Clear Lake is known for its wide diversity of fish and wildlife. One of the most photographed birds on the lake is the Western grebe. The lake was host to more than 50,000 Western grebes a year ago, making it one of the largest concentrations of the birds in the West. The tule-lined shoreline from Lakeport to the state park are the primary nesting area for the grebes.
As late as January of this year, there was an estimated population of more than 30,000 Western grebes on Clear Lake. In the Narrows between Glenhaven and Clearlake Oaks, there were so many grebes, seagulls, pelicans and terns that it was impossible to see the water at times.
In a few short weeks these birds have all but disappeared. In fact, there are very few grebes at the traditional nesting areas. Where have they gone and why? That”s the question many people are asking.
Like all wildlife, the driving force for the grebes and other birds at Clear Lake is food and habitat. The reason the grebes were at Clear Lake in such massive numbers was because of the abundance of threadfin shad. The lake literally has been awash with shad the last three years.
Threadfin shad are a fragile fish and their population tends to 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 is because the lake is rich in plankton. As the plankton has decreased, there has been less food for the shad.
Another factor could be the thousands of birds that have been feeding on the shad the past two years. The lake is also loaded with bass, crappie and catfish, all of which feed on the shad.
As the shad population dwindled, the grebes left Clear Lake for other lakes. According to wildlife biologists, the grebes probably dispersed over a wide area that includes a number of lakes in the West. Grebes tend to migrate at night and are rarely seen flying.
A similar situation occurred in 1990 when the threadfin shad population was at its peak in Clear Lake. There was an estimated 70,000 grebes here at that time and it was considered the largest population of grebes anywhere in the world. That also was the year the shad population crashed. Like this year, the grebes left for other lakes.
Grebes are popular among birders 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.
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. This allows the chicks to rest and to escape danger.
The threadfin shad and grebes will return to the lake. For example, in 1992 it was thought that all the shad had died, but by 1995 the shad were back. The grebes also returned.
The crash of the shad population will have minimal impact on the bass population. The lake still has a good population of crayfish and minnows of other species (all which supply the bass with a food source). It just means the bass and other game fish will have to work a little harder for their next meal.
