Saturday, July 17, 2010

Hummingbirds Hows

How does a bird weighing 3-4 grams (1/10 of an ounce) manage to fly across the Gulf of Mexico twice a year in an 18-20 hour trip and still live 9 years or more?  Who knows?  That is just one of the many "how" questions associated with hummers.
They make their spring trip in late February to early March, and arrive in St. Louis by April 20th, somewhat slower but more predictable than Amtrak.  Needless to say, they are famished.  Refueling at feeders is helpful at that time as many flowers are not yet in bloom.  Feeders should be cleaned and refilled every 3-5 days (4 parts water, 1 part sugar.)  Having multiple feeders will reduce the combative competition of these territorial tigers who will even drive away their babies after a few weeks.
Next comes family matters.  How do they mate?  Wikipedia describes courtship like this.
Males court females that enter their territory by performing courtship displays. They perform a “dive display” rising 8–10 feet above and 5–6 feet to each side of the female. If the female perches, the male begins flying in very rapid horizontal arcs less than 0.5 m in front of her. The male's wings may beat up to 200 times per second during these displays. (The normal speed is 55-75 beats per second).
If the female is receptive to the male, she may give a call and assume a solicitous posture with her tail feathers cocked and her wings drooped. Preceding copulation, male and female face each other, alternately ascend about 10 feet and descend, eventually dropping to the ground and copulating.[4]
We have sometimes witnessed a male afterward doing a short encore of his arcing display, possibly saying "Thanks for the memories."  But then he is out of her life.  Soon there are two eggs which she will incubate by herself for 12-16 days, then babies to feed every 1 to 3 hours.  They require insects for protein, meaning she must catch them on the fly, even stealing some bugs from spider nests.  She continues to feed her chicks for 10 days after they fledge.  It is no wonder that while the chicks may now weigh up to 4.5 grams, she drops to 2.5 grams!
And she raises 2-3 broods a year.  You would think she would say "Not today, I have a headache."
How can a hummingbird possibly fly backwards?  According to wiki.answers.com
A hummingbird can rotate each of its wings in a circle, allowing them to be the only bird which can fly forwards, backwards, up, down, sideways or sit in sheer space. To hover, hummingbirds move their wings forward and backward in a repeated figure eight, much like the arms of a swimmer treading water. Hummingbirds can move instantaneously in any direction, start from its perch at full speed, and doesn't necessarily slow up to land. Hummingbirds can even fly short distances upside down, a trick rollover they employ when being attacked by another bird.
Fantastic Facts:
  • Wings beat 55-75 beats /second
  • Average speed 30 mph, dives up to 63 mph
  • Heart rate 250/min resting, 1200/min while feeding
  • Eat like a bird?  If you eat like a hummingbird, you would take in 30,000 calories a day.
Even hummingbirds have predators.  Hawks, frogs and spiders are a few of the natural ones.  Humans have contributed with feral cats and praying mantis.  While our native mantids are smaller, the large Chinese mantid, (Tenodera aridifolia sinensis) that have been imported by some gardeners to deal with other pests are quite capable of capturing and eating hummingbirds.*  There are videos like this which show it graphically.

At the Bill Roston Butterfly House, visitors will get excited watching a "tiny little hummingbird."  Then they may notice the black antennae.  Whoops!  This is the Clearwing Hummingbird Moth, as shown in a photograph by my friend Dr. Joe Motto.  They indeed hover like a hummingbird while feeding on nectar and can also fly backward as seen in this video of a clearwing hummingbird moth feeding.
Other animals that can fly hover and fly backwards are dragonflies, other sphinx moths, bee flies, and flower flies. 
* Picture from Stan Taylor Blog.

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