Birds of the Sierra Nevada. Ted Beedy
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viable, diverse populations of birds in the Sierra and elsewhere.
Family and Species Accounts
WATERFOWL
Family Anatidae
Of almost 30 waterfowl species observed regularly in the Sierra, most pass over during spring and fall migration and only about half of those breed in the region. Most members of this family frequent low-elevation marshes, ponds, and reservoirs, but a few visit Alpine lakes and turbulent streams of the high country.
Waterfowl are distinguished from other birds by their bills, which are blunt, somewhat flattened (except for mergansers), with a hard tip, or “nail.” All species are excellent swimmers and well adapted to aquatic living, with webbed feet, long necks for underwater feeding, and thick coats of down. The region’s ducks can be roughly divided into two groups based on foraging techniques and corresponding anatomy: dabbling ducks, which are generally agile on land and feed by tippingup in shallow water; and diving ducks, which generally feed by diving and swimming under water. Diver’s legs are positioned far back on their bodies to help them dive and swim but render them nearly helpless on land, requiring them to run across the water’s surface before taking flight.
Swans and geese usually mate for life, and males and females wear identical plumage. Ducks are sexually dimorphic, with males displaying bright, well-marked breeding plumages and using elaborate courtship displays to attract the more subtly patterned females. Most duck species undergo a postbreeding molt into “eclipse” plumage that leaves the males looking very similar to females for about two months. The timing of this molt usually corresponds to a flightless period when flight feathers are replaced. This is followed by a molt of body feathers that produces the typical bright male plumage in time for the winter courtship season.
Ducks typically mate for a single season, with males taking no part in incubating eggs or caring for young and abandoning their mates soon after the last egg is laid. Waterfowl eggs are white, buff, or greenish in color and lack spots or other patterns. Geese and swans usually lay about five eggs, while most ducks lay five to more than ten. Females of most waterfowl incubate eggs for 20 to 30 days, and the precocial young can walk, swim, and feed immediately after hatching; they can fly after five to seven weeks—sooner for ducks than for swans and geese. Ducks are also sexually dimorphic in voice, due to an asymmetrical enlargement of the male’s windpipe (the tracheal bulla). This causes them to emit low grunts and whistles rather than the louder, and perhaps more familiar, vocalizations of females. This diverse, cosmopolitan family includes about 145 living species and 4 recently extinct species. The family name was derived from L. anas, a duck.
Greater White-fronted Goose
Anser albifrons
ORIGIN OF NAMES “Greater” to distinguish it from the “Lesser” White-fronted Goose (A. erythropus), a native of Eurasia; “white-fronted” for the margin of white feathers surrounding their bills; L. anser, goose; L. albifrons, white forehead.
NATURAL HISTORY Some hunters call these birds “speckle-bellies” or “specs,” perhaps a more apt description than “White-fronted Goose.” The bold, horizontal barring on the bellies of adult birds is visible in flight, unlike its namesake white patch (“front”) at the base of the bill that can be seen only at close range. White-fronted Geese graze on grasses, fallen grain from harvested fields, and aquatic plants while on the wintering grounds. Winter flocks numbering in the tens of thousands roam rice fields and wetlands in search of abundant sources of food, where they mingle with white Snow and Ross’s Geese. White-fronts travel in V-shaped wedges high above the landscape, frequently uttering loud, laughing calls—somewhat reminiscent of high-pitched barking dogs; these double or multisyllabic calls are unlike those of other geese.
STATUS AND DISTRIBUTION Greater White-fronted Geese breed in the high Arctic regions of Alaska and northwestern Canada, and they winter abundantly in California and other southern states. They are among the first of the northern breeders to arrive in California, and wintering flocks can be seen by mid-September. They are also the last geese to depart in spring, and migrating flocks fly over river canyons in the northern Sierra until at least mid-April.
West Side. Uncommon spring and fall migrants, a few individuals land on large, reservoirs; individuals rarely seen in flocks of Canada Geese on Sierra golf courses and wet meadows.
East Side. From late February through early April, thousands congregate in Sierra Valley and Honey Lake prior to departing for northern breeding grounds; uncommon spring and fall migrants and overwintering birds recorded at most large lakes and reservoirs.
TRENDS AND CONSERVATION STATUS White-fronted Geese have made a dramatic comeback across North America, including wintering populations in California. The lowest populations were recorded in the 1970s, but reduced harvest levels implemented in the 1980s allowed their populations to increase dramatically by the mid-1990s. Christmas Bird Count data showed a tenfold statewide increase from lows of fewer than 10,000 in the early 1970s to more than 110,000 in 2010. Creation of wintering habitat has increased winter survival, and earlier snowmelt at northern breeding areas has resulted in increased breeding habitat.
Snow Goose
Chen caerulescens
ORIGIN OF NAMES “Snow” for the white plumage of adults; Gr. chen, goose; L. caerulescens, bluish, for the blue color morph of this species.
NATURAL HISTORY Thought to mate for life, Snow Geese remain in family groups and have strong family ties maintained for many years. The young do not breed until at least three years old, so family units can be quite large. Flock formations are not as organized as for other geese, and Snow Geese fly in loose wedges and long diagonal lines that may extend for miles. Among the most social of all waterfowl, Snow Geese often concentrate in huge flocks sometimes numbering more than 100,000 birds milling about in productive feeding areas. They fly up to 30 miles between feeding and roosting sites, and large flocks descending into a field can resemble falling snow. Wintering and migratory birds roost on water but forage mostly on land. Entirely vegetarian, they are drawn to recently harvested rice fields and grain stubble but also forage on bulrushes and other marsh plants in winter and on freshly sprouted grasses in spring. Once classified as a separate species, the rare (in California) “Blue Goose” is a dark color morph of the far more abundant Snow Goose and represents a tiny fraction of the species’ wintering population.
STATUS AND DISTRIBUTION Although they are abundant winter residents of the Central Valley, Snow Geese are only infrequent migrants over the Sierra in fall (early October to mid-November) and spring (mid-March to early April) that land occasionally on large lakes and reservoirs.
West Side. Uncommon spring, fall, and winter visitors to Lake Almanor but rare elsewhere; flocks sometimes numbering more than 500 birds cross the Sierra every year, primarily north of the Yosemite region.
East Side. Fairly common migrants through Sierra Valley and Honey Lake in spring and fall; rare or casual farther south.
TRENDS AND CONSERVATION STATUS Snow Goose populations in North America have quadrupled since the 1970s, possibly in response to increases in wintering carrying capacity created at refuges and in flooded rice fields. Their population explosion has impacted breeding habitat conditions throughout their range. Breeding birds are having major impacts on Arctic tundra environments by grubbing for roots and tubers disturbing the fragile soil and denuding large areas. Recently liberalized hunting seasons have been implemented to reduce populations to historic levels.
Ross’s Goose
Chen rossii
ORIGIN OF NAMES “Ross’s” for Bernard Rogan Ross (1827–1874), a trader for the Hudson’s Bay Company in the mid-1800s who collected many bird specimens, including this goose.