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Black-throated Diver or Great Northern Diver?

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Old Thursday 29th November 2007, 18:13   #1
Henrik Johansson
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Black-throated Diver or Great Northern Diver?

Black-throated Diver or Great Northern Diver?

http://www.fugler.net/nye/bilder/bilde.asp?bildeID=8471

http://www.fugler.net/nye/bilder/bilde.asp?bildeID=8473

Eastern Norway, Nov 2007
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Old Thursday 29th November 2007, 18:14   #2
jacana
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black throated diver i think due to the rounded head, and the beak isn't as massive as i would expect for a GN diver
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Old Thursday 29th November 2007, 18:48   #3
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Gut feeling is GND but I have to admit it looks rather small
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Old Thursday 29th November 2007, 18:48   #4
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I'd go with Black-throated - on plumage, bill and head shape.
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Old Thursday 29th November 2007, 18:51   #5
Nicola Main
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I agree with Jacana and Birdbox. A Black-throated Diver.
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Old Thursday 29th November 2007, 19:48   #6
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I go against the flow im afraid.
I think the second one is GND and the first one probably is as well even though its showing a bit of neck and looking Black Throated.
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Old Thursday 29th November 2007, 20:01   #7
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Black-throated diver for me for reasons others have said.
too rounded head
lack of half collar markings on neck
slimmer than a GND bill
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Old Thursday 29th November 2007, 20:47   #8
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I would say GND especially the second pic coz I can't see a prominent white flank patch which one would expect on a BTD but that could be the choppy water.
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Old Thursday 29th November 2007, 21:09   #9
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I'm in the BTD camp as well, for reasons already made.

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Old Thursday 29th November 2007, 21:11   #10
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I would say this is a real oddball! Extent of dark coloration on ear-coverts suggests GND, but the demarcation between fore- and hind-neck seems to be straight line, without the pale indentation of GND. Head looks rounded in pic 1, flat-topped in pic 2. Pacific Diver/hybrid, anyone?
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Old Thursday 29th November 2007, 21:20   #11
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Probably GND based on those pics, but would like to see more.

Obvious barring on the back in the 2nd pic suggests it's a juvenile diver.

Whilst it doesn't show the kind of half collared effect often seen on GND the colour of the crown and nape look on the dark side for a BTD (usually greyer), and the dark on the 'face' comes down below the eye more in line with the bill which is better for GND, BTD tends to have a pale 'cheek' and a lot of white round under the eye.

Don't think you'd be able to see if it had a white patch at the rear of the flanks in those pics due to the sea state and angles.

Edited to add to MSA comments - Pacific should have a similar 'face' to BTD.

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Old Thursday 29th November 2007, 21:22   #12
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Quote:
Originally Posted by MSA View Post
I would say this is a real oddball! Extent of dark coloration on ear-coverts suggests GND, but the demarcation between fore- and hind-neck seems to be straight line, without the pale indentation of GND. Head looks rounded in pic 1, flat-topped in pic 2. Pacific Diver/hybrid, anyone?
Don't think its an oddball Mark the bird facing slightly away giving the impression of the head and neck having more extensive dark areas than it actually has.

Also head shape changes with posture, GNDs head would never look as rounded as shown in first pic, but BTD can often look as 'moderately lumpy' as shown in 2nd pic.

Straightforward BTD for me. I have IDed divers confidently from greater distances than this so if was wrong I would be in serious s**t, also was studying a local GND only yesterday so its fresh in my mind.
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Old Thursday 29th November 2007, 21:30   #13
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Don't think its an oddball Mark the bird facing slightly away giving the impression of the head and neck having more extensive dark areas than it actually has.

Also head shape changes with posture, GNDs head would never look as rounded as shown in first pic, but BTD can often look as 'moderately lumpy' as shown in 2nd pic.

