I’ve always loved the story of Agassi and the fish, where a prospective student of his has his powers of observations tested by a dead and rotting fish.
Having been an avid observer of birds of over the years, I was blown away by the amount of what I did not know about birds. David Lukas’ lecture explored the bird from the inside out, exposing a lot of the critical tweaks of evolution that allows it to do its most arguably bird-like activity: fly.
With a overhead projector, transparencies, and a dry erase pen, David lead us on this exploration — starting from what we in the audience knew of what makes a bird a bird. A lot of what has driven bird evolution is around the ability to fly: reducing weight, balance, and increasing power.
Power is most obvious in its muscles — a birds breasts muscles are around 30% of the birds overall weight.
Reducing weight has led to hollow bones, a lack of teeth, gizzards in the middle of the body at the bird’s pivot point where their food is ground up. They have a fast metabolism which processes food in 15 minutes, and dispose of waste as uric acid which doesn’t require a bladder.
The bird jaw and feet have mechanical mechanisms for serving the bird’s needs. In opening the beak — the upper beak is pushed open when the lower beak is pulled down. This limits the number of muscles needed for the bird because muscles = weight. The action of sitting, folding the legs, curls the toes of the bird — this is what allows the bird to sit overnight on a branch without sweating it. Some raptors take advantage of this when they take down prey, they’ll land and seem to smother their prey — what their doing is taking advantage of this mechanical action to add a killing below to their strike, closing their talons just in the act of landing.
The ribs — which are small jointed fragile bones — act as a bellows for the bird, pumping air through the body. Some of the birds hollow bones (which in general are not all that fragile) also play a part in the bird’s respiratory system, helping in the transport of the air between throat, air sacs (front and back), and then out again. This one way path of the air also helps in keeping the bird cool (birds run hot!), acting as a heat exchange throughout the body. Everything is built for maximum efficiency.
Wings and feathers are whole other pack of fascinating details from the way feathers grow and overlap and have different functions: down for insulation, feathers for flight (and also a degree of waterproofing with their overlapping and interlocking barbs and barbules), and little filoplumes sticking out through the other layers of feathers to provide some additional sensory inputs to the bird. David have the image of someone dressed in a down coat with a Gortex jacket worn on top — they would not otherwise be able to feel the air.
A surprising little detail of feathers though is that feathers appear in groups, with most on the head. The body itself is mostly bald with feathers combed over to cover it.
There seemed to be no end to the surprises from their huge eyeballs, to their tips of their tails, all these little details that make birds what they are — another lesson in how little I know about the world, and how fun it is to learn.
You can find out more about David Lukas, his books, and upcoming presentations on his website lukasguides.com.
SF Natural History Series 