Ups and downs

 Our last 2 sessions at Belvide were pretty good with 80 to 90 birds, so we were looking forward to today's session ( moved to Tuesday because of poor forecast for Wednesday)--especially since reports from around the country suggested that migration is well under way. Unfortunately, the vagaries of bird movements dictated that we ringed only 54 new birds today. As ever, we have a book of excuses to refer to, and we're pretty sure why the catch was lower than we hoped. The rain started early evening on Monday, stayed until dusk ( when birds are preparing to migrate), and was intermittent most of the night. Resulting in fewer migrants for us to catch.

However, fewer birds does give us more time to provide instruction to our trainees. Here's just a couple of the things we looked at this morning.

First, all juvenile Blackcaps leave the nest with brown caps. Over the few weeks after fledging, all these birds moult out their cap feathers. Females moult in brown feathers, and of course, males moult in black feathers.

This is clearly a young male with about half of the  black cap feathers moulted in.

Second, the STRUCTURE of primary flight feathers is instructive in a few species--but perhaps no more so than in our ability to separate Willow Warblers from Chiffchaffs. I hope the next 2 pics will illustrate this...

I have numbered the ( very short) first primary, and the sixth primary. If you look carefully at the outer web of the sixth primary, the arrow shows that is is the same width right to the tip of the feather. In contrast look at this Chiffchaff wing....

You can see that the outer web of primary 6 narrows down for the last quarter of the feather. This is called an ''emargination'' and if present on P6, it gives a cast iron ID that you have a Chiffchaff. Great in the hand--but not much use in the field!!

What will Saturday bring---apart from more rain!!??