Birds of the Sierra Nevada. Ted Beedy
All grebes have soft, thick plumage. Feathers are consumed incidentally while preening and form into balls in grebes’ stomachs, which may function to protect the linings of their stomachs and intestines from being punctured by fish bones. Feather balls also serve as the nuclei of pellets that are regurgitated to eliminate bones and other indigestible materials. Of about 20 grebe species in the world, 7 occur in North America, and 5 of those occur regularly in the Sierra. The family name was derived from L. podicis, rump, and pedis, a foot, and roughly means “rump-footed.”
Pied-billed Grebe
Podilymbus podiceps
ORIGIN OF NAMES Podilymbus, a diving bird, from L. podiceps, a grebe, and Gr. kolumbos, a diving bird; podiceps ( see family account above); “grebe” is an OF. word of unknown origins.
NATURAL HISTORY Generally solitary, with subdued brownish plumage, Pied-billed Grebes may go unnoticed when swimming along the dense vegetation at a pond’s margin. They dive for aquatic insects, crustaceans, or small fish in shallow waters and consume smaller quantities of tadpoles, mollusks, and aquatic plants. They also frequent deeper, open waters where they rest with other grebes or with larger coots and ducks. Most water birds take flight when predators approach, but Pied-billed Grebes sink quietly beneath the surface and reappear amid floating plants with only their heads out of water. They are typically found in quiet ponds, backwater sloughs, lakes, and reservoirs. Although they occur on water bodies from one-half to over 100 acres in size, Pied-billed Grebes are most often seen on ponds ranging from 1 to 5 acres. They prefer open water bordered by dense cattails, bulrushes, and other emergent vegetation.
Most grebes are colonial when nesting, but Pied-billed pairs are solitary. Both parents gather dead and rotting plant materials to build a thick mat nest that occasionally floats free but is usually anchored to plants growing from the bottom ooze. Their breeding season extends from about mid-March to mid-September, though peak breeding activity occurs from late June to early July. Each pair defends a small territory around the nest, where the young are fed and reared. Newly hatched chicks often ride on the adults’ backs or hide beneath their wings during dives.
STATUS AND DISTRIBUTION Unlike other grebes, most Pied-billed Grebes do not migrate to salt water for the winter and prefer to reside year-round in freshwater habitats.
West Side. Fairly common residents and nesters throughout the foothills, they also nest rarely up to the Upper Conifer zone but are scarce anywhere above about 5,000 feet; a few breeding pairs have been found above 7,000 feet in the Subalpine zone of Plumas County, and postbreeding birds occur up to about 8,000 feet in Yosemite and Sequoia National Parks during late summer and fall; flocks of up to 300 individuals have been seen at Salt Spring Valley Reservoir (Calaveras County) in winter.
East Side. Fairly common permanent residents and nesters below about 7,000 feet, rare fall migrants have been seen at Alpine lakes up to about 9,000 feet in Yosemite National Park; numbers increase noticeably in October and November when they congregate at large reservoirs such as Crowley Lake and Bridgeport Reservoir; rare in winter, most depart before their preferred freshwater habitats freeze over.
Horned Grebe
Podiceps auritus
ORIGIN OF NAMES “Horned” for the tufts of feathers on the heads of breeding adults; L. auritus, eared; for unknown reasons taxonomists applied the scientific name to this species instead of the Eared Grebe, which was named instead for its neck color.
NATURAL HISTORY Foraging Horned Grebes dive after small fish, crustaceans, and aquatic insects. Similar to other grebes, they also dive to escape danger and can swim for long distances before coming to the surface. Although they sometimes share open waters of large lakes and reservoirs with Eared Grebes, Horned Grebes tend to be much less gregarious and are less likely to occur in large flocks on their wintering grounds or during migration.
STATUS AND DISTRIBUTION Horned Grebes do not breed in California, and most of the state’s visitors are found in coastal waters from October through April. A few, however, are drawn to lakes and reservoirs of the Sierra. This species is probably overreported, especially in fall when transitional plumages of Eared Grebes can blur the distinction between these species.
West Side. Uncommon fall, winter, and spring visitors to Lake Almanor, Millerton Lake, Avocado Lake (Fresno County), Lake Isabella, and other large lakes and reservoirs.
East Side. Uncommon to rare spring and fall visitors to such lakes as Boca Reservoir, Lake Tahoe, Topaz Lake, Grant Lake (Mono County), and Crowley Lake.
Eared Grebe
Podiceps nigricollis
ORIGIN OF NAMES “Eared” for the feather tufts; nigricollis, black-necked, from L. niger, black; L. collum, neck.
NATURAL HISTORY These small, thin-billed grebes congregate at Mono Lake in enormous numbers during fall migration to feed on the superabundant brine shrimp that thrive in the lake’s highly alkaline and saline waters. At the peak of their fall migration, they may consume more than 60 tons of brine shrimp daily (Winkler et al. 1977)! They also consume alkali fly larvae in shallow, nearshore waters, and the flies represent about 10 percent of their diet. Huge quantities of food are needed because the grebes are molting and rebuilding their fat reserves before continuing their migration. At freshwater habitats elsewhere in the Sierra, Eared Grebes consume mostly insects (adults and larvae), crustaceans, mollusks, and occasionally small fish and tadpoles. They usually forage by diving and capturing prey underwater but sometimes take insects from the water’s surface.
Mono Lake is the Eared Grebe’s largest fall staging area in North America. From breeding grounds across the western United States and Canada, birds begin to arrive at the lake in June, and the summer flock may contain more than 25,000 birds, mostly juveniles and nonbreeders. Postbreeding Eared Grebes arrive at Mono Lake at rates of up to 10,000 birds per day in late summer and fall, and numbers may peak at more than a million birds in September and October. Large numbers of Eared Grebes usually remain at Mono Lake until late November, when the brine shrimp population collapses and the grebes continue their migration on to the Salton Sea, San Francisco Bay, or the Gulf of California.
Nesting activities extend from late April until late September, with a peak from June through mid-August. Both sexes participate in building the nest, a hollowed-out mound of rotting vegetation hidden by similar material and located on the ground or floating and anchored to submerged, upright plants. Juvenile Eared Grebes can fly about 45 days after hatching and promptly begin their fall migration.
STATUS AND DISTRIBUTION Eared Grebes nest in freshwater habitats, but most seek highly alkaline and saline waters during migration through the Sierra and on their wintering grounds.
West Side. Fairly common year-round residents only at Lake Almanor and at Lake Isabella, where hundreds or thousands overwinter and a few remain through the summer; elsewhere, uncommon and irregular visitors to large lakes and reservoirs in fall, winter, and early spring; rare migrants have been seen at large Subalpine and Alpine lakes of Yosemite and Kings Canyon National Parks in late summer and fall.
East Side. Common nesters in marshes of the Great Basin, just east of the Sierra, and small numbers nest locally in shallow wetlands near large waters in the eastern Sierra, including Honey Lake, Crowley Lake, and Bridgeport Reservoir; uncommon to absent in winter except for Mono Lake, where the local Christmas Bird Count tallies hundreds or even thousands some years, and the Reno area, where double-digit numbers are not unusual.
TRENDS AND CONSERVATION STATUS A historic 1994 decision by the State Water Resources Control Board should ensure that Mono Lake’s waters will not become too alkaline and salty to support abundant brine shrimp and alkali flies for Eared Grebes and other water birds. While their habitat appears secure in the eastern Sierra, mortality in other parts of the