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Saturday, September 22, 2012

Why don't birds fall off their perches?

Belted Kingfisher
When birds sleep or rest, they may perch on a branch and remain there, motionless, for a long time. But, even in sleep, they won't lose their grip and fall off.

You see, their legs are not constructed the same as ours. The arrangement of the leg bones, muscles, tendons and feet is roughly opposite of ours, having sort of a ratchet-type operation. When awake, birds can adjust the leg/foot movement, but when asleep the feet clench tightly, like they're glued to the perch. This happens automatically.

Scissor-tailed Flycatcher

All fall migration flights aren't to the south. Actually, most north Texas birds don't migrate at all. The Grey Bat, however, is a tiny harmless creature that flies north. It lives in warm, dark caves, like south Texas and Florida. But when it wants a place to hibernate each winter, it seeks out relatively cooler areas, perhaps Arkansas or Tennessee.

During this wintertime hibernation in cool areas, its heart rate drops from several hundred beats per minute to twenty or thirty.


Wednesday, September 19, 2012

You have bats in your neighborhood. Really!!!

Whether you've seen them or not, it's almost certain that bats are in your neighborhood. Which is a very good thing, despite what old Hollywood fables proclaimed.

Mexican Freetail Bat
One healthy adult bat can catch and eat about 5000 flying insects per night. Pretty good for an animal about an inch-and-half long. We were just in Austin, and visited their urban bat colony; didn't see a single mosquito.

Bats hunt within a radius of about 40 miles. So a bat roosting in your neighborhood could be eating mosquitoes in Gainesville, Frisco, Graham or your back yard.

Actually bats are not rabies vectors. They don't carry rabies without getting very sick themselves. And if they're sick they can't fly or hunt food, and usually die in about a day.  Not much time to bite a human and transmit rabies. There is no plausible evidence of airborne rabies transmission by bats. To the contrary, they eat a lot of insects that do carry disease - like West Nile Virus.

Yes, bats have an image problem. If a colony of bats gets wiped out (for whatever reason) it's slow to repopulate. That's because each female has only one "pup" per year.

Bats like to be near water. That's because one can lose up to half its body weight through evaporation in a day. A dangerously dehydrated bat isn't able to catch many insects - if it's a female, she and her pups may die.

Austin's bats generate roughly $10-million a year. Does your neighborhood or city have a potential place for a bat colony? Bridge, tunnel, old overpass? Now's the time to start planning for next year.

     You may have noticed lots of activity at Hummingbird feeders too!  There's a lot more eating and sharing and a lot less fighting. It's working together toward the common goal of a successful migratory flight around the end of the month.  (maybe humans could learn something from this behavior)

Sunday, September 16, 2012

The only bird here that does a good job of smelling

Turkey Vulture
Almost all birds have a very weak or no sense of smell. The one exception in north Texas is the Turkey Vulture. Through evolution it developed a good sense of smell in order to survive.

Turkey Vulture
The Turkey Vulture's purpose in life is to get rid of carcasses (roadkill, dead animals etc.)    It locates them by smell. Turkey Vultures are so good it that they can locate leaks in natural gas lines (The chemical mercaptan, added to gas, smells similar to rotting flesh). By the way, no kind of vulture has ever been known to attack or kill a healthy animal.

Another evolutionary modification helps it pick apart dead animals. It developed its featherless, macabre-looking, head and neck so it could probe into rotting carcasses without picking up bits of flesh and blood.

 Birds here talk Texan.   In a 'birdy' way.   Identical kinds of birds often sing differently, depending on where they were raised.  For instance a Blue Jay here in north Texas sounds a bit different from one (for instance) from Connecticut.