Straightforward BTD for me. I have IDed divers confidently from greater distances than this so if was wrong I would be in serious s**t, also was studying a local GND only yesterday so its fresh in my mind.
If pushed, I'd agree that on balance it has too many "non GND" features to be anything other than BTD to me - I'd be more confident with the bird in front of me than passing judgment over a couple of pics, though
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Old Thursday 29th November 2007, 22:29   #14
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HELL i have just realised its not two birds at all but two shots of one bird. I must stop to read and not just crash on. looking at both photos again and listening to every thing said i still go for GND. I agree with Mark tho it would be easy resolved with a look through some bins.
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Old Thursday 29th November 2007, 22:31   #15
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In my (most humble) opinion - this is a 2nd cal winter GND - I'd see no problem with bill size at all - colour (what there is of it) appears fine. Most important (in my experience) is B-tD would have a much more extensive pale/white cheek - this bird (in both pics) shows non of that, showing a straight demarcation from gape and through the neck.
Just a point of view
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Old Thursday 29th November 2007, 22:58   #16
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one of the two larger divers, prob GND. Main points mentioned but has a nice pale eye surround too
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Old Thursday 29th November 2007, 23:49   #17
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drunken gut feeling says GND, don't ask why, I don't know.
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Old Friday 30th November 2007, 00:00   #18
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Originally Posted by timwootton View Post
In my (most humble) opinion - this is a 2nd cal winter GND - I'd see no problem with bill size at all - colour (what there is of it) appears fine. Most important (in my experience) is B-tD would have a much more extensive pale/white cheek - this bird (in both pics) shows non of that, showing a straight demarcation from gape and through the neck.
Just a point of view
Having just looked a breif look at your website I find very difficult to argue with a professional bird artist who lives in the orkneys (think there might be a few more GNDs around there than around Bolton aswell). Also other opinions from northern reaches think its a GND

Oh well, although not sure of identity looks like I have some correcting to do with my overconfident Ids from my seawatches. How people seperate these 2 with the distances involved on seawatches is mystery to me.

Retires to bed, after a cuppa with egg on face.

Never liked seawatching anyway

Last edited by Steven Astley : Friday 30th November 2007 at 00:09.
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Old Friday 30th November 2007, 00:05   #19
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drunken gut feeling says GND, don't ask why, I don't know.
drunk on a Monday night, typical french (was going to say frog but is that too offensive). Know the french are sensitive people
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Old Friday 30th November 2007, 00:09   #20
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drunk on a Monday night, typical french (was going to say frog but is that too offensive). Know the french are sensitive people

Is it Monday? Sh*t, I was hoping for the weekend sooner than that! Frog's not offensive, I say it to all the French and I'm still allowed to live here! Back to topic, I agree about divers while seawatching, not much sea around here luckily. One BT Diver on a boating lake and a few GNDs on UK reservoirs, it's a lot easier then!
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Old Friday 30th November 2007, 03:09   #21
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Big head, thick neck, appears to have, if anything, a hint of an upturn to the bill. Pale eye-surround on one shot all point me to juv. GND.

Doesn't really have the serpentine curves of a BTD, at least from these shots.
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Old Friday 30th November 2007, 07:19   #22
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Having just looked a breif look at your website I find very difficult to argue with a professional bird artist who lives in the orkneys.

How people seperate these 2 with the distances involved on seawatches is mystery to me.
Hi Steven - just because I'm an artist doesn't make me any better at ID - I'm pretty useless most of the time (and you'd only need to see my paintings to know that )
And I definitely agree with your second comment - they are b100dy hard to pick, a lot of the time.
Cheers - Tim
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Old Friday 30th November 2007, 09:05   #23
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Hi, my first impression was GND, but on a second look that bill looks very pale and erm yellow (not pale grey), and the lower mandible appears to bulge outwards then curve up towards the tip.........
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Old Friday 30th November 2007, 09:21   #24
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Hi, my first impression was GND, but on a second look that bill looks very pale and erm yellow (not pale grey), and the lower mandible appears to bulge outwards then curve up towards the tip.........

head is too dark for White/Yellow billed if that's what you're thinking. GND for me, they are often rather pale billed and wouldn't want to judge colour from these pics.

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