Sunday, February 7, 2010

The Call of the Wild -- Hummingbird Style

Hummingbirds are regular denizens of our backyard habitat. I believe they are the local non-migrating Anna's variety, but I've never gotten a close look at any of them. All I ever see is a tiny silhouette at the highest tip of a plum branch or a blur and a buzz which is gone before it fully registers on the senses. (No birds are present in the photo above, it merely shows where they like to perch.)

Sometimes I can catch a fuller glimpse when one of them hovers for a moment at the salvia or hollyhock blossoms. For a second or two, the blur takes on wings and a beak and flashing color. Only Emily Dickinson could capture the fusion of motion and brilliance: "A Resonance of Emerald, A Rush of Cochineal." But these glimpses are not enough to see markings and to differentiate between Anna's or Allens, or whatever other type they might be.

I've often seen the mating ritual: the female is a tiny silhouette perched in a tree; the male is a blur, soaring high until he is swallowed up by the sky, plunging straight down in a dare-devil dive punctuated by a loud chirp as he pulls up and flies straight past the reviewing perch where his lady sits. I saw this display last week and added it to my mental list of "signs of spring."

Today -- a spectacular spring day, by the way, a true harbinger -- I was out in the backyard as any sane person would be. The task at hand was to lay down old newspapers on the paths to try and hold back the wild growth of weeds until I can cover them with leaves or wood chips. (A stack of newspapers near the compost bins comes in handy for this and many other uses.) While shingling soaked, muddy, moldy rectangles of newsprint over the burgeoning hensbit and mallow I noticed an article: "Secret of How Hummingbirds Chirp."

It was the front page of the San Francisco Chronicle from two years ago, almost to the day: February 8, 2008. Nothing for it but to enjoy this bit of serendipity, sit down on the bench, and try to read the damp prose enlivened by bits of mud and white threads of fungi.

Two UC Berkeley researchers studying the Anna's hummingbird had discovered that the chirp punctuating the male hummingbird's spectacular aerial display is not actually a chirp. The sound is made by air rushing through tail feathers. "High-speed video, at 500 frames per second, showed that the birds started their dives with their tails shut and suddenly spread them at the bottom, for one-twentieth of a second -- quicker than a blinking eye," wrote Patricia Yollin. This quick motion creates a musical note as the wind causes the inside edges of the ten splayed out tail feathers to vibrate like the reed of a clarinet.

There was lots of other lore about Anna's hummingbirds in the article, some of which surprised me as much as the tail feather news. It wasn't surprising that the male bird soars 100 feet or more and descends at 50 miles per hour. However, I was very surprised to learn that the mating season is November to May! So much for the sign-of-spring idea. Those mating flights must be going on right through the winter. Why have I never noticed them except when I expect to see them?

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