KNP Raptor - Brand new Pics!

  • mossie
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10 years 9 months ago #3752 by mossie
mossie replied the topic:
Hi All

I must say, I agree with Trevor on this. My reasons are thus: when it comes to determining species, which is roughly defined as a group of individuals, who are genetically closely related enough to be able to recognise each other as a mate, then we have quite a lot of options with which we can use to group related individuals into species. Unfortunately, as birders, we use the obvious phenotypes like colouration as our first port of call, and then move on to shape, song, habits, etc.

Here comes the problem. This group of eagles are notoriously variable with regards to colouration. For a number of species, colouration can be changed by a single gene, and can often be as little as a single nucleotide substitution. So a Browny (Dark form of a Tawny) is definitely going to set us all off on the wrong foot. But to an eagle, all the other features are the same, and it is easy to recognise each other as potential mates.

Since genetic studies are out of the question, as a diagnostic tool, the next most reliable thing to look at, are gross morphological characteristics, with the premise being, that it is difficult to change the genes to cause changes in body shape, without affecting functionality. So you have to now look very carefully at the pictures that Trevor presented, and measure for yourself, the various proportions of the facial features of the birds.

Hopefully, you will be able to see that the eagle is a lot more tawny than lesser spotted. It is just the nostril that is a little atypical, but probably could pass as tawny.

Mossie (trying to make this thread 4 pages)

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  • Trevor Hardaker
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10 years 9 months ago #3753 by Trevor Hardaker
Trevor Hardaker replied the topic:
Hi there,

It would seem that one is never too old (or too young…) to learn and I have just had all my ideas of large brown eagle identification thrown into turmoil this morning. It would appear that everything I thought I knew on how to separate Tawny from Steppe Eagles actually holds no water at all! I took the liberty of contacting the world authority on raptors, Dick Forsman, to ask his opinion on this bird. Here is what he has to say:

“Hi Trevor,
To me this looks like a standard adult Steppe Eagle, and I cannot see anything strange about it. Since many of the adult-type Aquila eagles (all other suggestions can be ruled out simply by structure and general
plumage characters) when on the ground are "just brown", one has to look for any diagnostic plumage details to be sure about its identity. In these pictures I can find two characters which are diagnostic of adult
Steppe. The most important is the pattern of the remiges, which can be glimpsed in one of the photos (top one, looking away), where the tertials can be seen. The pale grey tertails with sparse, broad black barring and a wide dark subterminal band are only shown by Steppe. As simple as that. Judge for yourself.
The other character is the straw-coloured nape, which is seen in many ad Steppes, but not all.

The discussion always turns to nostril and gape shapes when the identification of these birds is discussed. My advice is to forget them both! The difference in nostril shape is true, but it is always affected by shadow and light in the field, and can be difficult to assess reliably. Regarding the difference in gape length, I am convinced there is a great deal of overlap between Tawny and Steppe in the first place, and further, the alignment of the eye in relation to the gape is not constant, but changes according to the viewing angle! Check it for yourself the next time you are face to face with and eagle. By the time you have seen the nostrils or gape well enough, you have probably either flushed the bird, or at least missed a lot of time to go through the plumage, which is where the real id-characters are hidden. On a perched bird look for pattern of secondaries, including tertials, and tail; check upperwing coverts and scapulars for any pale markings, and make careful notes of these. And never miss a chance to check the legs! The two Spotteds have long and thin tarsi, while Steppe and Tawny have short and sturdy legs.

If anything is strange with the Kruger bird it is the head profile. The bird appears to have a strangely shaped bill, which appears small and drooping, compared to the average Steppe. However, if you spend some
more time with a group of eagles, you will soon realize that their faces vary as much as ours, and it is easy to identify individuals by the facial expressions. This one's got the small nose, like Jerry next door.

regards,
Dick”

Now to go back to all the photos I just recently took in the Kruger and see if any of this applies to them…

Kind Regards
Trevor

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  • Doug
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10 years 9 months ago #3754 by Doug
Doug replied the topic:
Hi Trevor.

That is truly awesome information. I thnk that sort of top drawer ID tips are what eventually make these difficult things so much easier.

Thanks for the feedback.

Cheers.
Doug.

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10 years 9 months ago #3755 by Doug
Doug replied the topic:
I got some additional feedback from
Dr. Reuven Yosef from the International Birding & Research Centre in Eilat.

His response was as follows:

Hi Doug -
bassed on the wing feathers, the gape and the "golden" nape, I am convinced this is an VERY adult Steppe Eagle (Aquila nipalensis).


Seems the raptor-files agree.

Cheers.
Doug

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  • gordon
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10 years 9 months ago #3756 by gordon
gordon replied the topic:
Interesting that all of us thought it was something other than a Steppe! (myself included.)

Just shows, as Trevor so rightly says, you never stop learning!

Thanks to everyone for a highly entertaining post!

Cheers,
Gordon

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  • Doug
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10 years 9 months ago #3757 by Doug
Doug replied the topic:
I must say bird books are rather frustrating.
Even the popular Raptors of the World does not really mention the barring on the tertials in Steppe eagle as being particularly diagnostic and if you read the write-ups for the 4 large brown eagle in question, the book seems to contradict itself or at best be rather vague.

I wish to thrown down the gauntlet to any raptor expert that truley knows all these secrets of identification to publish a book that has all these deep dark secrets of raptor identification in it.

Maybe one day we will get to a point where ID information on all species is easy to find. :rolleyes:

Whilst the pipits are not easy I think Faansie has set a new standard for bird books across the world with the most amazing depth of knowledge for identification of pipits he has shared through his book.

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10 years 9 months ago #3758 by j-ms
j-ms replied the topic:
The person who first posted the bird on the SANParks site ("Elsa") has asked me to pass on her appreciation to everyone on Simply Birding who was involved in IDing the bird for her.

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  • Johann
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10 years 9 months ago #3820 by Johann
Johann replied the topic:
Some more photo's of the same bird. Kind thanks to Stuart Bassil from Norwich supplying me with these. If somebody wants the original 3504x2336 images to have a closer look just send me a pm. I only loaded 9 of the 16 images Stuart sent me. Think these have got the best angles.













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  • Doug
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10 years 1 month ago #6122 by Doug
Doug replied the topic:
I have just recently received my copy of the Helm guide to Birds of East Arica. What a book. Why am I posting this point under this thread? When we were discussing this bird, I consulted Sasol, Roberts VI, Roberts VII and both the large and fieldguide versions of raptors of the world and nothing really cleared it up for me. I now looked at this bird with renewed interest using this book and hey presto a good bird book makes it so easy. If I had the Helm guide then I would have immediately arrived at Steppe. If you can get hold of that book, do so. It also has a brilliant page on Issabeline, Northern and Pied Wheatears that does the best job I have seen of covering these difficult to ID species.

Cheers,
Doug.

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