Saturday, 24 October 2015

Fieldfare Revisited

Seeing as the Fieldfare I caught at Beer Head yesterday was the first Fieldfare I've caught as a C ringer, I thought it deserved a bit more attention on the blog.  They do seem to be pretty mist net-savvy birds, unlike the smaller species of thrush that are caught much easier.

Such a smart bird

I thought I'd go through how we came to age and sex this bird in some detail.  I have to be honest and say as I've handled so few Fieldfare I'd forgotten you could sex them, but a quick look at the ringers bible, Svensson, revealed that a closer look at the crown feathers should tell all...

And here's our bird...

What do you think?

Look particularly at the feather showing the largest amount of black towards the top of the pic, the black shows a concaved shape as it runs up the spine of the feather, matching Svensson's female example nicely.  So a girl it is.

Then there's the ageing, and I have to say I had a feeling it was a bird born this year (age code 3) as it came out of the net, because overall for a Fieldfare it just looked a bit dull.  I can't believe I've called a bird this stunning dull, but adults have a lovely rich chestnut brown mantle and scaps and lead grey head and rump - not this one though.  

The photo is pretty poor quality I'm afraid but it was pre-sunrise!

I've marked where the moult limit is, between the brown inner replaced adult-type greater coverts, and the old juvenile ones.  As well as the colour difference, you can see the difference in wear between the two, with the old juvenile coverts looking pretty knackered, whereas the adult ones are much smoother edged. That's simply because the juvenile feathers are probably three or four months old, but the new replaced adult ones a month old at most. 

And as with most birds, the tail is usually pretty helpful too when it comes to ageing...

I always find it hard to spread a tail nicely for photographs

Again look at the wear, if this was an adults tail it would be a month or so old as the bird would have undergone a complete moult before autumn migration - but it is pretty ragged and worn.  I'm sure other 3's show pointier tails than this, but I've found tail shape can vary a lot between individuals even if they are the same age and sex  The colour of the feathers, dull brownish grey, also fits with the bird being a young female, adult males have jet black tails.

Hope you've enjoyed this post, it's nice to get a bit technical now and then.  I'll finish it with a quick snap I took of a couple of Reed Buntings that I caught at Lower Bruckland Ponds earlier in the week, they were both 3's and conveniently one of each sex...

If only I had a third hand I could have got many more photos!

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