Eagle owl conservation project

The Eurasian eagle-owl is the largest nocturnal bird of prey in Europe and one of the most elegant, with a size similar to that of the golden eagle. Hence the choice of its name in Spanish for its distinctive features, the eagle-owl. However, its scientific name, Bubo bubo, is given because of the sound it makes at night. In his famous book "Don Quixote", Cervantes talks about the eagle-owl as the "jealous owl" with a "sad song". Envied for its spectacular orange eyes that endow it with an unparalleled night vision. Its spectacular facial expression and the beauty of its plumage make this species one of the jewels in the crown of the Iberian fauna.  

It is found across Asia and Europe. It is estimated that there are around 2,500 to 3,000 owls across Spain, except for the coast of Cantabria and the Spanish islands. However, the census calculates a lower number. Unfortunately, its mortality rate due to unnatural causes is very high, to the point that this species is listed in the "List of Wild Species in Special Protection Regimes" in Spain.

What are the causes of its high mortality rate? Can they be avoided? Collisions against urban infrastructures, predators, poisoning, and electrocution are some of the causes. To answer the second question, that is, identifying what we can do about it, is the origin of the preservation project launched by Endesa with the help of Birding Natura, wildlife conservation organisation, in collaboration with the Autonomous Government of Catalonia and MITECO.

The project is being rolled out in Catalonia (where there is an estimated population of between 550 and 700 pairs), in different parts of the region of very varied characteristics, such as the Baix Empordà, Plana de Lleida, Central Catalonia and Terres de l´Ébre. The first step involves studying the behaviour of species in as much detail as possible. To achieve this, 12 radio tracking transmitters have been attached to 12 specimens, 6 adults and 6 chicks.

The transmitter is a remote tracking device that has a GPS module and a power supply system using a battery that lasts one year. It is like a small rucksack that weighs 44 grams and is attached to the back of the bird. It only accounts for 3% of its body weight. The data is downloaded daily to a server and is also stored in the device. The information obtained will enable reports to be made that include daily activity, developments and incidents shown as charts, data tables and maps, before finally drawing the appropriate conclusions. In the case of adult specimens, it is intended to be able to discover their territorial areas, resting areas, hunting areas, places frequented both during and outside the breeding season. In the case of chicks, radio tracking will enable data to be obtained on their first flights once they leave the nest, their dispersal movements and how they establish new territorial areas.

Different criteria are used to choose the specimen. Emitters were also attached to some adult specimens, mostly by rural agents or technicians of the different natural parks, which were subsequently captured and released. On other occasions, these are specimens of other wildlife recovery centres, such as the Vallcalent Wildlife Centre or the Camadoca Wildlife Recovery Centre. In the case of chicks, the most accessible nests were chosen, in collaboration with the technicians of the Natural Parks and the Rural Agents. In all cases, the procedure is carried out without harming the animal at all, minimising discomfort, with a quick and rehearsed procedure and covering the eyes with a hood to reduce stress.

Beyond marking adults and chicks, and to complete the life cycle of the owl, the project has also monitored a nest, one of the great exclusives of this initiative since there are hardly any previous experiences with this species, so it has generated a high interest among the scientific community dedicated to the study of birds. A nest with five laying eggs was chosen when the camera was installed, of which four had already hatched. The camera was used to broadcast what happened inside the nest 24 hours a day, and more than 2,000 people, including professionals and amateurs, were able to follow, the daily development of this family that soon grew to 5 chicks via a public and free link. Thanks to the abundant food available in the area (basically rabbits), and because of something that nobody expected, the 5 chicks were born healthy, so we all managed to see something that had never been recorded before and a whole progression of their development. The conclusions and observations obtained during this pioneering activity are of high scientific value. Moreover, the chicks grew very fast and this nest became a host nest, so a sixth chick was adopted by the family, which came from a nest that had been abandoned and which was, at that time, malnourished.

The birds were tagged and the camera was removed from the nest as soon as the chicks left it. At this point, we could observe the detailed images and analyse the information to study the movements and habits of these 12 specimens, some of which, and as expected within the statistics, had to be replaced by others. The aim of this activity was to assess the elements that could be brought to help preserve these species in the first place, in the same electrical infrastructure, but also to gather enough data that can lead to proposals for improvements to be applied in other fields. All of this is aimed at making sure that the "sad song" written by Cervantes not only does not disappear but increases in all corners of our country by helping preserve the king of owls, the eagle-owl.