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Tern, Common

Identify and index birds in Southern Africa

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arks
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Re: Identification Help - General Birds

Unread postby arks » Fri Mar 08, 2013 1:58 am

This tern has me stumped :wall: I'd first thought it might be a little tern, but the legs are red, not yellow. So might it then perhaps be a roseate tern? Seen at Strandfontein (Cape Town) on 8 December 2012.

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Re: Identification Help - General Birds

Unread postby Bush Baptist » Mon Mar 11, 2013 1:21 pm

Arks, maybe a juvenile whiskered tern?

I am not great on terns.
Whatever (according to BB): "You are correct but I don't want to admit it".

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Re: Identification Help - General Birds

Unread postby Johan van Rensburg » Thu Mar 14, 2013 9:16 am

The tern is not so easy, tho'

It is definitely not Roseate, the tail streamers being way too short. I also think it is not a whiskered tern because the top of the tail is too white and forked too deeply. The date is wrong to have adult whiskered terns not showing signs of at least some moulting into breeding colours.

Time (Dec) is wrong for antarctic tern which I initially favoured.

So, let me ponder this one some more... :hmz:
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Re: Identification Help - General Birds

Unread postby Johan van Rensburg » Thu Mar 14, 2013 10:44 am

By process of elimination I rejected all the relevant terns! :lol:

So Niall guided me to common tern, one of the birds that I excluded because in non-breeding plumage it is not supposed to have such an extensive white crown. Rightly so Niall reminded me that bill shape and size is the ultimate ID tool when looking at terns especially when the birds are sitting on the ground, the difference in bill shape (sometimes very subtle) is the most obvious and dependable feature. Roberts describes the bill for a non-breeding common tern as black, sometimes with red tinge at base; fairly long with the upper mandible slightly decurved towards the tip.

So what we have here is a common tern in odd moult.

(Thanks Niall!)
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Re: Identification Help - General Birds

Unread postby arks » Thu Mar 14, 2013 2:30 pm

Johan van Rensburg wrote:By process of elimination I rejected all the relevant terns! :lol:

So Niall guided me to common tern, one of the birds that I excluded because in non-breeding plumage it is not supposed to have such an extensive white crown. Rightly so Niall reminded me that bill shape and size is the ultimate ID tool when looking at terns especially when the birds are sitting on the ground, the difference in bill shape (sometimes very subtle) is the most obvious and dependable feature. Roberts describes the bill for a non-breeding common tern as black, sometimes with red tinge at base; fairly long with the upper mandible slightly decurved towards the tip.

So what we have here is a common tern in odd moult.

(Thanks Niall!)

Many thanks BB, JvR and Niall :thumbs_up: I must say that the illustrations for common tern in my Newman's are nothing like this bird (which would be a lifer for me) and I was still puzzled by those red legs. However, I've done a bit of searching and have found a couple of photos here that show similar birds.

That's what so great about this forum! I'd never have figured this one out by myself, but with such expert 'helpers', I'm again learning more! :dance: Many, many thanks!
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Tern, Common

Unread postby wildtuinman » Tue Apr 02, 2013 11:17 am

As one of the medium-sized Terns it can be quite tough at times to id.

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Re: Tern, Common

Unread postby Johan van Rensburg » Tue Apr 02, 2013 12:04 pm

The common tern can basically be confused with Artic, Antarctic and roseate terns. The bill shape is in all cases dianostic. For the common tern the bill would be long and the top mandible slightly decurved near the tip; colour can vary from bright red to black. One useful tip to remember is that in non-breeding plumage, the CT often shows a small ivory tip (diagnostic!!) So, getting a good shot of the bill is critical. Other features that will add to the overall picture and aid in correctly identifying the tern are:
Length, thickness and colour of the legs;
Upper- and underwing patterns;
Rump and tail patterns;
Size and giss.

Also important: read up about the distribution and seasonal appearance of the different species... that will greatly assist in scratching some possibilities.

Image


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Bill descriptions for the other terns in relation to the common tern are:
Artic - shorter and straighter
Antarctic - shorter, heavier
Roseate - longer, thinner
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Re: Tern, Common

Unread postby DotDan » Thu Apr 04, 2013 9:27 am

Great close-ups there Johan.

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Re: Tern, Common

Unread postby Johan van Rensburg » Thu Apr 04, 2013 3:20 pm

Thanks DD. Leopard-crawling on the beach... :lol:

Not a clever tactic tho'... I'm sure you can imagine what happened the first time thereafter when I used my bins to look at another tern-in-flight!
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Re: Tern, Common

Unread postby DotDan » Thu Apr 04, 2013 3:50 pm

Sandy eye? :lol:

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Re: Tern, Common

Unread postby wildtuinman » Thu Jan 01, 2015 6:31 am

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