Marc Brunet Jul 6, 2015:

Very interesting! It's in your web link, but I did not pick up the sense of it until you supplied an example of it here. (No wonder, I had read it as かっこう！） And the embedded quotation marks :『...』? (Oh, the input software just gave it to me: 二重かぎかっこ; and all up, excluding math symbols, you have 5 more varieties of bracket pair-type punctuation marks than we have, each with its own name. Well, thank you indeed for everything!

Port City Jul 6, 2015:

The kanji 鉤 is quite often replaced with 鍵, probably because the latter is a more widely used kanji. The punctuation mark「...」is called 鉤括弧（かぎかっこ）. You would know why.

Marc Brunet Jul 5, 2015:

So this 鍵 was in fact a typing oversight for 鉤 , then -- one which a native reader can quickly rectify from the context, as we do with misused homonyms when they crop up.
Thank you for your help, Port City! :-)

Port City Jul 5, 2015:

鍵 here doesn't mean a key or a lock. It refers to a 「先の曲がった金属製の器具」, which can be V-shaped. (That means we don't have any head start.)
https://kotobank.jp/word/鉤-459541

Marc Brunet Jul 4, 2015:

fascinating research results... but... Question: .. How to make sense of 鍵になって as the Japanese view this behaviour?
as an abstract pointer to a clever 'lesser effort' solution, or to how each bird in that formation sets a flapping 'phase' that determines the offset by which its immediate follower chooses to set its own for best advantage?
If so, our Japanese friends seem to have had an intuitive head start on what was going on, compared to us who only stated the obvious: just the shape of that formation and nothing more...
But is that the case or is that expression actually referring to something else?
Would love to hear their final word on this point... and so thank you for your help, dear native colleagues :-)