The monarch butterflies float south in the fall in order to winter in the mountains of Mexico and parts of California. What impulse starts a monarch on its journey? What keeps it aloft for thousands of miles instead of gliding down for a rest in a juniper, feeling that this flight is too much adventure for one butterfly? And though millions migrate each year, and will overnight clustered together in trees or on boulders for warmth, the monarchs don't travel together in the way cranes and geese do. Instead it seems one by one they pick up, gain quite a bit of altitude, and try to ride a norther across the border.

Thousands of individual impulses to fly cross continent.

The monarchs show up right about this week each year in central Texas, some from as far north as Canada. No individual butterfly makes the whole trip there and back; each migration marks a span of three or four generations of butterfly. So how do they know not only when, but where to go? They find the same overwintering spots even though not a single one has been there before. 'Somehow they know their way, even though the butterflies returning to Mexico or California each fall are the great-great-grandchildren of the butterflies that left the previous spring.'
(monarchwatch.org)

If you recline on your back and look up to a clear blue sky, you’ll see the tiny silhouettes far overhead, floating, each one a weightless wonder, an awesome traveller.