Laughing Gulls in flight
Everything about avian morphology has been shaped by the requirements of flight. Flight is hard. Animals are heavy, being largely composed of water, and air is not dense; you have to work hard to generate any force by manipulating air. The problem for any flying animal is to be light yet powerful – and to still be a viable animal, capable of eating and storing energy and making babies. A hypothetical weak but extremely light animal – think an air-jellyfish – might be able to fly, but would probably starve. While the ocean is filled with floating particles that real jellyfish can catch simply by passively floating, the air is not so bountiful. (You could argue that web spiders filter-feed in air, but… all right, I don’t know if air-jellyfish are impossible. I think we’re getting off-topic here.)
Air-jellyfish wafting through a pink sunset.
(Or, Northeast Pacific sea nettle in an artistically-lit tank at the Shedd Aquarium.)
In any case, birds didn’t start out as light, thin, filmy creatures. They started out as small raptor-y dinosaurs. Natural selection acts only on the traits that are present: massive change to the shape of an organism is hard. (Not impossible! But comparatively rarer.) Birds started out with backbones, four limbs, a head, two eyes, etc., and they evolved flight from that initial morphology.
But how do you make a dinosaur that can fly? Dinosaurs are strong, yes, but they are heavy. Bones are heavy; muscle is heavy; fat is heavy; teeth are heavy.
The birds of paradise have been getting a lot of attention lately for the elaborate courtship dances of their males, and nobody is going to argue that they don’t deserve it. But it isn’t all “males dance, females judge” in the avian world. The displays of male birds of paradise reflect high reproductive skew: a few males mate a lot, a lot of males never mate. It’s worth it to the males to devote incredible amounts of energy and resources to attracting females, because if they’re successful, they may sire many chicks. They can afford to spend all that energy and resources on crazy feathers and tricky dance moves because that’s all they have to do, parent-wise: they don’t help females build the nest or incubate the egg or raise the chicks.
Male Greater Bird-of-paradise. Photo by Ivan Teage.
But birds are diverse; the birds of paradise reflect just one point on a spectrum of mating systems. Near the other end are birds with low reproductive skew. Males of these species look pretty much like the females, and they contribute about equally to parental duties. You might expect that these species would lack dances the same way they lack meter-long curlicue tailfeathers, but some of them have dances every bit as formalized and elaborate as the birds of paradise. The difference is that these dances are duets.
Laysan Albatross pair performing courtship dance. Photo by Michael Lusk.
(Note on videos: I know clicking on videos is annoying. But it’s worth watching the videos in this post, I promise.)
After mentioning my local mutant junco here several times, I figured I owed you a photo, so I went stalking him today. In searching for him I also found lots of normal-looking juncos. I did eventually find my white-splashed bird, so read on to see this unusual junco – after first admiring the regular juncos, because every junco is awesome.
You can walk on glass walls, right?
October, about to jump onto an egg carton
Oh, you say you can’t do that. So how come October can?
Last year, I waited to order color leg bands (for banding the juncos) until spring. This turned out to be a mistake, since everyone else ordered their leg bands at the same time, so all the good colors got backordered and I spent the first half of the field season banding my birds in just orange, lime, green, light blue, brown, and grey. If you’re wondering whether brown or grey bands show up on a junco leg: well, no, they don’t.
I learned my lesson. I’ll have a full arsenal of colors for this field season:
I think this is the least dignified photo of Limpet I have ever taken