Sunday, February 07, 2010

Birds of a feather

I spend a shameful amount of time each day watching the hummingbirds and bananaquits forage at our feeders. The bananaquits can't quite fit their beaks into the hummingbird feeder, with its sugar water, so we put granulated sugar out for them. Still, they feel proprietary about the sugar water and do their best to keep the hummingbirds away. Unsuccessfully, of course. The hummingbirds dart and snitch with a velocity the bananaquits can't match. Beating hearts with feathers.

Lovely thing, the feather! An oar for the air. Featherlight. The association with flight is irresistible. But flight may have been an afterthought. It is now generally agreed that birds descended directly from dinosaurs, and feathers appear to have been a dinosaur feature before birds ever left the ground.

If not for flight, then why did feathers evolve? For insulation, perhaps. Or maybe camouflage. Or -- it is Valentine week, after all -- maybe to attract a mate.

In a recent Nature Online, paleontologists from the University of Bristol in the UK and the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing offer the first evidence for coloration in dinosaurs -- fossilized evidence of pigmented feathers in a dinosaur called Sinosauropteryx. And here they are, in an illustration borrowed from Science, two Sinosauropteryx, with white and chestnut striped tails, doing a mating dance.

Why not more striking colors? Why not a Valentine red, for instance? Natural selection works with what it's got, cobbling together new things from bits and pieces of the old. You like my chestnut striped tail, I'll see if I can make it flashier. You have a taste for sugar, I'll bring you candy.

Cobbling together whatever works, and look! The feathers on my forelimbs help me glide as I lope along the ground, escaping a predator. And look! I take to the air.