April 24, 2015 | David F. Coppedge

Bird Tricks

News about feathered friends and flying wonders, and speculations about how they evolved.

Flight physics: To avoid obstacles in flight, birds need just two postures, the Harvard Gazette says: the wings-overhead stretch, and the wings-tucked in position. This is “why birds don’t crash.” It sounds simple, but when you think how fast a pigeon can fly through jail bars without colliding, as the embedded video shows, it’s pretty nifty. Try getting a quad copter to do that.

Chill out like a bird: Birds show “surprising resilience in the face of natural stresses,” PhysOrg says. The blue-footed boobies in the lead photo know a lot about stress out there on the Galapagos islands. Authors of a new book showed experimental evidence that stressed-out chicks do just fine as adults. It’s not clear what this has to do with Darwin, but one bird evolutionist thinks the study will help reorient research in “a vastly understudied area—the evolutionary interplay between early life conditions and phenotypic plasticity.” Whatever that gobbledygook means, it doesn’t sound like survival of the fittest. It sounds more like Lamarckism.

Amazing FactsWalking on water: You may have seen nature documentaries (as in Winged Migration) where western and Clark’s grebes do their stunning mating dance, leaping from their ducky position to a standing posture then running on top of the water for several seconds. Since they won’t do this in the lab, a Harvard team went to Oregon to figure out how they do it in the wild. Science Magazine says that studies of high-speed films showed “how the birds slap their lobed feet on the water, with all three forward-pointing toes splayed, as fast as 20 steps per second.” This is different from how the basilisk lizard (one of few vertebrates that can run on water) does it, but it is 1/10 the weight. The birds’ foot slapping, however, only accounts for 50% of the lift to keep them elevated, so more work will be needed to figure out the stunt.

The bird bang theory: A biologist from Wake Forest University claims that “evolution is hard at work when it comes to the acrobatic courtship dances of a tropical bird species.” Matthew Fuxjager studies tropical birds named golden-collared manakins. He says, “Our results provide the first evidence that androgenic sensitivity in select parts of the neuro-motor system is an evolved mechanism to facilitate performance abilities and acrobatics in physically elaborate socio-sexual displays.” There are about 60 species of manakins, most that perform a complex dance for mating and rivalry. “The researchers hypothesized that evolution acts to help shape the mating display behavior by controlling androgen sensitivity in the avian wing muscles,” PhysOrg reports. But can testosterone alone account for the complex behaviors? Giving a gymnast a hormone shot will not make him do more complex moves, even if he gets a boost of energy; most likely, upsetting the balance will cause other health problems—possibly cancer. And how does the theory relate to the genetics of the bird? “Our current data support the hypothesis that sexual selection shapes levels of androgen receptors expressed in the forelimb skeletal muscles to help drive the evolution of adaptive motor abilities,” he explains. But again, hormone receptors don’t equate to choreography, any more than more lights create a ballet. Keep the funding coming; “He plans to continue to study how testosterone sensitivity and other aspects of the genetics of muscle physiology have evolved across species to develop these behaviors.”

Feathered friends: Lastly, the University of Chicago provides tips on making your backyard a bird-friendly sanctuary. Advice includes: grow bird-friendly shrubs, install feeders and bird baths, and keep the cat inside.

Adding evolutionary theory to bird watching is like adding an oil slick to a beach. It’s ugly, and it hurts the birds’ image.





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