In Pas De Quatre, La Sylphide, Giselle, this movement transports the ballerinas swiftly across the stage, implying her not-quite-physical but definitely supernatural character.
In the fourth act of Swan Lake, the corps de ballet of Swans are genuinely mourning and almost weeping sometimes, from what seems like an eternity of bourees, as they try to keep the White Swan isolated from Von Rothbart and The Prince.
So what makes this movement effective, and maybe a little easier to do?
Strong core muscles and well held ballet turnout keeps you well in control of your leg movements. In the bouree, the knees are not entirely pulled up, but instantly tensing and releasing, invisibly.
The more turnout you have, the easier it is to keep the back foot leading.
Being pulled up at the bottom of your core muscles allows you to maintain your posture without clenching your gluts, or your butt muscles, too tightly. This is important because it allows a fluid, fast, tiny transfer of tension in the hips, knees and ankles. This is where the fluttering quality comes from.
In contrast, if you are clenching your gluts instead of using your rotator muscles to turn out, you will be tight and rigid, and pushing down into your thighs, instead of pulling up out of them. As well as impeding the movement, this makes your thighs look bulky, instead of long and lean.
So to re-cap:
strong core muscles = fluid movement in the legs
strong core muscles = relaxed neck and shoulders
strong core muscles + proper turnout = the correct tension in the hips and thighs
Mentally, picture the movement of picking the toes up from the floor, not putting them down. It can trick you into feeling light and floaty.
If you found this helpful, there are many more tips in The Perfect Pointe Book.
Enjoy these bourees - The Dying Swan