ageing Booted Eagles is pretty easy when seen well but the darker birds can invite confusion with a few other raptor species namely, Honey Buzzard juvs, Black Kite and Bonelli's Eagle -- one of the two commonest raptors we saw with several over 1400 logged in the 8 days and a peak of 670 on the big day of the 22nd -- proportions of dark to light birds varied daily with a seeming increase in dark birds later in the week when there were 50/50 on some days
Dick Forsman's new book Flight Identification of Raptors of Europe, North Africa and the Middle East is the go to book for raptor ID and ageing etc
Two juvenile pale morph birds above
a pale adult -- adults tend to be more heavily marked and duller in the white areas and have less even trailing edges to the flight feathers
a much paler and less well marked adult above but still lacking the obvious pale trailing edge tp the flight feathers and with irregular shape to the rear wing
an adult with some wing damage - such birds were not common but not rare -- raptors seem to suffer everywhere even in supposedly civilised western Europe particularly Britain
above and below dark morph juveniles of the more rufous phase formerly called intermediate juvs - note uniform pale trailing edge to wing and tail and pristine plumage
More rufous toned dark morph juveniles
above a very pale juvenile pale morph bird with almost no markings on the breast and underwing coverts but the typical rusty brown toned head and lower neck
the so called headlights, white marks on the inner upperwing coverts are a remarkably obvious feature even on dark birds on which the upperpart pattern is less well marked than in pale birds
another very clean pale morph juvenile above and below part of the upper wing showing the neat pale fringes to the coverts and flight feathers indicating a juvenile
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