Common Tern Behaviour?

Liam

Liam

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I went down to the beach yesterday morning hoping to get some images of the rain, but it was to misty and I forgot my waterproof trousers :bang:
Instead I found some terns, as you can see in the below pictures, one of them was fishing for another. Is this a juvenile being fed or some sort of mating behavior? Thanks for any info/comments.

1.

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6. (The sun came out)

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The plumage of the one being fed does not look like a juvenile to me so I can only assume it is mating behaviour. Nice set of shots especially in the rain.
 
The last is superb ...could you crop it a bit and re-post it with the water drops as I think its a super shot
 
Its called "food passing" Its pair bonding behaviour and quite common
among most if not all species of birds
 
Cobra said:
Its called "food passing" Its pair bonding behaviour and quite common
among most if not all species of birds
Click to expand...

....and "juvenile" is another word for "just left the nest", so come the autumn every year there will be no juveniles around. After their first moult, they become "first winter" or "immature", depending on the species.

Nice pics, I really like the low-key background colour. Common Terns, BTW.
 
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jerry12953 said:
....and "juvenile" is another word for "just left the nest", so come the autumn every year there will be no juveniles around. After their first moult, they become "first winter" or "immature", depending on the species.

Nice pics, BTW....
Click to expand...


Without being pedantic :D
The first moult doesn't happen ( begin) until the following late spring early summer and ends late summer / early autumn
So they are juveniles ( in juvenile plumage) until late the year after the hatch.
(and captive hawks are said to be 1x inter-mewed at this point)

The 1st year birds hatch they don't moult
 
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Cobra said:
Without being pedantic :D
The first moult doesn't happen ( begin) until the following late spring early summer and ends late summer / early autumn
So they are juveniles ( in juvenile plumage) until late the year after the hatch.
(and captive hawks are said to be 1x inter-mewed at this point)

The 1st year birds hatch they don't moult
Click to expand...

This is not what it says in my book (Collins Bird Guide) ....

I quote -

"1st winter - age category usually referring to the plumage following that of the juvenile, usually gained through a partial (in some species complete) moult in late summer/autumn of 1st calendar year, and worn until next moult in spring of second calendar year".

However, I accept that moulting is very complex and that my statement was a generalisation. And that birds of prey and other very large species may be special cases.

But would it be fair to say that for ID purposes you can rule out juvenile plumaged birds of most species after, say, their first autumn? So in early/mid spring there is no way a bird could be correctly identified as a juv?

By late spring (now!) juveniles of early nesting species are beginning to appear, of course.
 
I have moulted out countless falconry hawks so have a fair idea of moulting behavior ;)

The "Collins" I think is miss leading on this point

As I said previously ( lets talk dates as an example)
A hawk chick hatched in May 2008
Will not start moulting until roughly May 2009
It will be in ( once the moult starts ) in partial juvenile plumage
until its completed. late summer 2009.

Agreed, some only partially moult during their first moult
That can be down to a number of factors
"stress" in captivity
or poor food quality / quantity in the wild

Some eagles don't moult into adult plumage for a few years
I believe that the Bateleur takes about 4 years
as does the Bald eagle

I hope that helps to clarify it a little




 
You must have very detailed experience of how hawks moult while in captivity.

However..... as a birder of long experience I have never known any wild bird more than a (very) few months old ever being referred to as "juvenile", even large birds of prey like Golden Eagles. By their first winter, even golden eagles are referred to as "1st-winter" or just plain "immature", I think.

So in a bird ID guide like the Collins one I mentioned, a definition of "juvenile" would refer to almost any bird before its first moult / partial moult, or, in the case of larger birds like raptors and large gulls, a fledged individual in its first summer or autumn -even if it hasn't moulted yet.

I accept that these larger species do not moult in the simplified fashion that I originally suggested. However for the purposes of identifying wild birds in winter or spring, you can effectively discount any illustrations in field guides referring to "juvenile plumages". It makes bird ID that much easier!

they're great pictures of terns, though, aren't they?

jerry.
 
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