Clear Lake is known for its abundant wildlife. Thousands of birds visit the lake each year and one of the most popular is the western grebe.
A number of local bird watchers are concerned the popular bird could be in trouble at the lake. In 1990, the estimated population of western grebes at Clear Lake was more than 70,000. This year there are less than 5,000.
Some of the grebes are building nests, but many are abandoning them after the eggs are laid. A good example is the small lagoon near the Lakeside County Park.
Two weeks ago I counted 14 nests with grebes sitting on the eggs. On Sunday, I observed only two nests with grebes. The other 12 had been abandoned and the eggs were exposed. It”s been the same in other prime nesting areas on the lake.
Historically the western grebe selected Clear Lake as a nesting area because of the perfect nesting habitat and abundance of small fish, but the past three years saw very little successful nesting of the grebes. Only 14 grebe chicks were seen last year — compare that to 10 years ago, when they numbered in the thousands.
Like all wildlife, the driving force for the grebes and other bird life on the lake is food and habitat. Nature has hard, fast rules for all wildlife. If there isn”t a sufficient food supply the young won”t be born or hatched. For example, when the food supply is scarce doe deer will abort their young. The same rule applies to all wildlife.
Some experts theorize that the reason the grebes were at Clear Lake in such massive numbers 10-15 years ago was the abundance of the threadfin shad. The past five years saw very few shad and even the silverside minnows (another prey fish for the grebes) have been in short supply.
Another major factor could be the vast weed beds that cover the lake. The weeds have been thicker in the lake in the past three years than in decades. The thick aquatic weeds create excellent cover for the small fish that the grebes feed on.
Grebes feed on all species of small fish. This year the Department of Fish and Game electro-shocking study revealed a large population of small bass. Normally the grebes would utilize this food source, but this year the little bass can find cover from the grebes in the dense weed patches.
The grebes mating dance is one of the most spectacular sights on the lake.
The male approaches the female and does a series of dips with his head. She responds with similar 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. Both will 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 will lay from one to four eggs. It takes 23 days for the eggs to hatch.
The young leave the nest soon after being hatched and feed on small minnows that their parents catch for them. They also ride on their parents” backs. The adult assists the chicks to get on the adult”s back by extending its foot as a small platform.
According to wildlife biologists, grebes have 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 delicate lining of their stomachs.
Actually there is little that can be done to increase the food supply for the grebes and increase the nesting success. It”s all part of the swings of nature and applies to all living creatures. The good news is that the state”s overall western grebe population appears to be healthy and thriving.
