Texas Waterfowl

Red-breasted Merganser

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 128 TEXAS HARVEST There is no harvest estimate for Red-breasted Mergansers in Texas. However, harvest is likely low, as mergansers are not prized by hunters. POPULATION STATUS Red-Breasted Mergansers likely have a stable population. DIET Red-breasted Mergansers forage by diving. They find food by sight or by probing small cavities along the bottom for potential food items. They forage on a wide variety of fish, mollusks, crayfish, and large invertebrates. Gulf toadfish, sheepshead minnows, and snapping shrimp constituted 86 percent of their diet in the Laguna Madre of Texas. RANGE AND HABITATS Breeding: Red-breasted Mergansers primarily breed in the boreal forests and tundra zones of North America, Europe, and Asia. Breeding pairs are associated with coastal areas, rivers, and lakes. They nest on the ground. Nests are found in herbaceous vegetation and under brush and low-growing conifer branches. Loose colonies may develop on islands. Red-breasted Merganser (female). Photograph courtesy of Arthur Morris/VIREO, taken January 2001, Bolsa Chica Lagoon, Huntington Beach, Calif. 129 Migration and Winter: Red-breasted Mergansers migrate through interior and coastal regions of North America. Most winter in coastal regions of Alaska, Canada, Mexico, and the continental United States. They are also found in the Great Lakes, Great Salt Lake, Salton Sea, and lower stretches of the Colorado River (California). In the Laguna Madre they use sea grass beds, which harbor small fish and shrimp. REPRODUCTION Pair Bonds: Red-breasted Mergansers form seasonal pair bonds, beginning in their second winter (or later). Some females are paired by February, and pair bond formation accelerates after March. Males follow their mates to breeding locations. Pair bonds dissolve after females begin incubation. Nesting: Females line nest bowls with grass litter and down. They lay approximately 1 egg every 1–2 days, and their clutch size is about 10 eggs. Only females incubate. Their incubation period is 30–31 days. They frequently parasitize nests of other Redbreasted Mergansers. Ducklings: After ducklings leave the nest, females brood them at night and during inclement weather.The amalgamation of several broods with one female is common. Females abandon young before they can fly. Ducklings fledge in less than 65 days. APPEARANCE Breeding: Adult males have a ragged crest, and their head and back are black with a green to purple sheen. Their upper neck and rear neck are also black. The forward part of their lower neck is white. Their breast is cinnamon with black spots, and the sides of their breast are black. They have gray sides, which are separated from their iridescent back by a broad, horizontal white line. Their lower back and upper tail are gray, and their belly is white. Adult females have a rusty brown head and upper neck. Their breast is light gray, and their back and sides are gray. Their belly is white. Adult males have a red bill. Females have a bill that is orange brown with pinkish sides. Both sexes have long, narrow serrated bills. Adult males and females weigh 2.4 and 2.0 pounds, respectively. Nonbreeding: Both sexes tend to have pale, almost white lower chins but otherwise resemble adult females in breeding plumage. Immature/subadult: This plumage is acquired in their first winter. Males look like females, but some individuals may have black on their head and dark patches on their body. In females this plumage...