Saturday, 7 November 2015

A Tricky Siskin

I caught a couple of Siskin at the beginning of the week, which was really nice as I don't handle many of these at all.  Mind you there were a flock of 40+ hanging around one of my mist nets so I was expecting a few more to be honest.

The first bird, a female, was very easy to age as a bird born this year (age code 3)...

Siskin head (3f)

The standard open wing shot

The eagle eyed will notice in the above photo the difference between the unmoulted juvenile-type feathers and the moulted adult-type feathers.  The tertials show it really well (the three large feathers in a line closest to the birds body). The lower of the three tertials has not been replaced and due to its brown-ish cast can be aged as a juvenile feather, whereas the two smaller ones above are blacker, these have been moulted and are now adult-type feathers.  There's also a nice contrast between the moulted adult and two unmoulted juvenile greater coverts...

Greater coverts are always moulted from in to out in passerines, hence why whenever any aren't moulted it's always the outer most one(s).

Then there's the male. When I took it out of the net I thought it was going to be a young bird because it just didn't look like an adult male, but on ringing it I tentatively put it down as an adult (age code 4). However I was never happy with this as I know young Siskins can do very odd and extensive moults (sometimes even complete moults!) and looking at the photos it's gone back to being a young bird (age code 3) again. Here's why...

A nice male Siskin

It had an adult tail (rounded and all feathers similarly worn) and all greater coverts and tertials were adult-type feathers. But what gave it away for me was the longest alula feather...

Virtually the same pic but with numbers

Basically this young bird has moulted everything apart from its primaries (3), primary coverts (2), secondaries (4) and longest alula feather (1). You can tell this by the duller and slightly browner appearance of these juvenile feathers, compared with the blacker tertials (5) and greater coverts (6).  Also in an adult Siskin the wing flash across the primaries and secondaries is deeper yellow, as you can see in this bird it is pale yellow. 

I really love educational birds like this, and hope at least one person finds this post helpful/useful/educational.

4 comments:

  1. Great explanation, Steve, and very interesting!

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    1. Hi Lucy, thanks for your kind comments. The closer you look at birds and wildlife the more there is to learn...

      All the best, Steve

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  2. Steve, this kind of thing is always interesting - keep it going!

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    1. Cheers Tim, I intend too. Thanks very much for your comment.

      See you soon, Steve

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