Waders night&day

2 08 2013

“I might as well open the window and kiss the night air.”

– Franz Kafka

We don’t have too much energy. After almost 2 weeks of ringing, the forces are already scarce since the cruel northern summer forces us to wake up at 3 o’clock in the morning. Therefore, when deciding what to do, you’d rather think twice if it would pay the effort. Moreover, the weather in the last days has not been so pleasant. Scattered showers, wind, foggy dawns… everything leading to an unpredictable and usually poor catch.

I had been told in the spring that this variable weather is good for waders so in the last days we’ve been focused mainly on this. The first night of wader and tern ringing was very productive, with more than 50 birds caught and some interesting species such as a first in-hand species for me: Sandwich tern. With almost no experience with them, the only thing I was able to notice in the field was the presence of “some” moult limits in the primaries. It looked promising and thought it deserved a better look; maybe it was time for me for finally tackling tern moult and ageing!

So, the first bird we caught showed 3 generations of primaries: P1 was growing, P2 was absent, P3-4 were the 2nd newest after P1 and P4-10 were the oldest, showing a decreasing gradient of wear. Both adult and juvenile Sandwich terns undertake a complete moult after breeding season, but juveniles doesn’t start with wing feathers until December, whereas adults start moulting them in July. Juveniles face autumn migration with entirely juvenile primaries, while adults have already moulted some. Both suspend the moult during the actual migration and carry on with it when reaching the wintering grounds. In the following spring, adults are done with the primaries and can afford a pre-nuptial moult that includes a variable number of inner primaries. Juveniles are still busy with their post-juvenile primary moult and don’t undertake any pre-nuptial. And then, what was this bird? After a really interesting discussion with Stephen, everything made sense: P1 belonged to this year post-breeding moult, P3-4 were pre-breeding and the rest of the feathers came from the 2012 post-breeding. Interestingly, the obvious step in wear between P5 and P6 is due to a suspension but not to a different generation of feathers. It’s worth to keep in mind P5 has another migration on its back! The final conclusion was that this bird must be a 3cy+.

Sterna sandvicensis 3+ restricted pre-breeding

The second bird we caught was also a 3cy+, quite similar to the first one, but with a much more extensive pre-nuptial, comprising P1-7. The 2013 post-nuptial moult had not started yet and even the head was in an almost complete nuptial plumage. All these evidences points to the bird being a late breeder: more time for a more extensive pre-breeding and a bit delayed in the post-breeding. The pre-spring migration suspension is probably between P8 and P9, what means the bird being in the wintering grounds until later than the first bird of the night (suspension between P5 and P6).

Sterna sandvicensis 3+

Sterna sandvicensis head

For making things crystal clear, the last Sandwich tern of the night was a 2cy. It showed also 3 generations of feathers but none of them was a pre-nuptial. P1-3 were 2013 post-nuptial but the subsequent primaries were not newer as in the other birds. P4-6 were much worner, what means they should come from 2012 post-juvenile. Surprisingly (or maybe not that so), P7-9 were really fresh, but this fact doesn’t mean they are pre-nuptial, but just the continuation of the post-juvenile. There is therefore a pre-spring migration suspension between P6 and P7. And yeah, as you might have already deduced, P10 is juvenile.

Sterna sandvicensis 2cy

Chapter two: Red knot. The day before yesterday I went to Revlana together with the gangsters trying to see some good stuff. The place was in fact packed with waders and terns. We’ve already seen some juvenile dunlins, but this wave of waders is still conformed by mainly adult birds in stunning summer plumage. I payed especial attention to Red knots, since there was an approachable flock composed by around 10 birds of different levels of plumage brightness. I focused on one of them and saw some really old feathers. Later in the evening, looking at M&P classical reference, we realized 1cy Red knots can moult some inner, some outer or all the primaries during the winter. Therefore, a bird showing a moult limit in the primaries now must be a 2cy but a bird showing a wholly uniform plumage can’t be safely aged as a 3cy+. If you look at the primaries in the picture below, it’s possible to see that the ones conforming the tip of the wing are much worner than the inner ones. Some tertials are also retained.

Calidris canutus2

detail moult red knot

Yesterday evening, encouraged by last night’ success, we came back to Möklappen for another night of wader ringing. This time, the catch was not as good, but a bright Red knot and some interesting Common terns were enough to keep us awake. The terns deserve another post (what are you waiting for, Stephen?) but, to carry on with the Knot thing, the bird we caught showed a moult limit between the pre-nuptial body feathers, scapulars and some coverts and the post-breeding coverts and flight feathers, but not the same moult limit in the primaries as the bird I had seen in the field. It’s interesting to notice how extensive the pre-breeding moult is, much more than any other Calidris species I’ve handled, since it can include even some GCs.  We finally aged it as a 2cy+ keeping in mind some juveniles can undertake a complete post-juvenile in winter. However, the timing in the moult of primaries of juveniles and adults might be different so, in case the rest of the variables were constant, it could be theoretically possible to age them by assessing the wear of these primaries.

Red kot in hand

Red knot wing

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