Thursday, April 26, 2012

WHAT'S NOT TO LIKE ABOUT A LEK


Netta Smith and I made a very long trip just to see a bunch of chickens strutting around. But these were special "chickens," and it was worth the trip. We drove from Seattle all the way to Dubois, Idaho, where we had reserved a blind in mid April at the edge of a Greater Sage-Grouse lek. This species, Centrocercus urophasianus, is the largest North American grouse. The males are not turkey size, but at over three kilograms in weight, they are big chickens!

Males begin to assemble at display grounds, which are called leks, in early spring, often while snow is still on the ground. Then they may display for as long as three months. The leks can contain just a few males or rarely up to several hundred. Males arrive at dusk and may remain through the night, but highest activity is usually around sunrise. When fully into it, males perform their complicated display 6-10 times/minute. Males keep the tail erect and fanned at all times, but then at intervals they step forward and inflate their large esophageal pouches.

The pouches swell and protrude through the snow-white neck feathers and the whole neck and breast move up and down together with the wings rotating forward and back. The expanded sacs make loud plops, and these sounds dominate the auditory experience at a lek, although the loud songs of meadowlarks often add to it. The males also make a swishing noise with their wings and a rattle with their tail feathers, an impressive collection of nonvocal sounds.

The smaller, duller females are not much in evidence, but they move quietly through the lek, apparently looking for a male that impresses them. If they find him (it may take several visits), they crouch down and copulation takes place. Some males are outrageously successful, very few individuals accounting for most of the matings that take place on the lek. We don't know exactly what gives them that advantage, but it may be that some males never get to mate!


At the Dubois lek, there were over 50 males at sunrise. A fly-by Prairie Falcon scared about half of them away with a sudden burst of flights in all direction. Another bunch left a bit later, and the few females present left at that point, but a dozen males stayed behind and displayed for another hour after the sunlight hit them. The closest were 30 feet from the blind and were wonderfully oblivious to the telephoto lenses poking out at them and the constant click of shutters.

After the female copulates once, she has sufficient sperm to fertilize her clutch of about eight eggs. She wanders back into the sagebrush and builds a nest, often under a shrub, incubating the eggs and then shepherding the young around as they grow. Males take no part whatsoever in parental care, quite typical of grouse.

The last few birds flew away from our lek about two hours after we arrived, leaving us with a feeling of awe at how natural selection had molded such showy, yet precise and stereotyped, behavior the sole purpose of which was to gain a mating opportunity.

The town of Dubois puts on a bird festival every spring, Dubois Grouse Days. Check their website for next year's show. Reserve a blind for yourself. You don't have to be a photographer to appreciate the spectacle, but I would advise bringing a camera!

Dennis Paulson

No comments: