Local lakes provide important grebe habitat
By this point in mid-summer, western and Clark’s grebes have been on our Plumas County lakes for a few months. These large water birds have distinctive red eyes and are quite common in our region. Their raspy calls travel across the water with ease and can be heard from a great distance. They nest on lakes and swamps that support healthy fish populations from here all the way out to Minnesota and from Mexico up into Canada. The grebes in our region are important, however, because about 30 percent of the nesting colonies occur in Northern California.
Grebes mainly winter along the Pacific Coast or on warm inland lakes such as the Salton Sea in Southern California. They subsist on small fish; adult birds may consume a pound of fish per day. Their migration is a phenomenon that is poorly understood by biologists; many people believe that they fly under the cover of darkness and rely on numerous stopover lakes along the way. The fact that these water birds can even make the trip is an incredible accomplishment. They have small wings and do not fly well. Once the grebes reach their destination they shed all of their flight feathers and become flightless for a period of time. This causes their flight muscles to atrophy and they remain flightless until the availability of food becomes scarce in the fall.
Grebes have some of the most elaborate courting rituals of all birds. Their displays seem to correspond to the progression of the breeding season. Early on they can be seen pairing off and performing a dance where they preen themselves and bob their heads at one another. Later as they are about to build their nests they can be seen diving and returning to the surface with vegetation that they present to their mate. The most remarkable part of these courting rituals is called the rushing display. Maybe you have seen it. The grebes rear up in a near vertical position; they tuck their stubby wings and throw their heads back while running across the surface of the water. It is quite a sight. Some grebes can cover up to 100 feet during this display.
The grebe has adapted to pursuing prey underwater. They have a slender body, dense bones and lobed toes that allow them to travel underwater with surprising agility. Their legs are set far back on their body, which increases their ability to propel themselves underwater. These physical traits may help the grebes in the water but it makes them quite ungainly on land where they are rarely seen.
Grebe pairs team up to build their floating nests, which they prefer to build in two – six feet of water. This allows them easy access to their hunting grounds and it also reduces the threat from terrestrial predators such as raccoons, skunks, dogs and cats. They gather decaying organic materials and weave them into the vertical stalks of vegetation that is rooted to the lake bottom. This anchorage is necessary in order to prevent the nest from floating away during times of high winds and waves. Once the nests have been completed they use them to copulate, which can begin long before the eggs are laid. Once the eggs are in the nest the birds take turns incubating them, which takes around 30 days.
This year grebes have already begun to lay and incubate eggs. We have been monitoring their progress on Lake Almanor and Eagle Lake. Although these are our two most significant breeding lakes, they also nest on Mountain Meadows Reservoir, Lake Davis, Round Valley Reservoir and Antelope Lake. At Lake Almanor the grebes are in a race against falling lake levels and we are rooting for the grebes. With the high water that we are experiencing this summer they have built their nests in areas that will be high and dry before too long. PG&E has begun to release water from the lake and we are hoping that the eggs will be hatched before the floating nests are no longer in the water. The parents abandon their nests if they become stranded on land and if this happens the eggs will be eaten by predators.
Unlike many other birds, the grebes leave their nest for good once their young have hatched. The fuzzy hatchlings are shuttled onto one of the parent’s backs and they begin their aquatic lives. During this time one of the parents dives for food and brings it back to share with the family. The grebes carry their young for the first six – seven weeks until they are ready to learn how to swim and dive for their own food. If you are out on the lakes and you see grebes carrying young on their backs please to try to steer clear of them. The newly hatched babies cannot swim or dive for their first few weeks. Also be sure to dispose of tangled fishing line or other garbage properly because numerous birds die each year due to entanglement.
Once the young birds have learned to forage and their bodies have developed they begin to learn how to fly. The whole family builds the strength of their flight muscles together through a series of exercises; once they are ready they disappear from these lakes before the cold weather descends upon the mountains. Then our lakes are quiet once again until next spring when the grebes return and announce their arrival with their rusty call kreek kreek.