More Than Meets The Eye At Mating Ritual


In a rite of spring nearly as old as the Nebraska sandhills,
greater prairie chickens and sharp-tailed grouse gather before dawn
on their respective dancing grounds at Valentine National Wildlife
Refuge in the north-central part of the state.


While females watch, the males lower their heads, raise their
tails, spread their wings, inflate colorful air sacs on their necks
and stamp their feet while making hollow cooing or moaning sounds.
The basic purpose of this elaborate display is to attract a
mate.
Indeed, the dancing ground, or lek, is the avian equivalent of a
singles bar, said Dr. Robert Gibson, a behavioral ecologist and
professor of biological sciences at the University of Nebraska.

But
Dr. Gibson, who has studied lekking behavior around the world, is
convinced there is more going on.
While the male grouse assemble every morning from late March to
early May, females come and go, Dr. Gibson said.

"Some days two or
three females will show up, other times none at all," Dr. Gibson
said. "They may visit several leks before selecting a male to mate
with. And it turns out they usually pick the same guy, or a very
small subset of the guys gets chosen.

"
"What you have," he continued, "is a group of males who are
doing something together but only a few of them are
getting anything for it in terms
of reproductive success."
Dr. Gibson says the grouse are looking for more than the
opportunity to pass their genes on to the next generation. "They're
also trying to stay alive in this one by joining a group to evade
predators," he said.


In a paper in The Proceedings of the Royal Society, Biological
Sciences, Dr. Gibson pointed out that conspicuous courtship
displays attracted predators as well as mates, and that grouping to
avoid predation was common in the animal world. He proposed that
male grouse join leks for the same reason.
The birds have a long list of enemies,
including coyotes, foxes, badgers, hawks and golden eagles.

But
during six weeks of watching leks at Valentine, Dr. Gibson and his
research team found evidence to support the hypothesis. "One of the
things we noticed was that male prairie chickens visited
sharp-tailed grouse leks but not vice versa," he said.
Their observations were confirmed when they reviewed the
long-term records of a retired Fish and Wildlife Service biologist,
Leonard McDaniel, who had counted birds on the refuge's 20 to 30
leks every spring.


"If a male prairie chicken's chances of mating are already small
when he joins a lek of his own species," Dr. Gibson said, "it
stands to reason they are not improved at a sharp-tailed grouse
lek. Our finding suggests that they benefit from lekking with
sharp-tails, which in turn implicates predation."
In other words, a male prairie chicken in a sharp-tail lek isn't
necessarily looking for
love in the wrong place he's just
trying to survive.


By Les Line
New York Times - 4/29/2003
Topic: Birding

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