Birds of the Sierra Nevada. Ted Beedy
Читать онлайн книгу.about seven weeks.
In the nonbreeding season, these bright-colored ducks occur in small flocks, often in association with other puddle ducks or American Coots. Cinnamon Teal forage primarily at the edges of ponds and sloughs for bulrushes, pondweed, and sedges. They also consume a limited amount of animal food when breeding, mostly bugs, beetles, and snails.
STATUS AND DISTRIBUTION Unlike most puddle ducks, Cinnamon Teal winter primarily in Mexico and fly north to breeding grounds in fresh and brackish marshes in the western United States and southern Canada.
West Side. Uncommon nesters at ponds, reservoirs, and marshes of the lower foothills, spring migrants arrive by early March and remain through mid-September; nesting confirmed at Lake Isabella and Lake Almanor; rare in winter in Kern River Valley and southern foothills; rare visitors above 3,000 feet in the central Sierra during spring and fall migration.
East Side. Common nesters in marshlands from Honey Lake south into the Owens Valley; rare or casual in winter.
Northern Shoveler
Anas clypeata
ORIGIN OF NAMES “Shoveler” refers to the species’ shovel-shaped bill; L. clypeum, shield, another reference to bill shape.
NATURAL HISTORY Called “Spoonies” by hunters, Northern Shovelers have large, flattened bills that resemble spoons. These specialized bills have comb-like teeth (called “lamellae”) on the mandibles, through which food is strained from shallow water or mud. They primarily feed in shallow water, where aquatic prey float near the surface; unlike most other puddle ducks, they never forage on land. Shovelers are highly carnivorous and primarily consume crustaceans, snails, tadpoles, caddisflies, damselflies, and the nymphs and larvae of other aquatic insects. They also use their shovel-like bills to scoop up organic material from muddy pond bottoms. Their highly sensitive tongues make it easy to accept or reject potential food items. Shovelers tend to be monogamous and mated pairs can stay together for several years or more.
Shovelers occur in a variety of wetland habitats ranging from small ponds to large reservoirs and are especially fond of sewage treatment ponds. The primary requirement appears to be the presence of large quantities of invertebrate animal food. They congregate on large bodies of open water for roosting to avoid predators. They prefer ice-free lakes that provide access to pond bottoms, and for this reason they are among the first waterfowl to depart their breeding grounds in Alaska and Canada in late summer.
STATUS AND DISTRIBUTION Northern Shovelers begin to arrive in California by late August, and most depart for northern breeding grounds by early May.
West Side. Uncommon visitors to the lower foothills, migrants observed to above 3,000 feet in the central Sierra; possible nesting at Lake Isabella and Lake Almanor.
East Side. Uncommon but becoming more regular in winter; common during spring and fall migrations at large wetlands, including Sierra Valley, Bridgeport Reservoir, Mono Lake, and Crowley Lake; possible nesters in Sierra Valley.
TRENDS AND CONSERVATION STATUS In the fall of 1948, almost a million Northern Shovelers were recorded at Mono Lake, demonstrating this was once a major staging area for the species in the eastern Sierra. However, after more than 50 years of water diversions from its major tributary streams, Mono Lake’s surface area dropped and the lake became too alkaline and salty for most puddle ducks, including shovelers. With the return of freshwater flows to the lake since the mid- 1990s, waterfowl are starting to return to the lake, and hundreds of shovelers can now be seen, especially near the springs and creek deltas along the eastern lakeshore. North American breeding populations appear to be stable to increasing. Christmas Bird Counts on both sides are recording higher numbers since the early 1990s.
Northern Pintail
Anas acuta
ORIGIN OF NAMES “Pintail” refers to the species’ long, pointed tail feathers; L. acuta, pointed.
NATURAL HISTORY Among the most stylish waterfowl, male Northern Pintails are large, elegant ducks. Like other puddle ducks, they are primarily surface feeders that dabble in shallow water. Pintails mostly consume vegetable matter such as pondweeds, sedges, and grasses. They are drawn to agricultural crops, especially flooded rice fields where waste grain is abundant. Organic rice fields, especially those with wild rice are preferred. In summer they consume small fish, frogs, mollusks, and the larvae and nymphs of aquatic insects.
Northern Pintails have a wider global distribution than any duck, and breed or winter on all continents except for Australia and Antarctica. A few Northern Pintails nest in the Sierra, but most of their population migrates north or east to breed. They are among the first migrant waterfowl to arrive in California, usually by mid-September; many continue south to winter in Mexico, Central America, or northwestern South America. Pintails nest in open, wetland habitats with low emergent vegetation such as cattails and tules. Nesting sites are usually on islands or small berms surrounded by water. The nest is a small scrape or depression lined with plant material, feathers, and down.
STATUS AND DISTRIBUTION Abundant winter visitors to the Central Valley and coastal California, Northern Pintails occur regularly on both sides of the Sierra but rarely in large numbers.
West Side. Uncommon fall, winter, and spring visitors to ponds and reservoirs of the foothills up to about 3,000 feet in the central Sierra; possible nesters have been observed at Lake Almanor and Lake Isabella.
East Side. Fairly common spring and fall migrants; a few pairs nest annually in marshes of Honey Lake, Sierra Valley, and Crowley Lake; winter status is variable, with few to none some winters and many in others.
TRENDS AND CONSERVATION STATUS In contrast to most species of waterfowl, Northern Pintails have shown generally negative population trends in recent decades. Data from California Christmas Bird Counts show that winter numbers are down significantly. Data from Sierra Christmas Bird Counts are insufficient to determine trends, but most circles are reporting smaller numbers than those seen in the 1970s and 1980s.
Green-winged Teal
Anas crecca
ORIGIN OF NAMES “Green-winged” refers to the bright wing patches of males and females; crecca, possibly a Latinized word to describe the species cricketlike calls.
NATURAL HISTORY Green-winged Teal are the smallest North American dabbling ducks and weigh less than a third of Mallards. These tiny ducks tend to stay at pond margins and in dense vegetation, sometimes making them hard to see. Like other teal, they have a rapid turning flight, low over water. Nesting sites are in sedge meadows or grasslands near ponds or other sources of permanent water. Females excavate small bowls lined with soft plant material, feathers, and down hidden in dense vegetation surrounded by water. Primarily vegetarians, they forage in shallow water by wading or swimming. Preferred foods are seeds of aquatic plants such as bulrushes, sedges, wild rice, smartweed, and wild millet. In summer they consume mostly animal foods such as beetles, bugs, and dragonfly and damselfly nymphs.
STATUS AND DISTRIBUTION Most of the Green-wing Teal wintering population migrates north and east to breed, but a few remain to nest and stay in California through the summer.
West Side. Uncommon visitors to marshes, ponds, and reservoirs of the foothills in fall, winter, and spring; possible breeding at Lake Almanor, and confirmed breeding at Lake Isabella.
East Side. Common spring and fall migrants to lakes and reservoirs, where they congregate in large flocks in fall and winter; uncommon breeders throughout the region.
Canvasback
Aythya valisineria
ORIGIN OF NAMES “Canvasback” for the