Greater, Lesser or Hybrid Spotted Eagles (1 Viewer)

[ggregory71]

This bird (please see attached photographs) has already been discussed on this forum, but further matters concerning the two species and hybrids have been raised. These include:
GSE and LSE hybridise commonly
GSE may become endangered in East Europe
birds wintering in or migrating through Middle East cannot often be specified
past definite records in Kuwait (and elsewhere?) may have to be downgraded

Since this matter is of great identificatory, recording and conservation interest, I ask for all possible opinions about the matter. In particular I ask if hybrid eagles are identified as such at the big Middle Eastern raptor migration sites, or are they sometimes logged as Eagle sp, or what?
Below are the exchanged emails (with some spelling corrections) in reverse order:

Hi AbdulRahman & Mike,
This is confirmation from Dick Forsman regarding the eagle that I photographed in March this year. First I received opinions stating that the bird is everything else but Lesser Spotted Eagle. Soon after that I received e-mail from Richard Porter where he confirms that the bird is indeed Lesser Spotted Eagle. I was confused and I almost forgot the bird. My friend Markku asked recently about ID of this bird and I finally contacted Dick Forsman. You´ll see his opinion below. Outcome of his explanation, as far as I can undestand, is that we should cancel all earlier records that are not supported with appropriate photographs. I'm not sure but I tend to think that this concerns all of them.
With best wishes,
Pekka

Hi Pekka,
This is an interesting and a tricky case. Despite the good pictures the id. is not straightforward, which is not how it should be. The bird is an adult or near-adult, as it shows no more barring to its flight feathers and also lacks the spotting of the upperwings. The barring of the underwing is diagnostic in the two species, and helps also to identify hybrids, which are common between the two spotted eagle species. Adult Greater Spotted Eagles would normally show a less obvious contrast above, but stretching the criteria a bit, the bird could match a faded old GSE. Adult Lesser Spotted Eagles would normally show a more distinct contrast above, showing more sandy brown coverts, but again, this could match also a darker-than-average adult Lesser Spotted. The almost non-existant pale bases to the inner primaries are very similar to adult GSE, while most LSEs have a wider pale area across the inner hand, but again, there is much individual and age-related variation in this character. Looking at the underparts, the bird shows mixed characters also here. As a rule adult GSEs show a very conspicuous and broad white crescent at the base of the outer 3-4 primaries. This bird lacks it. Adult LSEs normally show a faint and narrower crescent at the base of the outer primaries, while the bases of the greater primary coverts show more clearly pale bases, forming a long and narrow inner comma. This bird shows the inner comma to some extent, but not as clearly as a typical LSE. Often the wing-formula is different between the two species when comparing birds of similar age, with GSE having a longer 7th primary and a broader, more square-cut wingtip than LSE. Although this bird shows a shorter 7th p than most adult GSEs, this type of wing-tip could be found in both species, so again no help. The overall colour of the underparts body plumage is very similar to ad LSE, but old GSEs can be similarly medium to pale brown. The only thing that really is of relevance in this case is the iris colour. In LSEs of this age the iris should be pale, yellowish or amber, and would stand out clearly in a picture like this. In GSE the iris doesn't get yellowish, but remains dark brown to chestnut even at old age, making the eye look dark in situations like this. I find this a reliable character whenever possible to note. My conclusion is, that this bird cannot be safely identified, since it shows no diagnostic characters, except for the eye-colour. Personally I believe, that this bird could well be a hybrid, carrying a mixture of genes from both species. At least this option cannot be excluded. The eye-colour, the general structure and the wing-shape could match GSE, while the carpal area below and the general coloration show signs of LSE influence. Hybrids between these two species are so common in E Europe today, that researchers fear that GSE will disappear as a pure species from E Europe in the foreseeable future. This fact has, however, not been accepted by the majority of birders, perhaps because it makes an already difficult matter more or less impossible. The juveniles and younger immatures can in many cases be identified as hybrids, sporting a mixture of characters from both species, but the adults, as in this case, remain practically impossible to identifyin the field. Not only are there hybrids, but these hybrids have proved to be fertile and back-crossings between hybrids and eg. LSE are common, creating birds which are mostly one species, with just a fraction from the other. How can you ever expect to tell these birds from the real thing? I think that the fact, that birds looking like LSEs today winter commonly in the Middle East, thousands of kms north of where they should be, is another sign of widespread hybridisation. These birds may look like LSEs, but the GSE genes they are carrying have changed their migratory habits. I saw birds like this only some days ago in Sharm-el Sheikh, Egypt, where they occurred side by side with pure GSEs.
Dick Forsman

