The Iberian imperial eagle: a name with a history

INTRODUCTION

If we think of species unique to our country, it is inevitable to think of one of our most powerful raptors, the Iberian imperial eagle. This species is the second largest eagle in the Iberian Peninsula (surpassed only by the golden eagle) and the only raptor endemic to our country. Without a doubt, it is a symbol and icon of our biodiversity, as well as being recognized all over the world, so it is important to know the history of such a well-known name. In the past we were on the verge of losing one of our greatest jewels, fortunately it is recovering, but that's not why we should let our guard down since its confirmation status is still Endangered (according to the last Red Book of Birds of Spain published in 2021).

DISCOVERY AND FIRST DESCRIPTIONS

To start talking about the history of the Iberian imperial eagle, we must first get to know its closest relative, the eastern imperial eagle (Aquila heliaca). This species extends from Eastern Europe to much of Asia (from Russia to China), and winters in areas of East Africa, the Middle East, the Middle East and Southeast Asia. Its external resemblance (not so genetically) is such that for years the Iberian imperial eagle was considered a subspecies of it, and was therefore called Aquila heliaca adalberti until genetic studies in 1996. From this moment on, it would be permanently renamed Aquila adalberti and it was permanently separated from its relative, considering itself a species of its own. But what was the origin of this name?

Our story begins with Reinhold Brehm, a hunter and at the same time naturalist (two hobbies that used to go mostly together) who arrived in Spain in 1856 to discover our ornithological fauna. In Monte de El Pardo, the former hunting ground of the monarchy in Madrid, five specimens of imperial eagles were slaughtered between 1860 and 1861. Reinhold soon realized that he could be faced with a new discovery and sent the specimens to his father, Ludwig Brehm, one of the greatest European ornithologists of the time and an enthusiast and collector of birds who quickly saw a new species here which he called Aquila adalberti, in honor of Prince Adalbert of Bavaria, son of King Louis I of Bavaria.

This was the first time that it was doubted that our eagle was not the same species as its eastern relative, and until now it was also referred to as Aquila heliaca. Even in 1873, H. E. Dresser dedicated a section to this new species in his encyclopedia on European birds, together with the first illustrations of this species in history (made by the cartoonist J. G. Keulemans). It should not be confused that this species was dedicated to Prince Henry William Adalbert of Prussia, a mistake that has dragged on almost to this day since Dresser made this mistake in his encyclopedia.

FROM SUBSPECIES TO DEFINITIVE SPECIES

Despite Ludwig Brehm's efforts, the scientific community did not welcome the designation of the new species of the Iberian imperial eagle. It was in 1914 when Hartert and I considered our eagle a subspecies of Aquila heliaca, thus calling it A. heliaca adalberti. Other specialists defended this idea, such as Vaurie in 1965. This remained the case until finally, in 1996, molecular studies carried out by Seibold demonstrated that the Iberian imperial eagle is a totally different species from the eastern imperial eagle a million years ago. Finally, our protagonist obtains the long-awaited species name, Aquila adalberti.

It was later demonstrated, through the analysis of a mitochondrial DNA gene by Martínez-Cruz and Godoy in 2007, that both the Iberian and the Eastern species separated at the end of the Pleistocene or during the Holocene. This is a very recent period of time for the evolution of a new species (about 10000 years), which explains why their external resemblance is still so similar and has created so much controversy in the past. It is even considered that the Iberian imperial eagle itself is a species that comes directly from the eastern imperial eagle instead of both having a common ancestor, a remarkable fact since normally the species that gives rise to another one is usually extinct and is not found today.

In short, we can see throughout this history the journeys that our most incredible jewel had to go through to be considered today our only eagle endemic to the Iberian Peninsula.

BIBLIOGRAPHY

• Gonzalez, L.M. (2011). The Iberian imperial eagle: the re-emergence of a threatened species. BBVA Foundation.

• Martinez-Cruz, B., Godoy, J.A. (2007). Genetic evidence for a recent divergence and subsequent gene flow between Spanish and Eastern imperial eagles. BMC Evolutionary Biology, 7:170.

• SEO/BirdLife (López-Jiménez N. Ed). 2021. Red Book of the Birds of Spain.

• http://www.vertebradosibericos.org/aves/aquada.html