With spring just around the corner, the bird watchers are wondering if the western grebes will return in large numbers to Clear Lake again this year.
There were very few grebes and no nesting activity last spring. In fact, there were no nests and not a single baby grebe was seen riding on its mother”s back. Compare that to previous years when the grebes were here by the thousands and had massive hatches.
In January of last year there were an estimated 30,000 western grebes on the lake, but they were nearly all gone by March. The grebes did return in July, but not to nest. They were here because of the spawning threadfin shad. The shad population exploded and then crashed. When the shad died off, the grebes once again left the lake to find more fertile grounds.
According to wildlife biologists, the grebes probably dispersed over a number of lakes in the West. Grebes tend to migrate at night and are rarely seen flying.
There was a similar situation in 1990 when the threadfin shad population reached its peak at Clear Lake. An estimated 70,000 grebes converged on Clear Lake at that time and it was considered the largest population of grebes anywhere in the world. That was also the year the shad population crashed. Like this year, the grebes left for other lakes.
Like all wildlife, the driving force for the grebes and other bird life on the lake is food and habitat. The reason the grebes visited Clear Lake in such massive numbers was because of the abundance of the threadfin shad. The lake has been literally awash with shad the last three years. A fragile fish, shad usually see their population go up and down like a roller coaster.
A spell of cold weather will kill thousands of shad. Insufficient food also causes massive die-offs. Shad feed on plankton and one reason there have been so many shad in the lake in recent years is because the lake is rich in plankton. But as the amount of plankton decreased, the shad”s major food source dried up.
Grebes are popular among bird watchers because of their courtship dance in the spring. The male approaches the female and does a series of dips with his head. She responds with like dips and then they run across the surface of the water with their necks arched in perfect unison. Their final act is to dive exactly at the same time. This maneuver is called “rushing” and the birds actually swim so fast they hydroplane.
Western grebes also perform what is called the “weed ceremony,” which occurs after the grebes have paired up and just before they start building nests. The male and female dive and bring up weeds in their bills. They face each other and do a spiral dance.
Both the male and female build the nest and raise the young. They use tule stalks to make a floating mat and then build the nest on the mat. The female lays from one to four eggs and it takes 23 days for the eggs to hatch. The young leave the nest soon after being hatched and they often ride on their parents” backs. The male or female helps the chicks onto their backs by extending a foot and using it as a small platform.
According to wildlife biologists, grebes possess another trait that is unusual. They tend to consume a lot of feathers, not as food but to form a feathery ball in their stomach. It is thought that the purpose of the feathery ball is to keep fish bones from damaging the lining of their stomachs.
Western grebes do fly although most people have never seen one more than a few feet off the ground. In fact, many of the western grebes at Clear Lake migrated here from as far north as Canada. Biologists have attached small radio transmitters to grebes and have learned they normally make short flights and move from lake to lake. If they find sufficient food and good nesting conditions, they will stay at a lake. However, if there is a shortage of food they will move on to other lakes.
Clear Lake has ideal nesting habitat for grebes but food can be scarce at times. So far this year there hasn”t been many threadfin shad although that could change if the remaining shad have a good spawn. Silverside minnows are another important food source for the grebes.
It would be a shame if Clear Lake”s most popular water bird doesn”t return in large numbers. Without a doubt the western grebe has been one of the main attractions at Clear Lake.