Pekka Fagel kirjoitti:>
Hei Dick> Kuten oheisista e-mailesta näkyy, yritin selvittää jo keväällä täällä Kuwaitissa kuluvan vuoden maaliskuussa kuvaamani kotkan määrityksen. Sain keväällä joitakin vastauksia, joissa kuvan lintu todettiin olevan kaikkea muuta kuin pomarina.> Sitten tuli yllättäen Richard Porterin maili, jossa hän toteaa sen olevan pomarina.> Olisin kiitollinen jos ehtisit arvioimaan kahta kuvaani ja erityisen iloinen jos voisit vastata englanniksi.>
Terveisin> Pekka Fågel> Mahboula, Kuwait>

----- Forwarded Message ----> *From:* Pekka Fagel <[email protected]>> *To:* Rami Lindroos <[email protected]>> *Sent:* Monday, November 24, 2008 5:07:32 PM> *Subject:* Fw: Lesser Spotted Eagle?>
> Hei> Tästä oli jo keväällä keskustelua ja minun on pitänyt lähettää kuvat myös Dick Forsmanin arvioitavaksi, mutta asia jäi kun en löytänyt hänen sähköpostiosoitettaan. Tämä kuitenkin kiinnostaa sen verran, että haluasin tuon harjoituksen tehdä semminkin kun Richard Porter lähetti tämän ohessa olevan e-mailin. Oletan, että sinulla on hänen osoitteensa.. Voin toki lähettää itsekin kuvat hänelle jos välität tuon osoitteen.>
Terveisin> Pekka> >

----- Forwarded Message ----> *From:* richard porter <[email protected]>> *To:* Peter Cowan <[email protected]>> *Cc:* Pekka Fagel <[email protected]>> *Sent:* Sunday, April 6, 2008 12:43:35 PM> *Subject:* Re: Lesser Spotted Eagle?>
> Dear Peter (and Pekka)>
Thanks. This has to be an adult Lesser Spotted, surely: correct wing formula, contrast between brown under/upperwing coverts and darker flight feathers, and slightly darker brown back cf wing coverts (a subtle point that I find holds true on most (all?) LSEs).> The white flash on the upperwing is good for LSE (though probably OK for GSE too - bit difficult to see clearly) and the white on the uppertail coverts is fine. Interestingly there is an almost identical photo in Dick Forsman (plate 408), even showing a white streak/patch on the back.> I agree that the bill does look large but it is open and that can make such a difference to the impression it gives. And, of course, there is quite a lot of size variation anyway between males and females.> Hope this helps in the debate.>
Best wishes>
Richard> >

Original Message -----> *From:* Peter Cowan <mailto:[email protected]>> *To:* [email protected]> <mailto:[email protected]>> *Cc:* Pekka Fagel <mailto[email protected]>> *Sent:* Sunday, April 06, 2008 9:18 AM> *Subject:* Fw: Lesser Spotted Eagle?> >
Dear Richard,> > As you may know Kuwait birding is particularly vibrant at present.> One of its leading lights, Pekka Fagel, has sent me the attached> ?Lesser Spotted Eagle pics. Is he correct to doubt the ID? Sorry> to have attempted to add to your intray!> >
Best wishes,> > Peter> > Dr Peter Cowan> Department of Biological Sciences and Chemistry> University of Nizwa> Sultanate of Oman> >

--- On *Thu, 3/27/08, Pekka Fagel /<[email protected]> <mailto[email protected]>>/* wrote:> > From: Pekka Fagel <[email protected]>> Subject: Lesser Spotted Eagle?> To: "Peter Cowan" <[email protected]>, "George Gregory"> <[email protected]>> Cc: "Abdulrahman Alsirhan" <[email protected]>, "Gary> Brown" <[email protected]>, "Brian Foster"> <[email protected]>, "Mike Pope"> <[email protected]>, "Rauli Lumio" <[email protected]>> Date: Thursday, March 27, 2008, 7:21 AM> >
Hi Peter & George>
I photographed this Lesser Spotted Eagle-type bird at Pivot> Fields on March 25th. It shows very typical contrast on wings> but it's bill looks too big and also tail is somehow not> matching. What do you think? I have sent same pics to> Alula-team too.>
Best regards>
Pekka> >

 

[Jos Stratford]

... further matters concerning the two species and hybrids have been raised.
These include:

GSE and LSE hybridise commonly

They do hybridise, but I believe this is of far more regularity where GSE are at the extreme edges of their range, eg in Estonia, etc. In the core of the range, I would suppose it is far less frequent.
I think for many species, not just eagles, this is reasonably normal on the edge of ranges, where presumably members of the 'correct' species become less 'available'. Aside eagles, Blyth's Reed Warbler is also a regular hybridiser in this area and Hooded Crows are another obvious example, are many terns and gulls.

