Texas Waterfowl

Common Merganser

124 COMMON MERGANSER Mergus merganser Throughout most of their range, Common Mergansers (known as Goosanders in Europe) are renowned for eating salmon. Because of this, they are often disliked by fishermen, and some countries have even experimented with programs to reduce their numbers. However, they also eat predatory fish that readily consume salmon, and there is little evidence to suggest the reduction in young salmon caused by Common Mergansers is detrimental to populations. TEXAS DISTRIBUTION Breeding: Common Mergansers are not known to breed in Texas.There are a handful of summer records, most of which are from northwestern Texas. Migration and Winter: They are most common in the High Plains and Rolling Plains, where winter concentrations of several hundred to a few thousand sometimes occur on reservoirs. They are locally common in the western Trans-Pecos and rare elsewhere. Fall migrants tend to arrive in mid-November. They begin departing Texas in late March or early April. TEXAS HARVEST Common Merganser harvest in Texas is not estimated, but it is likely small. POPULATION STATUS Common Mergansers likely have a stable population, but population estimates are poor. DIET Common Mergansers dive and hunt for food by sight.They primarily forage on fish, particularly salmon, trout, and shad. Small gizzard shad (< 4.3 inches) and threadfin shad (< 4.4 inches) were the most common fish consumed in Oklahoma and New Mexico, respectively. They occasionally consume crayfish and large aquatic insects. RANGE AND HABITATS Breeding: Common Mergansers breed in the boreal forests of North America, Europe , and Asia. In North America they also breed in forested regions of the Intermountain West and locally in western South Dakota. Breeding pairs are associated with large lakes and rivers that have mature forests nearby. They nest in tree cavities, sea ducks rock crevices, nest boxes, and holes in earthen banks (for example, riverbanks). Migration and Winter: Common Mergansers migrate throughout most of the United States. They winter in coastal regions of southern Alaska, western Canada, and southeastern Canada. They also winter throughout much of the continental United States and Mexico. They are rare to local in the southeastern United States. Wintering Common Mergansers are most common in rivers and reservoirs. REPRODUCTION Pair Bonds: Common Mergansers form pair bonds in late February. Males follow their mates north in spring. Pair bonds are seasonal, dissolving after the female begins incubation. Females likely select new mates each year. Pair bonds are not formed until their second winter (or later). Nesting: Females may carry grasses and other small items to the nest cavity if adequate materials are not already present. Down is added during egg laying. Approximately 1 egg is laid every 1–2 days. Clutch size is 9–12 eggs. Only females incubate. Their incubation period is about 32 days. They frequently parasitize nests of other Common Mergansers. Ducklings: Ducklings may remain in the nest 1–2 days after they hatch. Females provide vocal cues to encourage ducklings to exit the nest. They brood young at night and during periods of extreme weather. Young occasionally climb onto the backs of females. The period of time that females remain with ducklings is short, perhaps as brief as 7 days. Ducklings fledge at 60–75 days. APPEARANCE Breeding: Adult males have a black head and upper neck, both of which have a greenish sheen.Their lower neck, breast, and sides are white.Their back is black, and their Common Merganser (male). Photograph by Mark W. Lockwood, May 11, 2009, Hinman Lake, Colorado. 126 rump and tail are gray. Their breast and belly may be light gray or pinkish. Except for a small white chin patch, adult females have a rusty head with a shaggy crest; the rust plumage of their head continues through the middle of the neck. Their lower neck, upper breast, and body are gray.Their lower breast and belly are lighter (almost white). Males have a red bill, and females have a reddish brown bill. Both sexes have long, narrow serrated bills. Adult males and females average 3.6 and 2.7 pounds, respectively . Nonbreeding: In both males and females, this plumage is similar to the breeding plumage of adult females. However, males tend to have a shorter crest than that of females, and they may also have an olive-tinged crown. Immature/subadult: This plumage is acquired their first fall or winter. In males, the overall plumage is like that of females, but their head and neck may have black feathers . In females, this plumage is similar to their adult plumage. SOURCES introduction: Gooders and Boyer 1986; Kålås et al. 1993; McCaw et al. 1996; Marquiss and Carss 1997. texas distribution: Seyffert 2001; Lockwood and Freeman 2004. population status: Dugger et al. 1994; Sea Duck Joint Venture 2004a; Davis and Capobianco 2006. diet: Munro and Clemens 1932; Miller and Barclay 1973; Wood 1987; Kålås et al. 1993; McCaw et al. 1996; Mallory and Metz 1999. range and habitats: Bellrose 1980; Gooders and Boyer 1986; Dugger et al. 1994; Lumsden et al. 1986; Mallory and Metz 1999. reproduction: Bellrose 1980; Mallory and Lumsden Common Merganser (female). Photograph by Raymond S. Matlack, December 5, 2007, Canyon, Randall County, Texas. 127 1994; Coupe and Cooke 1999; Mallory and Metz 1999. appearance: Palmer 1976b; Bellrose 1980; Mallory and Metz 1999. RED-BREASTED MERGANSER Mergus serrator Red-breasted Mergansers often forage cooperatively. When foraging cooperatively, they form a loose line and herd fish into shallow areas. Groups feeding cooperatively may number up to 100. Snowy Egrets and other wading birds may join Red-breasted Merganser flocks once the fish are pushed into shallows. TEXAS DISTRIBUTION Breeding: There is a breeding record for Red-breasted Mergansers (two females with a brood) at Laguna Atascosa NWR in Cameron County. This is phenomenal, considering this species primarily nests in boreal forests and arctic regions. Small numbers may occur along the coast during summer. Migration and Winter: Migrants occur in East Texas and along the coast. They are rare in West Texas except for the El Paso area, where they are locally common. Wintering birds primarily occur in the Coastal Prairies, especially the Laguna Madre. Red-breasted Merganser (male). Photograph by Raymond S. Matlack, February 22, 2007, Bolivar Peninsula , Galveston County, Texas. sea ducks ...