Flocking Science

Check out the beautiful video below of a “murmuration” (flock) of starlings acting in hypnotic unison:

Now, if you spend all day thinking about how to model biological systems (who doesn’t?), you might see that video and wonder about the rules each bird must follow to allow such spectacular emergent dynamics. Every individual bird probably gets some simple cues (direction, speed) from its neighbors, who get some from their neighbors (and that first bird), etc etc, and when these simple cues are acted upon and combined together all the birds form a giant complex morphing swarm.

A quick search reveals that the starling dynamics, and swarming behavior in general, have been the focus of a considerable amount of research and modeling. I’ll link this PLoS ONE paper since it’s open access (meaning everyone can view it in its entirety for free) and has some really cool videos showing off the modeling endeavors of the authors. In their simulation, each individual is characterized by parameters like mass, speed, position, and orientation- and these parameters get updated based on interactions with other individuals within a certain neighborhood. Just like in real life, these simple interactions scale up to show a swarm of individuals that behave as a complex, yet unified, group. (check out the videos in the link!)

I’ll also share this PLoS Computational Biology paper (also open access) which explores why individual starlings pay attention and respond to exactly seven of their neighbors (the authors report the number is special because it optimizes the balance between group cohesiveness and individual effort).

Another side effect of thinking about biology all day is always having to ask “Why (and how) did this evolve?” That is, what benefit does this intricate dance give the birds that allowed it to selected for and maintained? Being relatively ignorant of birds and their behaviors, it seems that such a show would turn into a buffet for predators. Well, maybe not. Here is a video of a Peregrine Falcon trying to snatch a starling during the flocking behavior and continually coming up empty handed (clawed?). The Peregrine Falcon is the fastest member of the animal kingdom, reaching diving speeds of over 200mph, so maybe this dizzying behavior is a great way to confuse even the quickest of predators.

I’m sure there is more to it than just predator avoidance, so feel free to add your 2 cents below!

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