Concerning identification of GSE and LSE, there are individuals (I believe an absolute minority of birds) that are unidentifiable, but whether this is due to them being necessarily hybrids is another question. Both eagle species are extremely variable and I have recently been looking at pictures that in many respects appeared to be GSE, but on consideration were certainly LSE, (proven to be so as both parents were pure LSE, a fact I hadn't been informed when looking at the pictures).

GSE may become endangered in East Europe

They are endangered in East Europe

 

[ggregory71]

A few points to consider:
(1) Presumably the hybrids or back-crosses become infertile after several generations. If they remained permanently fertile then GSE and LSE would be one species, according to the traditional definition of such. However, while present in the breeding population, these birds would reduce the numbers of the pure birds, causing genetic endangerment, similar to that caused by escaped falconers' hybrids.
(2) Is this hybridisation something relatively new, or has it just been realised recently? If the latter, then perhaps past records (especially if involving specimens), including those in the UK, should be re-examined.
(3) Some GSEs are or have been recorded as wintering in southern Europe. Have these birds been rigorously examined to exclude hybrids?
(4) If in the future a Spotted Eagle sp arrives in the UK (or in another country where it would be a major rarity) on an easterly wind, likely from the zone of overlap/hybridisation, then consideration of hybrid status would be essential.
(5) I do not know what to recommend about the past records in Kuwait - perhaps a caveat about hybrids would be the best option. Not all records involved wintering birds. Recorders in other Gulf states presumably would have a similar problem.

 

[jurek]

You should contact Mr Meyburg and mr Mizera (google them), who are studying Greater Spotted Eagles in Poland and perhaps laid their hands on most of breeding population.

As far as I remember, subject of LSExGSE hybridization was floating around for years. Opinions were changing how common it is, from that no pure GSE exist in Europe to that it is rare and occassional occurence. Its still poorly understood thing, as are GSEs.

Surely, there are now hybrid pairs in Poland, but on the "core" range in Russia, GSE is not in contact with LSE at all.

The whole topic is muddled severalfold. Both species are very similar visually and genetically anyway, there are no genetic tests of so-called hybrids, studied population of GSE is just about a dozen of pairs surviving in Poland, main population of GSE lives in inacessible Belarus and Russia.

 

[Joern Lehmhus]

A few points to consider:
(1) Presumably the hybrids or back-crosses become infertile after several generations. If they remained permanently fertile then GSE and LSE would be one species, according to the traditional definition of such. However, while present in the breeding population, these birds would reduce the numbers of the pure birds, causing genetic endangerment, similar to that caused by escaped falconers' hybrids.

I don´t know any proven example for such a case as you described, if you have an example i´d like to know it.


The traditional definition of a species is a bit faulty, concerning fertility of interspecies crosses.
If the first generation hybrids are fertile, I wouldn´t expect later generation hybrids or backcrosses to one of the parent species be infertile.
In ducks, if first generation hybrids are fertile, also later generation hybrids or backcrosses seem to be fertile.For example Mallard and Pintail produce fully fertile hybrids, and also backcrosses with one parent species and later generation hybrids are fully fertile.
However, if there are behavioural or ecological barriers for hybridisation, two or more related species can live in the same area without merging into one species (like mallard and pintail for example) ; the few hybrids that might occur would not influence the populations gene pool much (even if they have similar fitness as a parent species).

But I am thinking along the following lines: If we have two species separated ecologically, one living in dense woodland and the other in open country. and the landscape is altered by partially felling the woods so that you get a landscape mosaic with open country and woodland intermixed, then on the one hand the two species would have an increased contact zone and hybridisation might occur more often than earlier .

Now imagine the hybrids have an increased fitness in the altered habitat compared to the parent species...maybe for example through more efficient utilisation of the altered habitat;
or maybe through an intermediate migration strategy which puts them into advantage compared to one or both parent species...

these are crude examples and I do not know too much about the two eagle species involved here...so i do not know if this fits on this situation, but I think such scenarios probably happen....

 

[gerdwichers8]

Here is the original thread
http://www.birdforum.net/showthread.php?t=110355