To clear the ground, we must first explain that the young of the Imperial Eagle are, in their first plumage, of a uniform, rich tawny chestnut, or café-au-lait colour. We have shot beautiful examples in this stage in June and July, when, during the intense mid-day heat, the young eagles are wont to seek the shade of the tree whereon they were hatched. This plumage continues during two or three years—or more: but the original brightness and depth of hue is rapidly lost with age and exposure to the southern sun. In a few months, these young eagles have faded to an almost colourless, "washed-out" shade that appears almost white at a distance.[41]
Their next stage is to acquire the dark plumage of maturity—a metamorphosis which probably extends over several years. The black feathers growing gradually and irregularly among the light ones, give the bird, during this period, a peculiar piebald or spotted appearance—(see photo below). It is also worth adding, as a curious fact, that many of the feathers of the wing-coverts, scapulars, &c., show light on one side of the shaft, and dark on the other. During all this protracted adolescence, it has usually been considered that these eagles did not breed.
During the winter months in Andalucia one sees many of these tawny-coloured eagles, the majority pale in hue—"washed-out" as Griffon Vultures—(undoubtedly young Imperials)—but there are others, less numerous, of a rich bright chestnut, and some of these, we think, may belong to a different species.
In April, 1883, the writer found a nest of one of these large tawny eagles in the distant Corral de la Cita. It was placed on the summit of a stone-pine, almost covering the broad, bushy top, and we had an excellent view of the old bird, as she rose from the nest about 100 yards away:—de las coloradas, == "one of the tawny kind!" as my companion remarked. The place was remote, and night too near to allow of our then awaiting her return (though we should have done so at any cost), so, after taking the two eggs (large dusky white, quite spotless), substituting for them a couple of hard-boiled hen's eggs, and setting a circular steel-trap in the nest, we left it. On returning next morning there was no sign of the eagle at the nest. After walking all round, shouting out, and going up an adjacent sand-ridge which all but overlooked it, we were satisfied she was not there, especially as the night before she had risen rather wild. Accordingly we prepared to ascend; but whilst throwing the rope over the lowest branches, a great shadow suddenly glided across the sand beside me, and on looking up, there was the great chestnut-coloured eagle slowly flapping from her nest within fifteen or twenty yards overhead. Before I could drop the rope and run to my gun, the chance was gone; unluckily, however, the shot took some effect, and though it failed to stop the eagle, she went away badly struck, with one leg hanging down, and never returned. Thus, by bad luck, an opportunity of settling a doubtful point was thrown away.
In June of the same year (1883), we obtained a tawny eagle, which we then imagined would be a young Imperial of the year, and being only winged, the bird was placed in the garden at Jerez, where it lived till the autumn of 1885. It was then (at any rate) two and a half years old, and possibly much older, yet it had never changed colour at all. The whole plumage was rich tawny chestnut, rather lighter beneath, and the new autumn feathers, which were growing at the time of the bird's death, were also coming bright chestnut, and without a sign of black. This eagle, which we now have set-up, has also, to our eye, quite a different physical type to A. adalberti, old or young, being heavier and more massive in build, beak, and claws—indeed, almost vulturine (see photo above). The middle toe appears to have four scutellæ, against six (one rudimentary) in A. adalberti; tail above uniform dark brown. In captivity it was much noisier, and more nonchalant, than the Imperial.
As already mentioned, we have observed these rich-coloured tawny eagles on many occasions during the winter months. The forest-guards distinguish them from the young Imperial Eagles, saying they were most numerous in winter. Casual observation is not, of course, of much value on fine points, and we give their opinion for what it may be worth. The late Crown Prince Rudolph of Austria also appears to have found a tawny eagle nesting in Andalucia ("Sport and Ornithology," p. 491), but did not secure the birds.
It seems probable that a large tawny-coloured eagle—whether the African A. rapax, or otherwise—does breed in Southern Spain, though sporadically both as to time and place, the wooded districts around Córdova being the most likely locality.