominated the steppes of present-day Europe. With the arrival of glaciations, this species, like so many others, was pushed to the south. The Iberian Peninsula functions during glaciations as a “cul de sac” and this, together with the orientation of our complex orography, has generated a biodiversity hotspot of global relevance.

The Iberian Peninsula was a refuge for the steppe eagle for tens of thousands of years, thanks to the availability of rabbits. When the glaciation receded, it left space for the eagles, but by then it was too late. Iberian populations had adapted to eating rabbits. As the rabbit did not expand significantly beyond the peninsula, the steppe eagle was trapped. It was far removed from the rest of the Eastern Imperial Eagle populations, a new species had been born. Now it was the Iberian imperial eagle, which we were talking about hither.

We grew up seeing the Iberian imperial eagle in formidable oak forests in the Mediterranean mountains. And in Doñana. Félix Rodríguez de la Fuente modeled the imaginary and concepts of several generations of naturalists, biologists and nature lovers. We grew up imagining the imperial mountains in the mountains of Toledo or Monfragüe.

The reality is that those eagles were there, because they were such hidden places that going to kill them was very difficult. And that's why they survived the brutal persecution that raptors in general and great eagles in particular suffered well into the 80s of the 20th century.

At present, this problem is generally of little importance. In addition, the wild rabbit has recovered in much of the peninsula. Steppe eagle genes have once again taken Iberian imperial eagles to the same habitats occupied by the eastern imperial eagle, flat areas, with prey available and with large trees for nesting. And it needs little else, sometimes not even that.

The population in 2022 was 841 couples, in 2017 it was 536. In 5 years, it has increased by 56.9%. The increase is 11.4% per year. If there are no changes in the evolution of the population in 2026 there will be about 1,300 couples. And then it will have exceeded the threshold of 2,500 adult specimens, a criterion that the IUCN allows it to be classified in the category of Endangered. Will we see that milestone so soon?

Well, to a large extent it depends on how the rabbit is doing. If there are no outbreaks of new variants of the diseases you suffer from or some other new disease, you will usually reach that number. It's normal to find couples who take out 3 and 4 chickens. In addition, it is normal for couples to consist of subadults and even juveniles, the breeding population is young and many couples formed in recent years will increase their productivity, as they gain experience.

But what about unnatural mortality factors? The traditional ones will continue to decline, less poison, fewer shootings of specimens, fewer destroyed nests and fewer dangerous lines. Except for one. Mortality with wind turbines.

This factor is going to increase. It will affect young specimens. They will not be authorized in areas with imperial eagles. But young people in their dispersion phases will find more wind turbines every year. Mortality against wind turbines will probably not reach the mortality caused by electrocution in power lines. And we also have solutions.

All wind turbines must have detection, deterrence and shutdown devices. This will benefit the imperials, but also the rest of the birds of prey and birds over one meter in wingspan.

The effect of controlling rabbit populations in at least 1 km around wind turbines must be assessed. Reducing rabbit density will partly prevent the risk of raptors in general using the environment of wind farms. There should be no abundant rabbit populations in the environment of wind turbines, the density must be such that it is not an attractant. In addition, the supply of carrion from both livestock and big game must be eliminated. And consequently, improve rabbit management in places where there are no wind turbines to reverse the potential loss of resources for raptors.

The behavior of adults in front of wind turbines must be studied. We need to know the rejection distances, if any, and how they interact with wind turbines as well as the variables that govern behavior in the face of these new infrastructures, wind? landscape? human activity?.

The development of wind energy, with ever larger machines, presents us with challenges that we cannot ignore. Decisions must be made, based on scientific criteria, listening to all parties, sponsors, scientists, associations and consultants. But these criteria must consider that the development of wind energy is essential for the decarbonization of energy. And that will cost us the loss of imperials and other birds and chiroptera by collision. That's for sure.

It is essential that conservation areas be defined, beyond RN2000, that allow us to maintain areas that house enough imperial pairs to ensure that sufficient productivity is maintained to conserve this species. Because the development in the coming years of many new wind farms is certain.

References:

The Iberian imperial eagle is recovering: it has 841 breeding pairs in the Iberian Peninsula (miteco.gob.es)

Aquila adalberti (Spanish Imperial Eagle) (iucnredlist.org)