Tuesday, April 03, 2012

Great expectations

Conditions this morning were near-perfect for ringing: overcast but not too cloudy, still, and (relatively) warm. It was therefore something of a disappointment that we averaged one bird per net round (totals online here — click Ringing)... and, with seven of us at the lighthouse this morning, that equated to one bird per person! Nevertheless, we did catch a couple of interesting birds.

This Dunnock — a 2cy — was aged using the usual features; but it also showed an additional feature that was of interest.

Check out the fault bars, especially obvious across the coverts but also visible on some of the primaries, secondaries and tertials.

Fault bars form on growing feathers during periods of poor feeding etc. In adult birds, feathers are grown a few at a time, thus neighbouring feathers are usually at different stages of growth at any given time. However, on a nestling the feathers grow all at once and thus are all (in a given feather tract, at least) at the same stage of growth at any given time — hence a period of poor feeding will result in a fault bar at the same position on each feather and these fault bars will produce one continuous line across the wing, as in this Dunnock.

We also caught two 2cy Chiffchaffs. One was encrusted with pollen on the face — a sure sign that this bird has flown in from more southerly climes!

The bird showed a nice pattern of moult in the wing: the outer four greater coverts were juvenile; GC5-7 were formative (post-juvenile); and 8-10 looked to be alternate (pre-breeding). The bird had also moulted T2 during its pre-alternate moult; T1 and T3 were probably formative.

Despite the lack of birds in the lighthouse garden (the only other bird of interest was a female Bullfinch that passed through), the calm conditions allowed for some good seawatching. Two Red-necked Grebes, five Black-throated Divers, one Great Crested Grebe, Common Scoter, Common Eider and Red-breasted Merganser. I've put together a brief collection of extremely dodgy iPhone-scoped footage.

A Hen Harrier flew by but it was practically in Denmark by the time I managed to get a photo of it.

Foteviken this afternoon was quite quiet with a handful of ducks and Dunlin. And a White Wagtail trapped in one of the small summerhouses along the shore, which we promptly rescued — though how it got in there in the first place is a complete mystery. In there paddock my the road there were a couple of Jackdaws, allowing for slightly closer views than the birds the other day.

The bird on the right (bird 1) shows a diffuse though still fairly obvious pale collar and relatively dark underparts; in contract, bird 2 shows no pale collar at all but much paler underparts. It seems that birds like bird 2 are actually quite common; birds with collars like bird 1 seem to account for about half of the birds I've seen — though I still want to check through a large flock to check out the variation.

Here's a closer shot of bird 1:

And bird 2:

In many ways, birds like bird 2 seem to me more striking (in terms of thinking about picking out a vagrant bird in the British Isles) than birds like bird 1... but would the lack of a pale collar mean any thoughts of monedula would be pooh-poohed in the UK despite the strikingly pale nape and grey underparts?

And finally, *live update* — an Osprey has just flown past my bedroom wind. Nice.

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