Birds of the Sierra Nevada. Ted Beedy
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public opinion and fashions had changed, and these egrets and most other native birds received protection under the federal Migratory Bird Treaty Act. With strict protection Great Egret populations have largely recovered and the species is now common across most of its former range, including California. Like all colonially nesting birds, Great Egrets are susceptible to human disturbance around their nesting colonies. They may be increasing in winter in the western foothills based on results from some lower elevation West Side Christmas Bird Counts.
Snowy Egret
Egretta thula
ORIGIN OF NAMES “Snowy” for the species’ bright white plumage; egretta from OF. aigrette, egret; thula, a Chilean name for this bird.
NATURAL HISTORY Some birders call Snowy Egrets “golden slippers” because of their bright yellow feet. Similar to Great Egrets, these birds sport brilliant white plumage but they are small and dainty compared with their more common relatives. Snowy Egrets frequent shallow waters along the edges of marshes, slow-moving streams, and canals. They also forage in irrigated fields and pastures with other egrets and herons. They are more active foragers than other members of their family in the Sierra, and often dash through shallow water using their golden slippers and wings to flush unsuspecting prey. Like other egrets and herons, they also stand motionless or stalk slowly while searching for preferred foods, including small fish, crustaceans, and large aquatic insects. On occasion they also consume amphibians, reptiles, worms, and small mammals.
STATUS AND DISTRIBUTION Common residents of the Central Valley, Snowy Egrets rarely venture into the Sierra.
West Side. Rare and mostly confined to the lowlands below about 1,000 feet, Snowy Egrets have been observed at Lake Almanor, Lake Isabella, Lake Wildwood (Nevada County), and in Yosemite Valley in spring, summer, and fall; a single bird was observed in late May at Tuolumne Meadows (about 8,600 feet) in Yosemite National Park, but there are few other records above 4,000 feet; rare to casual in winter at lowest elevations.
East Side. Rare spring and fall visitors to east side marshlands, with individual records from Sierra Valley, Boca Reservoir, Honey Lake, Lake Tahoe, Mono Basin, Grant Lake (Mono County), and Crowley Lake; a pair nested at Mono Lake in the early 1990s, but there are apparently no other nesting records; accidental in winter.
TRENDS AND CONSERVATION STATUS See Great Egret account, above.
Green Heron
Butorides virescens
ORIGIN OF NAMES “Green” for the dark green upperparts of adults; L. butorides probably means “bittern-like”; L. virescens, becoming green.
NATURAL HISTORY Perched on a log or branch at water’s edge with their necks folded, these chunky, crow-sized birds may be difficult to recognize as herons. Green Herons inhabit secluded lakes, ponds, marshes, and slow-moving foothill rivers and creeks that are shaded by riparian trees and often clogged with floating wood. They nest and roost in willows, oaks, and other trees and prefer to forage in their shade. Extremely agile, they climb among wooded tangles while stalking small fish, crustaceans, insects, and rarely small mammals. They also wade or stand in shallow water, much like Great Blue Herons. Sometimes Green Herons hunt from logs or streambanks and may even dive headfirst at their prey. They are known to fish by placing “lures” such as feathers on the water’s surface, thereby attracting their prey close enough to catch.
Unlike most other members of their family, Green Heron pairs are solitary while nesting. In the Sierra their nesting season extends from early March until late June. Both members of mated pairs participate in building nests, which can range from a simple pile of sticks to a more elaborate, woven structure that is reused in successive years. Their nests, up to 18 inches in diameter, are positioned in shrubs and trees up to about 50 feet above the ground. Both parents tend the young until they can fly, about 25 days after hatching.
STATUS AND DISTRIBUTION Green Herons are mostly confined to low elevations of the Sierra.
West Side. Uncommon year-round residents in the lower foothills, usually below about 3,000 feet; rare at higher elevations although Sequoia Lake at 5,300 feet (Fresno County) has two records; possibly present at all seasons except winter, and they are suspected nesters at Lake Isabella, Yosemite Valley, and Lake Almanor.
East Side. Rare spring and summer migrants through the Mono Basin, June Lake, and riparian habitats, with most records from March through June; a few records from Sierra Valley and from Carson Valley.
Black-crowned Night-Heron
Nycticorax nycticorax
ORIGIN OF NAMES “Black-crowned” to distinguish it from the similar Yellow-crowned Night-Heron (Nyctanassa violacea); nycticorax, a night bird, from Gr. nyctos, night, and corax, a crow.
NATURAL HISTORY As their name suggests, Black-crowned Night-Herons forage primarily at night and in the twilight hours. When feeding young, however, they are active all day because food sources may be many miles from their nesting sites. When not nesting, they spend most diurnal hours in large, colonial roosts in dense riparian trees and shrubs or marsh vegetation. Night-Herons forage and roost along densely vegetated lake and pond margins; wet, brushy meadows; and riparian vegetation lining slow-moving streams and canals. They are attracted to fish hatcheries, which provide an abundant source of easily captured prey. Opportunistic foragers, they consume a varied diet of small fishes, snakes, crayfish, and other crustaceans, aquatic insects, and other invertebrates. Night-Herons are also voracious predators of birds’ eggs and nestlings, especially those of colonial-nesting species such as other herons and egrets, White-faced Ibis, and Tricolored Blackbirds. Night-Herons also consume ducks’ eggs and nestlings and may destroy entire clutches of Wood Ducks, Mallards, and Cinnamon Teal.
Highly gregarious, Night-Herons nest in dense rookeries with members of their own species as well as other herons and egrets. Both members of mated pairs participate in building their large nests, which average about 2 feet in diameter and 18 inches in depth. Nests are built from locally available materials including sticks in riparian areas or cattail and bulrush thatch in marsh habitats. In the Sierra their courtship behavior begins in February and nesting continues into July. The young remain in their nests for at least two or three weeks and are tended by both parents. Juveniles attain complete feathering within about a month and can fly within about six weeks. Gregarious even outside the breeding season, large day roosts of many birds are found in marshes and dense riparian areas.
STATUS AND DISTRIBUTION Black-Crowned Night-Herons are mostly confined to low elevations on both sides of the Sierra.
West Side. Rare to locally uncommon in wetlands within annual grassland, foothill chaparral, and oak woodland habitats up to about 1,000 feet in the Yosemite region and somewhat higher in the southern Sierra, as at Lake Isabella (about 2,600 feet), where they reside year-round; casual at Lake Almanor and at Subalpine lakes and marshes in the Yosemite region up to about 9,000 feet in late summer and fall; the probable Sierra altitude record-holder was at Saddlebag Lake near Tioga Pass, just outside Yosemite National Park (10,200 feet) in October 2007.
East Side. Fairly common from March until October in marshlands of Sierra Valley, Honey Lake, and rare visitors to Lake Tahoe; locally common farther south, with colonies at Mono Lake and Laurel Pond (Mono County); they may also nest at Bridgeport Reservoir, Crowley Lake, and in dense emergent marshlands along Hot Creek and the upper Owens River (Mono and Inyo Counties).
IBIS
Family Threskiornithidae
This family includes both the ibises and spoonbills, representing more than 30 species worldwide; five of these exist in North America but only one, the White-faced Ibis, regularly occurs in the Sierra. White-faced Ibis can be distinguished from most other wading birds by their long,