Spanish Imperial Eagle – Variation in juveniles and immatures

Spanish Imperial Eagle (Aquila adalberti). Valladolid, June 2011. Photographer: Juan Sagardía
A young adult female Spanish Imperial Eagle. A stunning bird, for sure, particularly if seen this well! Adults are relatively straightforward to Identify, but some juveniles, and especially immature birds, can be very difficult to tell apart from Easterns.

By Dani López-Velasco

I was recently asked about an interesting looking immature (presumably a 4cy) Imperial Eagle sp. seen in Sweden, and I thought it was about time to share some photos, and comments, on variation within juvenile and immature Spanish Imperial Eagles (Aquila adalberti).

First, a photo of the Swedish bird, taken by Lasse Olsson, from the Surfbirds gallery.

Imperial Eagle sp, probably 4cy Eastern. Sweden, July 2012. Photographer: Lasse Olsson. Photo taken from Surfbirds gallery

I am, by no means, an expert on the 2 Imperial Eagles, although I have seen quite a few Easterns, mainly in Oman, and of course plenty of Spanish over here in Spain (mainly adults and juveniles of the latter though; it’s not easy at all to see immature birds, as they wander around a lot).

But I will try to offer some visual information on variation and ID pitfalls of juvenile and immature Spanish Imperial Eagles, which can perhaps be useful for future records.

I´m not completely sure of the ID of the swedish bird. It is most likely an Eastern, typically lacking any warm rufous colouration on the immature-type underparts and underwing coverts. However, based on my experience, it might be difficult to rule out with certainty a Spanish. Some of them can be scarily similar. See for yourself after checking some of the photos below…

Most fresh juveniles, and full-grown adult SIE, are relatively easy to identify. However, some juveniles can be more difficult than what has been published. They can be quite similar to some Easterns, and, above all,  worn birds can be extremely similar to pale belisarius Tawny Eagles (Aquila rapax), and also to fulvescens Greater Spotted Eagles (Aquila clanga).

Many, if not all, of the recent Tawny Eagle records from Morocco refer, in fact, to wandering juvenile Spanish Imperial Eagles!

Separating immature (mainly 3-5cy) Spanish from Eastern, before the first obvious and diagnostic white feathers on the leading edge of the wing start to appear, usually by late 4cy-5cy,  can be very difficult, or even impossible in some cases.  Especially on birds lacking warm rufous immature-type feathers on the head, underparts and underwing coverts. And these birds exist. Differences in structure (Spanish looking more “compact”, with proportionally shorter and broader wings, and a longer tail than Eastern, and showing a heavier bill and more robust head/neck) are somewhat variable, and probably of little use in the field for separating both species.

The ID criteria still has te be worked out, and an in-depth study, mainly with known-age birds, is badly needed, especially for separating the most difficult, intermediate transitional plumages .

So here are a few photos of some tricky plumages of SIE:

  • Most fresh juvenile Spanish Imperial Eagles show uniformly rich warm rofous, almost unstreaked, underparts. Upperparts usually lack many distinct pale spots or streaks. Thus, they are very different to juvenile Eastern Imperials. See 2 photos below of typical juvenile adalberti.

Spanish Imperial Eagle (Aquila adalberti). Fresh Juvenile. Valladolid, July 2012. Photographer: Juan Sagardía.
A typical juvenile SIE, showing uniformly warm rufous colouration on the underparts, with very little streaking on the chest.

Spanish Imperial Eagle (Aquila adalberti). Juvenile. Ávila, February 2012. Photographer: Juan Sagardía.
Another typical juvenile, with no streaking on the chest, and plain rufous underparts and underwing coverts. The photo was taken in a mountain area of central Spain, certainly less sunny  in the winter than southern Spain or Morocco. Therefore, the plumage state of the bird is still good, not worn or bleached at all being February. Birds wintering in more southerly, sunnier, areas are more prone to bleaching, and by mid winter can be already very worn and whitish.

  • However, some juveniles can show quite extensive evenly dark and pale streaking on the breast, much more so than what´s depicted on most of the guides, and can lack the warm rufous colour of the classic birds, having a  paler, colder, background colour instead. They can also show striking whitish tips to the median and lesser coverts, and also obvious pale spots and streaks on the mantle and scapulars.

