The Iberian Imperial Eagle in flight may sometimes be confused with other birds of prey. The careful observation of the silhouette is very important for a correct identification.
1) Iberian Imperial Eagle (Aquila adalberti)
Very large eagle, characterized by its long and uniformly broad wings, and relatively short tail. Massive head and beak, more imposing than in the Golden Eagle. It soars with its wings straight, only occasionally with the tips of the wings slightly upturned.
2) Golden Eagle (Aquila chrysaetos)
This is largest eagle of the Iberian Peninsula and is characterized by its long wings, narrower at the base and inner part of the “hand” (and not straight like those of the Iberian Imperial Eagle), and by their long tail (longer than the tail of the Iberian Imperial Eagle), which gives it a somewhat different silhouette from the Iberian Imperial Eagle. It glides with the wings slightly upturned forming a V.
3) Bonelli’s Eagle (Aquila fasciata)
Medium-large eagle, characterized by broad wings, broader in the centre, and straight tail, long and square. It glides with straight wings and generally the “fingers” are less evident than in the two species of larger build.
4) Cinereous Vulture (Aegypius monachus)
It is the largest bird of prey in Europe and is characterized by long and uniformly broad wings (broader than in eagles), long “fingers” and short head and tail. It glides with its wings slightly arched downwards.
5) Griffon Vulture (Gyps fulvus)
Large vulture, characterized by very long and very broad wings, with the “arm” broader than the “hand”, and a short and rounded tail. It glides with its wings slightly upturned, forming a V.
6) Egyptian Vulture (Neophron percnopterus)
Medium-large vulture, characterized by its short head with a straight and long beak, broad wings with prominent “fingers” and a long wedge-shaped tail. It glides with its wings straight.
The plumage of the Iberian Imperial Eagle goes through six different phases until it reaches the final adult color.
In the first months of life, the "Juvenile" have a reddish coloration, in rusty tones.
The plumage then becomes worn out and discoloured due to the sun and the physical abrasion, becoming yellowish/golden, similar to the colour of the straw, whereby the term "Straw coloured" is used to describe this phase. The more advanced "Straw coloured" gradually begin to replace the feathers of the body, head, neck and wing covers with new feathers, of orange tone, with distinct tonalities being observed in the lighter areas of these birds.
Later, they begin to acquire new feathers, dark brown, which stand out from the pale yellow background, giving the birds a checkered appearance, being therefore used the term "Chess". When they still have less than 50% of dark feathers, the plumage is called “Pale chess”. In this phase some flight feathers (remiges) are already being changed, as well as some rectrices.
When the plumage has more than 50% dark feathers, it is called “Dark chess”. In this plumage adult feathers can sometimes already be seen in the central zone of the tail.
The "Subadult" (or "imperfect adult") is characterized by a dark-brown, virtually black plumage, very similar to adults, although still with some lighter remnants of the previous plumage remain; white shoulders are already visible. The tail shows the adult pattern, being grey with a broad black terminal band.
The definitive "Adult" plumage is virtually black, with golden feathers in the posterior part of the head and neck. A white border, of variable size, delimits the wings from the shoulders and/or scapular region. The base of the tail is light gray with a broad black terminal band. The characteristic white border of this species presents a unique shape in each bird, invariable over time, allowing the individual identification of each specimen. In rare cases, this board may not occur.
