Friday, April 13, 2012

When good Robins go bad

This is a nice Robin. We like this Robin. It's easily aged as a 2cy by the conspicuous moult limit in the greater coverts: 

This is also a nice Robin:
We like this Robin, too. It can easily be aged as a 3+cy by the uniform olive-tinged greater coverts.

This, however, is a nasty Robin:
It's a 2cy but the moult limit in the greater coverts its subtle — the difference is largely between the overall colour of the feather, the degree of wear, and the quality of the feather. The retained juvenile coverts all but lack a pale tip. Think of this Robin as some chavvy teenage girl who's covered herself in slap and put on a pair of high heels in an effort to look older so she can buy her and her mates a bottle of cider from the local Bargain Booze.

This is also a nasty Robin:
It's a 3+cy; but look at those pale tips to the greater coverts! There's even some fringing to the tips of the tertials — but the overall colour of the greater coverts is still uniform across the feather tract. Think of this Robin as some peroxide-blonde in a boob tube and knee-high leather boots who's off to the Post Office to collect her pension — mutton dressed as 2cy lamb. 

So, as you've probably guessed, this morning was a good morning for Robins. It was a good morning in general — sunny, still, and with 153 birds caught (of which 120 were Robins; full totals online — click Ringing). Making an (overdue) appearance, this male Blackcap:
Our first of the year.

Also another Firecrest ringed; a female — this really isn't doing anything to help me convince people back in the UK that this really is a scarce species in Sweden!

This 2cy male White Wagtail showed a 'classic' 2cy moult with three generations of greater coverts (from innermost to outermost: alternate, formative, juvenile): 

This 2cy male — caught in the same net as the first bird just half an hour later — shows only two generations of greater coverts (alternate; juvenile), thus requires an overall assessment of feather wear for ageing. Even on the closed wing, it's obvious that the older feathers are really quite brown looking:

The difference between the state of this bird's feathers and that of a 3+cy bird becomes even more apparent when we compare it with the 3+cy male from the other week:
With apologies for flip-flopping the photo orientations.

This male Starling shows what is probably about the maximum extent of pale in the iris for that sex. It also shows a rather dull blueish (almost pinkish) bill base.
Compare with the female yesterday and the other males from last week.

This 3+cy Common Chiffchaff carrying a Norwegian ring was a pleasant mid-morning surprise:
Note the lovely fresh primaries; a useful characteristic for ageing in the field...

Finally, what blog post would be complete without at least one Dunnock wing? This strikingly (atypically) fresh-looking bird wasn't — despite the condition of the feathers — too hard to age as a 2cy. In addition to the monster spots of both the inner and outer web of the greater coverts, the fawn-brown fringed primary coverts are also indicative of a young bird; adults tend to show greyer almost silvery edges.

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