A school of blackbirds

One of my favorite  sights is the crazy blackbird flight school offered each Spring as hundreds or thousands of birds launch into flight together, wheeling and turning in unison.  We have a very healthy stand of bamboo grown from a few starts given to us 20 odd years ago by our friend Joe.  That little patch has grown into a dense grove that now provides shelter for hundreds of birds all winter.

frosty bambooHopefully the bamboo has survived this particularly brutal winter.  As Spring approaches, the bamboo residents are becoming more and more noisy.  At night I think there’s a windstorm raging and realize it’s the birds rolling over in their sleep in unison. In the morning and evening they put on an airshow going about their business.  I believe these are mostly red wing blackbirds, since I hear their territory calls coming from the bamboo, but apparently flocks often contain starlings and other blackbirds as well.

There are two groups to begin with; they seem to coalesce into one, but then split again, with one group settling into roost.  It would be interesting to know, but I can’t tell from the video,  if the  group that peals off to roost first is made largely of members of one of the two original groups.

Flocking is mesmerizing to watch.. It was modeled in a classic artificial life routine called Boids by Craig Reynolds.  His flocking model defines only 3 steering behaviors:  “Separation –  steer to avoid crowding local flockmates; alignment – steer towards the average heading of local flockmates; and cohesion – steer to move toward the average position of local flockmates.. … Flocking is a particularly evocative example of emergence: where complex global behavior can arise from the interaction of simple local rules.”