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Mystery Of The Red-Eyed Bird: A Million Eared Grebes
By David Carle, Park Ranger, Mono Lake
Tufa State Reserve
They come in the gloom of the night when no human eyes
are watching. Silently, dark shapes with red eyes descend
from the sky. Thousands upon thousands blanket the black
surface of the lake. They keep on coming. Alfred Hitchcock
never dared dream of a bird invasion of such scale.
Soon three-quarters of a million avian invaders are
here. We call them eared grebes because of a pair of
feathered crests which decorate their heads in breeding
season.
An autumn dawn at Mono Lake allows human visitors their
first look at the nighttime arrivals. At first, all
you may notice are lots of dark dots out on the water.
Look through binoculars and you will see that they are
small, duck-like birds. Then begin to focus across mile
after mile of the surface of this big lake. From the
south shore it is nine miles across. You may see eared
grebes crowding the water through that entire distance.
Eight hundred thousand eared grebes come to Mono Lake
in the fall. That is one heck of a lot of birds of just
one type. We do not really know how many eared grebes
there are in the world. Some guess that one-quarter
of the entire species is here on this lake, all at once.
They come here from nesting grounds in Canada. They
will stay at Mono Lake until the food supply disappears,
as brine shrimp die off in the cold weather of November
or December. Then the grebes head for Central America
to overwinter. At least, we know they end up down there.
No one ever witnesses their nighttime arrivals and departures.
Grebes seem mysterious in other ways. Their looks are
rather strange. They have a dark back, whitish underparts
(which you can see best along the throat), a small,
light cheek-patch, and those unusual red eyes. They
spend a good part of their life under water.
Eared grebes have lobed toes to help them swim. Not
webbed, like ducks, but more as if you had a flap of
tissue sticking out from either side of your fingers.
But the real strange aspect of their body design is
the location of their legs.
Think of a penguin. Its legs are at one end of its
body, so it stands upright on land, sort of like a human.
Underwater, those legs become propellers, located at
the back end of the bird, perfectly placed to shove
them along most efficiently. Eared grebes have "propeller-legs"
at their back ends too, but they are not designed as
well as a penguin's. They swim great underwater, but
they cannot stand up on land.
If you ever see an eared grebe on solid ground, something
is wrong. Every so often someone finds one of these
birds and brings it to us. Who knows why or how they
came to be on land, but once there, they were helpless
to take off again. Did I mention that eared grebes seem
to be weak fliers? At least they really have to work
to take off from the water. They cannot get moving at
all from land, can't even stand upright. The concerned
people think the bird must be sick, since it sits so
quietly. Every time this has happened, we have taken
the grebe to the lake and, happily, it has sped off
across the water, until it was out far enough to dive.
They can stay underwater for a long time. It's a way
to escape, but is used more when they are hungry. Eared
grebes dive for brine shrimp at Mono Lake. They seem
to spend almost as much time underwater as on top of
it. If you have ever gone swimming in the harsh alkaline
waters of this lake, you may remember how it can sting
if you get the water in your eyes. Come to think of
it, maybe that's why the grebes have red eyes. You'd
have red eyes too if you dove under Mono Lake all day
with your eyes open.
Actually, there is a theory that the red color helps
the grebes to see better in the underwater gloom. It
has something to do with wavelengths and penetrability
through the water. Think of amber foglights on a car
— same general idea.
The most impressive thing of all, the thing everyone
keeps coming back to when they talk about these birds,
is their number. Up to 800,000 of them are here in the
fall. Along with the other fall migrants and birds that
have been here all summer, the grebes help make autumn
the "birdiest" time of year at Mono Lake.
Sometimes they mass so closely together that it seems
like you could walk across the lake on the back of grebes.
Think about that number — 800,000 — for a
moment. If each grebe takes up about 12 inches, and
they sat end to end, they would extend 150 miles! Good
thing Mono Lake has about 60 square miles of surface
where they can spread out.
Their combined weight totals somewhere in the vicinity
of 100,000 pounds. Who cares, you ask? The amazing thing
about their weight is that they will double it here
in just 30 days, gorging themselves on brine shrimp.
That's a clue as to just how many shrimp the lake produces
(millions of pounds of the tiny little creatures!).
The irony of all of this is that Mono Lake is still
referred to by some misinformed writers as a "dead
sea." In truth, it is a super-productive ecosystem,
supporting far more life than the fresh-water lakes
of this area — relative deserts by comparison.
I am impressed by eared grebes. They help to make Mono
Lake unique. They remind us of their importance of this
place to other sites thousands of miles away in Canada
and Central America.
But I have to admit that I don't relate well to them.
They fly by night. They spend a lot of time underwater
where I can't see what they are up to. They are almost
always silent. They hang around enormous crowds that
only a New Yorker could love.
Some mysterious night, late in the fall, they will
startle us again by disappearing into the gloom. Soon
after, somewhere in Central America, dark, silent, red-eyed
figures will descend from the sky.
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