Friday, June 01, 2012

Flaming June

Rain, 35 mph winds... welcome to June! At least the temperatures are up (just) above 10 °C.

It was another four bird morning at the lighthouse this morning: one Icterine Warbler, one Chaffinch, and two Common Whitethroats. One of the whitethroats, a 2cy (male?), had done some funky pre-breeding moulting.

 On the right wing it has moulted all three tertials, S5-6 & S1, and P5-10 (but not the primary coverts).

On the left wing it has moulted all three tertials, S4-6, and P1-2, P6-7 & P9-10.

The moult limit on both wings was clearly visible, even on the closed wing. Not surprisingly, the tail was entirely adult-type.

In the afternoon, we ringed a brood of Kestrels in Skanör church before doing the weekly counts at the north end of the peninsula. The weather was foul and we saw very little of note.
Skanör church, built in 12th or 13th Century

Three of the Canada Geese on Knösen showed these odd white faces but otherwise were completely normal; some Barnacle Geese genes from many generations back or some quirky feature in the local population from inbreeding?

Finally, since this has become a hot topic in recent days, here are a few photos of Pied Flycatchers that I never posted at the time. I always cringe slightly every time a male Pied Flycatcher is reported as a "first-summer" — inevitably it's been aged on "the presence of a moult limit in the greater coverts" or "contrast between black and brown plumage". Unfortunately, for species that undergo a partial spring moult (e.g. Pied Flycatchers, pipits, wagtails, Sylvia warblers) the mere presence of a moult limit doesn't prove a lot. It's also worth remembering that a male Pied Flycatcher's winter plumage is basically brown and that the contrast shown in spring between (new) black and (old) brown is not because the brown feathers are black feather that have become bleached/worn, it's because they always have been brown. So, from 29th April, here is a 2cy (first-summer) male:

And a 3+cy (adult) male:

These two individuals show different patterns of brown in the plumage — in the adult it is more concentrated on e.g. the neck, while in the 2cy is is more spread across the mantle. I think I'd be hard pushed to say which had more or less brown in the plumage, though. The adult has undergone a slightly less extensive moult than the 2cy (as seems to be typical in this species), having not moulted e.g. any median coverts. Key to the ageing is the overall colour of the flight feathers. There is still some contrast between the black tail/upper tail coverts/mantle of the adult and the primaries/secondaries/primary coverts, but the latter are rather dark and blackish. On the 2cy, they are considerably browner. The differences are quite obvious on the spread wings:
The 2cy (above) shows less white in the flight feathers than does the adult (below). Note that both birds show an obvious moult limit in the greater coverts — in the adult bird, this contrast is between last year's autumn-moulted "adult winter" plumage and this spring's "adult summer" breeding plumage; on the 2cy, the contrast is between last year's juvenile greater coverts and this spring's "first-summer" breeding plumage. There is a subtle difference between the unmoulted greater coverts; in the adult, the feather is neatly and evenly fringed pale, compared to the 2cy where the juvenile coverts show a distinct pale tip to the coverts (hard to see on this photo).

This is a topic that Fabian Meijer and I have been discussing quite a bit recently; we both have quite a few photos of Pied Flycatchers and we're toying with the idea of writing something a bit more complete on the subject. Watch this space.

No comments: