IMPERIAL EAGLES | 𝘈𝘲𝘶𝘪𝘭𝘢 𝘢𝘥𝘢𝘭𝘣𝘦𝘳𝘵𝘪, 𝘈𝘲𝘶𝘪𝘭𝘢 𝘩𝘦𝘭𝘪𝘢𝘤𝘢

ALMOST TWINS

Observing these two eagles in the same location in nature, unless it’s a zoo, is practically impossible. But in today’s illustration, we’ll play with biogeography to learn more about these two extraordinary raptors.

To an untrained eye, the Spanish Imperial Eagle (Aquila adalberti) on the left and the Eastern Imperial Eagle (Aquila heliaca) on the right may appear almost identical.

And it’s true, they are two very similar raptors, and apart from a different distribution of white wing feathers (with the Spanish eagle having more extensive white feathers on the lesser, median, and greater coverts, while the Eastern eagle having more extensive white feathers on the scapulars) and some differences in size and proportions, the two eagles would seem “almost twins.”

In reality, they are two different species, geographically separated by thousands of kilometers. The Spanish imperial eagle only lives in Spain and a small part of Portugal. The Eastern imperial eagle, on the other hand, inhabits a territory ranging from Hungary and Korea to Siberia and Kenya. The Eastern eagle is mostly a medium-range migratory bird, while the Spanish eagle is sedentary.

Why are these two eagles, once considered the same species, now separated by thousands of kilometers? The answer could lie in the Ice Age, or rather, its end.

The Spanish Imperial Eagle might have initially been a relic population of the Eastern Imperial Eagle, which, due to habitat changes following the end of the Ice Age, became isolated in the Iberian Peninsula, giving rise to a separate and isolated species, developing differences in morphology, ecology, and genetics.