of the Hooded Merganser’s western population breeds along the Pacific Coast from southeastern Alaska south to Oregon. Historically they were not considered a breeding species in California, but they have expanded their range southward into the state in recent decades. Hooded Mergansers nest in tree cavities and make use of old woodpecker holes as well as artificial nesting boxes that have been installed widely in California for Wood Ducks—most of the state’s recent nesting attempts have been in boxes.
STATUS AND DISTRIBUTION Grinnell and Miller (1944) described the Hooded Merganser’s status in California as: “Winter visitant, relatively rare . . . never within history appreciably more numerous than now.” Since the mid-1960s, however, more than 100 Hooded Merganser nesting attempts have been documented in at least 20 California counties (Pandolfino et al. 2006). The number of wintering birds in the state has also increased in recent decades.
West Side. Fairly common and widespread winter visitors and spring and fall migrants to wooded lakes and ponds of the foothills regularly up to about 4,000 feet in the central Sierra; most recent nesting records from Plumas, Sierra, and El Dorado Counties, rare or casual south of the Yosemite region.
East Side. Common winter visitors to the Tahoe region, where they are regularly observed Lake Tahoe, Donner Lake, Glenshire Pond (Nevada County), the Truckee River west of Reno; otherwise uncommon migrants and rare in winter; no breeding records.
TRENDS AND CONSERVATION STATUS As noted above, the breeding range of this species has expanded into northern California in recent years. Data from California Christmas Bird Counts show a dramatic increase in the winter population as well. Sierra counts show an even greater positive trend, with numbers up nearly six-fold from the early 1980s.
Common Merganser
Mergus merganser
ORIGIN OF NAMES “Merganser” from L. mergus, a diver.
NATURAL HISTORY These expert underwater hunters require fairly clear water to see their prey. Their long, thin bills have horny tooth–like projections that prevent slippery fish from escaping their grasp. This feature has earned them the epithet “sawbill.” Due to their large size, they are also called “Goosanders” in Europe.
Although they are mostly fish-eaters, Common Mergansers also forage for a diversity of aquatic insects, crayfish, mollusks, amphibians, small mammals, birds, and aquatic plants. These mergansers are often accused of depleting fisheries, but their total impact on fisheries is negligible since they rarely occur in large numbers in any given area. Like other diving ducks, Common Mergansers are clumsy on land and must run across water to take flight. Once flying, their long, straight bodies knife through the air just above the water’s surface, flashing white wing patches. They can be told from all other Sierra ducks by their sleeker profiles and long, narrow bills.
Common Mergansers nest in tree cavities or rock crevices near large streams or lakes; rarely they use artificial nest boxes. Breeding begins in April, and the young can navigate the swiftest streams within a day of hatching. One merganser duckling attempting to cross the Merced River at flood stage was sucked under the waves only to appear about 100 yards downstream, unhurt, and bobbing like a tiny cork. Females tend their young alone until they are independent after about five weeks.
STATUS AND DISTRIBUTION Aside from the ubiquitous Mallards, Common Mergansers are the most abundant and widespread breeding ducks in the Sierra, where they reside year-round.
West Side. Fairly common along most large creeks and rivers offering clear water and plentiful supplies of fish; most Sierra breeding records are from forested lakes and streams below about 8,000 feet; postbreeding birds can range to above 9,000 feet in the central Sierra in late summer and fall; flocks of 5 to 30 individuals remain on ice-free lakes and rivers at the highest elevations year-round, but most move to lower-elevation lakes, rivers, and reservoirs for winter; thousands winter on Lake Isabella.
East Side. Common at Lake Tahoe; fairly common to common in winter and during spring and fall migration at most large rivers, lakes, and reservoirs.
Red-breasted Merganser
Mergus serrator
ORIGIN OF NAMES “Red-breasted” for the coloration of breeding males; L. serrator, a sawyer, a reference to the species’ saw-toothed bill.
NATURAL HISTORY Primarily winter visitors to coastal estuaries and nearshore coastal waters, Redbreasted Mergansers rarely stray inland in winter. Like all mergansers, they are adept divers that forage for small fish; they also take mollusks, crustaceans, aquatic insects, and amphibians—captured in shallow water, but they are capable of diving up to about 30 feet. This species is often overlooked inland, especially when associating with the similar-appearing Common Mergansers. Male Redbreasted Mergansers are easily distinguished by their crested heads, grayish sides, and white neck rings set off by a reddish breast. Females, juveniles, and males in nonbreeding plumage are more difficult to identify but, compared to Common Mergansers, they are smaller, with more slender necks, thinner bills, and lack the distinct white throat patches of female Common Mergansers.
STATUS AND DISTRIBUTION Red-breasted Mergansers are winter visitors and spring and fall migrants, and there are no breeding records for the Sierra region.
West Side. Casual at Lake Almanor and Lake Isabella, mostly single birds seen far from shore.
East Side. Uncommon but regular fall, winter, and spring visitors to Lake Tahoe; rare at Boca Reservoir and Prosser Creek reservoirs, and from Crowley Lake south to Owens Valley.
Ruddy Duck
Oxyura jamaicensis
ORIGIN OF NAMES Ruddy describes the bright reddish plumage of breeding males; Gr. oxyura, sharp-tailed; L. jamaicensis, of Jamaica, where the type specimen of the species was collected.
NATURAL HISTORY Stout, chunky birds with thick heads and necks, Ruddy Ducks sit low in the water, and breeding males often cock their stiff tail feathers upward. Along with other “stiff-tailed ducks,” they differ from other waterfowl in many aspects of their biology. Males wear grayishbrown plumage for most of the year and do not molt into their bright chestnut or “ruddy” breeding plumage until March, much later than other ducks. Males display startling blue bills only when breeding, and these are used as part of elaborate and distinctive courtship displays to attract prospective females. Nest building occurs from mid- to late May, and nests are large mats of aquatic plants gathered into loose, floating platforms that rise or fall with changing water levels; most are screened from above by domes of overhanging plants. Females begin laying eggs by late May, often when nests are still under construction.
Ruddy Ducks become airborne by running across open water with their short wings beating furiously. They sink out of sight rather than flying to escape danger, much like grebes and loons. Unable to walk on land, they never stray from water, and larger lakes and ponds are preferred. They forage by skimming the water’s surface and by diving in shallow water up to about three feet; favored foods include aquatic invertebrates, zooplankton, and some aquatic plants—mostly seeds and roots.
STATUS AND DISTRIBUTION Ruddy Ducks may dot the surfaces of deep lakes, reservoirs, and sewage ponds of the Sierra in spring,
