19.11.2010 11:33, Rob Davies kirjoitti:

 

Thanks Dick

Very useful article with nice photos.

Yes I understand the differences between age classes and sexes of large eagles can make separation of close species very difficult.  Many eagles seem to be given a starter kit plumage (shape) quite different from adult plumage.  They do like making it difficult for us which adds to the fun.

Your observation of the untidy trailing edges on adult Steppes is useful indeed and quite unusual on an adult eagle, but I guess this would also be seen on moulting GSEs.  Anyway it is good to entertain different possibilities on identification when the photographs don’t permit 100% certainty, I think that way we can learn more

All the best

Rob

 

 

 

From: africanraptors@yahoogroups.com [mailto:africanraptors@yahoogroups.com] On Behalf Of Dick Forsman
Sent: 19 November 2010 07:23
To: africanraptors@yahoogroups.com
Subject: Re: [africanraptors] Fw: [AfricanBirding] Greater Spotted Eagle at Ndarakwai, Tanzania [1 Attachment]

 

 

[Attachment(s) from Dick Forsman included below]

Hi Rob,
It's all true what you are saying, however, there are a lot more variables involved, which you cannot find in the current literature. 
The fact that both measurements, proportions and even wing-formulas differ HUGELY between adult and juvenile birds in both species cannot be described by the standard measurements. Also males and females of the same species differ in a similar way. Thus, you cannot compare just a species with another species, but the comparison should be made between birds of the same age and sex! This is what I tried to explain, when I referred to differences in shape and size between male and female Steppe. You simply cannot go by measurements or proportions, when identifying birds as similar as GSE and SE are. The identification should always be based on plumage characters, and even so it can be difficult enough at times.
The feather-character I mentioned has been published by me sometime in the 1990's, but seems to have been forgotten since. If you compare adults (only!) of SE and GSE and look at the trailing edge of the wing, the GSE shows broad and neatly rounded secondary tips, while in SE they are more narrowly pointed and create almost a serrated trailing edge to the wing. I think this can be seen in Valery's first image.

I attach a pdf for you on the plumage development in SE, from Alula 1-2005. 

Best regards,
Dick

15.11.2010 18:04, Rob Davies kirjoitti:

 

Hi Dick

I think Steppe Eagles do look a bit longer-winged / thinner-winged than GSE.  I’ve had a look at the measurements and while body length is very similar wingspan can range up to 10cm or so longer on Steppe.  So when you see a more ‘stubby’-looking eagle like this I would have thought it would be a good chance it is a GSE.  Looking at the photos, GSE also seem to have more splay in the primary fingertips esp the inner primaries (no. 4) which seem long black and droopy in this species, maybe that is one of the details you are referring to.

Just some additional obs so that we don’t stop trying to separate these two.

Cheers

Rob

 

 

From: africanraptors@yahoogroups.com [mailto:africanraptors@yahoogroups.com] On Behalf Of Dick Forsman
Sent: 11 November 2010 08:11
To: africanraptors@yahoogroups.com
Subject: Re: [africanraptors] Fw: [AfricanBirding] Greater Spotted Eagle at Ndarakwai, Tanzania

 

 

11.11.2010 9:42, Neil and Liz Baker kirjoitti:

 

thoughts on this silhouette please.

 

thanks

 

Neil
 

Neil and Liz Baker, Tanzania Bird Atlas, P.O. Box 1605, Iringa, Tanzania.
Mobiles: +255 776-360876 and +255 776-360864.
http://tanzaniabirdatlas.com
Subscribe to: tanzaniabirds-subscribe@yahoogroups.com

 

 

----- Forwarded Message ----
From: Valery <valery@valeryschollaert.com>
To: AfricanBirding@yahoogroups.com
Sent: Thu, 11 November, 2010 9:47:55
Subject: [AfricanBirding] Greater Spotted Eagle at Ndarakwai, Tanzania

 

Hi all,

Yesterday morning the eagles were numerous in the Ndarakwai sky. Steppe Eagle was by far the most numerous but the surprise was to find an adult Greater Spotted Eagle amongst them. I'm not really equiped for distant flying birds, but here is a small photo that should show the typical silhouette (short tail, very wide wings).

http://www.valeryschollaert.com/index.php?option=content&task=view&id=1098

It was seen in company of a Steppe Eagle so we could even compare the size and shape. All other needed details such black underwings on slightly greyer flight-feathers were seen with the telescope.

Have a good day

Valéry

Hi all,
The bird looks like a Steppe Eagle to me. Of course, it is impossible to be sure about anything in photos like this, and especially when there is only one image available. However, there are several things in the photo itself, like pinched-in wing-base, long neck and head, tail-shape and most importantly, the ragged looking trailing edge of the wings, which are typically Steppe rather than GSE characters. Another important feature is mentioned in the accompanying brief descriptive text, which mentions the "black underwings on slightly greyer flight-feathers", which again is typical of adult Steppe, whereas adult GSE has uniformly dark fligh-feathers, which are not contrasting as paler against the coverts, if anything, they would appear darker!
Having watched adults of both species together on migration in the Mid-East I would not recommend anybody to id. these birds on shape alone. They look very similar from a distance and plumage details are definitely required. The size and shape difference between adult male and female Steppe is big enough to explain the difference in jizz described by Valéry. 
Regards,
Dick