Ah, the life of birds.

Specifically, the sex life of birds.

In years past, I often used this line in these columns: Birds are just like people. Used it too often for the Muse. But, they are in some ways. They flirt and eye each other. They commit adultery. Some are homosexual. Just as people do, can and are.

Now comes bird porn.

Well, sort of. Now comes a revelation into what turns American goldfinches on — a loose definition of pornography, I reckon.

In a devilish experiment devised by a master’s student, Thomas Luloff took a bunch of captive American goldfinches and divided them, putting half in a cold room, half in a warm room. The cold room simulated spring conditions, the warm room summer.

The goldfinches in each room were isolated into these groups and presented with different visual clues. They could see a thistle in bloom, a nonblooming thistle, or, as a control, no thistle at all.

It is known American goldfinches begin their breeding late in summer when temperatures are seasonally high and when thistle species are flowering. Thistle seeds are prime food sources for young goldfinches and so are critical to this songbird’s reproduction.

So — how does one judge if a bird can be, well, photostimulated? Briefly, a human measures any changes in testes size and changes in the concentration of testosterone in the male or another hormone in the female. Enuff said. Presumably, the birds already know.

Fiendish experiment results: (1) There was no response to the sight of thistles by any birds kept in the cold room. (2) There was a significant effect at the sight of blooming thistles in the warm room. Birds exposed to the sight of a blooming thistle responded more sexually than to a nonblooming thistle. The control group showed no change.

Now, there’s a serious side to this study. As the planet warms, a lot of birds, especially migrant species, may not initiate breeding at the peak times for the foods they must have. What will that mean? Poor reproduction, starving young, no second broods in those birds that otherwise second nest.

I’m indebted to Dr. Heather E. Watts of Loyola Marymount University, Los Angeles, for the information I’ve used here. Heather has noted that the idea of a visual clue isn’t novel. A 2000 study of antbirds found that the sight of desirable live crickets affected male antbirds’ physiology and increased their singing. Ants are dandy, but crickets are quicker.

Visual clues. Photostimulation. I know it when I see it.

Field Notes: A question frequently asked at this time of the year is: Where did all the birds go? My bird feeders are full, but nobody comes. What happened to my birds?

I don’t know. Obviously, the birds are after some prey items they need at this season. What can be more nutritious than sunflower or niger seed? Has to be insects, mostly, I assume. The abrupt absence of birds is a bit unsettling to devoted feeder watchers, whatever the mystery is.

A male osprey outfitted last year with a radio transmitter migrated from Jackson Lake in Grand Teton National Park to Cuba to overwinter. He has done it again, following much the identical route, one he pretty much reversed this past spring. A juvenile osprey flew to the Texas coast and is still there. Another collared adult went to Mexico and returned to Grand Teton.

This summer, another male osprey and two of his young were collared. One juvenile started to migrate Sept. 22. As of that date, the adult and the other young osprey were still along Jackson Lake.

On Sunday, Debra Patla found 22 American pipits on the National Elk Refuge; surely a migrating flock. Deb’s sister, Susan, noted a large pipit concentration near Pinedale on Saturday. Deb was impressed by vocalization from chorus frogs and by seeing spotted frogs and toads on a late September date.

A splendid color season is lingering. Long may it last.

The Jackson Hole Bird Club will meet at 7:30 p.m. Sunday in Jackson Town Hall. Wildlife observations, socializing, refreshments and information exchange. Amy Courtemarch, habitat biologist with the Wyoming Game and Fish Department, will talk on her research into bighorn sheep in the Teton Mountains. Everyone is welcome to attend. Free.

© Bert Raynes 2011

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Bert Raynes writes weekly on whatever suits his fancy with a dash of news on nature and its many ways.

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