Thus, they can be relatively similar to juvenile Eastern Imperials to the unaware observer. Note though that they tend to show little streaking on the underwing coverts, less streaking on the upper-belly, and almost none on the lower breast, than classic heliaca. See some examples of such birds below:

Spanish Imperial Eagle (Aquila adalberti). Central Spain, Autumn 2011. Photographer: Juan Pablo Fuentes Serrano
A juvenile SIE with notorious streaking on the upper breast.

Spanish Imperial Eagle (Aquila adalberti). Central Spain, Autumn 2011. Photographer: Juan Pablo Fuentes Serrano
Note the overall pale and cold background colour of this bird, and also the striking pale tips to all the wing coverts.

Spanish Imperial Eagle (Aquila adalberti). Juveniles. Photographer: Jose Luis Rodriguez. Photo taken from Jose Luis Rodriguez website.
Note the heavy upper breast streaking of the juvenile on the left, similar to that of Eastern.

Spanish Imperial Eagle (Aquila adalberti). Juvenile. Photo: Jose Luis Rodriguez.
A fairly pale bird, with obvious streaking on the upper breast. Note however little streaking on the underwing coverts, unlike heliaca.

A typical juvenile Eastern, for comparison:

Eastern Imperial Eagle (Aquila heliaca). Juvenile. January 2011. Oman. Photographer: Daniel López- Velasco

Below, a darker, and more rufous, Eastern, but with very heavy streaking on the breast and underwing coverts. Such heavy streaking, especially on the lower breast and underwing coverts, shouldn´t be found even in the more streaked extremes of juvenile Spanish.

Eastern Imperial Eagle (Aquila heliaca). Juvenile. January 2011. Oman. Photographer: Daniel López-Velasco

From above, certain birds can be almost identical. See the 2 shots below, both taken in January, showing a juvenile Spanish on the left, and a juvenile Eastern on the right.

Left – Spanish Imperial Eagle (Aquila adalberti). Juvenile. Avila. January 2010. Photographer: Juan Sagardia. Right – Eastern Imperial Eagle (Aquila heliaca). Juvenile. Oman. January 2011. Photographer: Daniel López Velasco
Note the similarities between these 2 birds, although the white tips of the upperwing GCs are broader in the Eastern. A view of the underparts should ID both, though.

  • Apart from the previous pitfall, worn juvenile Spanish Imperials, especially those wintering in more southerly, sunny, latitudes, can be quite bleached in winter and spring, and can look very pale, with cold sandy-buff or even whitish upperparts, and also very pale, worn, upperwing coverts. They can be very similar to pale belisarius Tawny Eagles, and also to fulvescens GSE.

Left -Tawny Eagle (Aquila rapax), Namibia. Photographer: Ignacio Yufera. Photo taken from Ignacio´s website. Right – Spanish Imperial Eagle (Aquila adalbert). Juvenile. Southern Spain, December 2009. Photograher: Javier García.
Note the great similarities between a pale Tawny Eagle , on the left, and a bleached, pale sandy juvenile Spanish Imperial, on the right. No wonder how some of the latter have been wrongly identified as Tawny over the last few years in Morocco. For a correct identification, note smaller size and more compact structure of Tawny, with a shorter tail and shorter wings. Perched, Tawny lacks SIE´s tail/wingtip projection. It also lacks any streaking on the upper breast, usually evident even on worn SIE (see photo). Pale Tawny usually lacks obvious whitish tips to the wing coverts, mantle and scapulars, and they don’t usually show such a noticeable pale, inner primaries window as in Imperial. However, some of the differences can be difficult to judge, and good views and photos would help a lot with the identification.

Spanish Imperial Eagle (Aquila adalberti). Juvenile. Southern Spain. December 2011. Photographer: José Arcadio.
Another example of an already bleached, pale sandy buff juvenile SIE.

Some older, worn birds, in spring, such as the 3cy below, can show uniformly pale underparts, and very worn wing coverts, and can still be very similar, like bleached juveniles, to fulvescens GSE.

Apart from size and structure differences, fulvescens tends to show a more obvious pale crescent on the base of the primaries, more solidly black, almost complete, undersurface of greater coverts, and more uniformly looking dark primaries, with only a diffuse pale inner primaries window.

