Gull/Tern? from Lake Ziway, Ethiopia (1 Viewer)

[hans-b]

I took the picture at Lake Ziway (Ethiopia), 21.1.2016
If it is not possible to identify the bird the family or genus would also be helpful.

Thanks for your help
Hans

www.boeckler.name

 

[MTem]

2cy Black tern Chlidonias niger

 

[MacNara]

Surely more likely to be White-winged Tern Chlidonias leucopterus which is common in the area, rather than Black Tern which is 'rare...with very few confirmed records'?

 

[KGS]

Surely more likely to be White-winged Tern Chlidonias leucopterus which is common in the area, rather than Black Tern which is 'rare...with very few confirmed records'?

Rump looks very dark for WWT though and nothing I see contradicts BT. Also there seems to be som dark markings at the base of the leading edge of the wing.

 

[MacNara]

Black Tern records are, according to the books, extremely rare in East Africa. If the OP has other photos, it would be worth posting them. And if you're really sure it's Black Tern, then it would be good to report it.

 

[MTem]

Rump looks very dark for WWT though and nothing I see contradicts BT. Also there seems to be som dark markings at the base of the leading edge of the wing.

My reasoning as well, although I was unaware of its scarcity in that region. A photo showing the shoulder more clearly, and confirmation of the presence (or absence) of the seeming black patch would confirm either way.

Bill does look a bit short, but the bird has its head tilted towards the viewer and so it will be fore-shortened a little I think.

Mick

 

[hans-b]

Sorry I have only this picture. I was 5 days in Ziway but I saw this bird only one time.
When I look to www.world-birds.com/birds/a/ethiopia I find Black tern but not White-winged tern. But I do not know how reliable the information of page is.

 

[MacNara]

Well, my quote about Black Tern, 'rare with very few confirmed records' was from Birds of the Horn of Africa' by Redman, Stevenson and Fanshawe, which is the English-language main reference for the area. But it also says that it is 'recorded in most months' which seems to contradict this slightly.

The same book says that White-winged Tern is a 'very common passage migrant and winter visitor'. Whiskered Tern is 'locally common, but not numerous'.

I'm not at all an expert on these Marsh Terns, but they are notoriously difficult to separate in winter plumage, especially if you don't have experience seeing a lot of them. White-winged Tern used to be called White-winged Black Tern. Whiskered Terns which we have where I am seem to vary a lot in non-breeding plumage, and I thought Black and White-winged did too.

But MTem and KGS are undoubtedly much more experienced than me with these birds, and if they think this is Black Tern, then it may well be. If so, you were lucky to find it there.

When we were at Ziway in 2012, also in winter, we saw lots of birds in just a few hours, but no terns, just a couple of Black-headed Gulls. (We saw Whiskered Terns at Lake Tana.)

But if you were there five days, you may well have seen a lot more than us. Did you see any other terns in that time? It would be interesting if you saw only one tern in five days, and it turned out to be the rarest.

I don't know about the site you linked to 'World Birds', but as far as I can see, it doesn't have 'White-winged Tern' in its list of birds at all (for any country). Nor does it seem to have 'Whiskered Tern'. And it mispells the binomial of Black Tern as Chilidonias. And its search function doesn't work well. So I would say it's not reliable at all. It looks like someone has 'scraped' some online source to make a website to make advertising money.

In my experience Wikipedia's list of birds by country are pretty reliable. Here is their list for Ethiopia.

 

[hans-b]

Thank you for your detailed answer.
I'm more photographer than birder. In Ziway I shot a lot of pics of flying birds. At home I saw this bird I never saw before. I also cannot remember that I saw another tern.
I add a second pic (from my backup hd) of the same bird that I had already deleted because it was the worse one of the two I had.

 

[MTem]

Unfortunately this photo doesn't add any further confirmation aspects for me, but it also shows clearly the rump is grey, not white.
Still a 2cy BT for me.
Mick

 

[Jean FRANCOIS]

Rump looks very dark for WWT though and nothing I see contradicts BT. Also there seems to be som dark markings at the base of the leading edge of the wing.

I think of a first winter leucopterus.
See the following images made in the same place and at the same time
http://www.oiseaux.net/photos/pascal.bernardin/guifette.leucoptere.1.html#monde
http://www.oiseaux.net/photos/dominique.cavey/guifette.leucoptere.3.html#monde
Regards.

 

[hans-b]

Thanks Jean Francois, that's it (White-winged tern/Chlidonias leucopterus).

 

[MacNara]

Unfortunately this photo doesn't add any further confirmation aspects for me, but it also shows clearly the rump is grey, not white.
Still a 2cy BT for me.
Mick

It's a pity there is no photo showing the undercarriage, because there is said to be a black side-stripe to the breast which would distinguish between Black and White-winged.

The attached photo is of a bird from Chobe in Botswana at the very end of December in 2014 which I had down as White-winged Tern (just the one photo; Black Tern doesn't appear to be on the list for Chobe). It seems to have a grey-ish rump.

 

[MTem]

What you need to see is the shoulder where the leading edge of the wing meets the body. In the photos Francois has linked to you can see how clean and white this is in a WWT. In a BT there is a black patch that leaks into the neck sides and down onto the armpit a little. This is what I and KGS think we can see the edge of in photo 1, but the angle of the photo is inconclusive. Rump colour is perhaps less strong a diagnostic feature, but BT usually show a grey rather than white colour at this age.
As I said if I saw this bird with only this view in Europe I'd have to go for probable BT, but with the variation that birds can exhibit, and the apparent rarity in that region, I'd also agree that 2cy WWT cannot be ruled out on these images.
Mick

 

[MacNara]

What you need to see is the shoulder where the leading edge of the wing meets the body...In a BT there is a black patch that leaks into the neck sides and down onto the armpit a little. This is what I and KGS think we can see the edge of in photo 1, but the angle of the photo is inconclusive. Rump colour is perhaps less strong a diagnostic feature, but BT usually show a grey rather than white colour at this age.Mick

I'm not so convinced that a slight blackness at the shoulder is that distinctive. We had Whiskered Tern visit us a few times where I live in central Japan (near Osaka) and I thought from photos with a shoulder blackness that we has some other bird. But asking here on BF and elsewhere I was told I was wrong, and that there is a lot of variability anyway.

Attached are a few Whiskered Tern examples from Nara Japan showing some kind of shoulder blackness.

 

[MTem]

This is the level of blackness at the shoulder I'm talking about for a BT. Never seen this on a WWT, although I haven't seen thousands of 2cy's.

http://1.bp.blogspot.com/-30CRxv4ob...4oIgPpaI/s1600/BlackTernStartops31Aug2014.JPG
http://www.vogelwarte.ch/assets/images/voegel/vds/artbilder/700px/2720_1.jpg

... but overall I think I'm agreeing with you! This could well be a 2cy WWT with a greyer than usual rump ....

 

[Tib78]

To my eyes the OP bird is a WWBT. The white rump normaly shown by this species is a somewhat overrated feature in my opinion and there are too many exceptions to consider this is a reliable character.
Here is what I see in favour of WWBT (apart from likelihood at this location):
- strongly peppered black and white crown (vs more solid black in Black tern)
- reduced black ear-patch
- irregular rear edge of the ear-patch (more rounded in BT)
- very little black to the nape
- shortish bill
- very short tail showing a shallow notch