Left – fulvescens Greater Spotted Eagle (Aquila clanga). India. Photographer: Tejas Soni / Indian Nature Watch. Right – Spanish Imperial Eagle (Aquila adalberti). worn 3cy. June 2009. Southern Spain. Photographer: Antonio Cavadas.
Mainly bleached Juvenile, but also worn, older Spanish Imperials, such as the 3cy on the right, can be very similar to fulvescens GSE. The pale, sandy buff colour of both, upperwing pattern, etc… are almost identical. Good views, mainly of the underwing pattern (fulvescens showing more solidly black, almost complete, under-surface of the greater coverts, and usually lacking a prominent inner primaries pale window), as well as a correct judgement of size/structure, are essential for telling them apart.

  • Immature Spanish, mainly 3cy-5cy,until they start to show pure white feathers on the leading edge of the wing, are in some cases, as already commented, very difficult to separate from Eastern. At least, on actual knowledge.  More work is needed to try to improve this in the future..

They can show obvious dark/pale streaking on the breast, and on the older ages, a mix of dark brown adult- type  feathers and pale, yellowish, whitish,  rufous or buffy, immature-type feathers. The ones with warmer, rufous, immature type feathers, being somewhat easier to ID. But some of them with a cold looking, yellowish, background colour,  Thus, very similar to Eastern.

Some examples of different age classes of Spanish Imperial below, showing variation. There are few published pics of these plumages, so they might be of interest.

…and compare with some Easterns. Similar, aren’t they..?

Spanish Imperial Eagle (Aquila adalberti). 3cy. 31-7-2011. Navarra. Photographer: José Ardaiz.
Note 2 moult waves on the primaries of this 3cy, and the 2 outermost juvenile primaries. The bird shows notorious dark and pale streaking on the upper breast, but the head, part of the underparts and underwing coverts are typically warm rufous.

Spanish Imperial Eagle (Aquila adalberti). 3cy. 4-6-2011. Aragon. Photographer: Alberto Bueno.
Another 3cy, more advanced in terms of primary moult, with no juvenile primaries left, than the above bird. Note, again, obvious streaking on the chest, and relatively cold looking underparts and underwing coverts. See, however, the fairly warm rufous head of this individual, typical of Spanish.

Eastern Imperial Eagle (Aquila heliaca). 3cy. January 2011. Oman. Photographer: Daniel Lopez-Velasco.
For comparison, A 3cy Eastern from January. Outer primaries still juvenile, thus very worn and ragged. Note the heavier streaking on the breast and underwing coverts compared to the above 3cy Spanish.

Spanish Imperial Eagle (Aquila adalberti). Presumed 4cy. Central Spain. Photographer: Jose Luis Rodriguez. Photo taken from Jose Luis Rodriguez website.
This presumed 4cy bird (not possible to confirm the ageing on this photo alone), still, apparently, with no white on the leading edge of the wing, is probably impossible, on actual knowledge, to separate with confidence from the corresponding plumage of Eastern. ID mainly based on location.

Spanish Imperial Eagle (Aquila adalberti). Presumed 5cy. Photographer: Jose Luis Rodriguez.
The first white feathers on the leading edge have already appeared, which helps separate it from Eastern.

Spanish Imperial Eagle (Aquila adalberti). Presumed 5cy. 25-5-2011. Central Spain. Photographer: Antonio Cavadas.
If no pure white feathers on the leading edge of the wing can be seen (and beware of light effects), then the ID of birds like this one can be very tricky.

Spanish Imperial Eagle (Aquila adalberti). Presumed 5cy. 14-6-2011. Valladolid. Photographer: Juan Sagardia

And below, a 5cy Eastern, from Oman. Note how scarily similar the bird is to the above 2 Spanish.

Eastern Imperial Eagle (Aquila heliaca). 5cy. January 2011. Oman. Photographer: Daniel López-Velasco

There are already records of Spanish Imperials in France, and even in the Netherlands , so any vagrant Imperial Eagle should be fully checked and documented, just in case…

And last, thanks to Juan Sagardía and Guillermo Rodriguez for his comments and input on the subject.

Advertisements
This entry was posted in Raptors, Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s