Greater Scaup Aythya marila Linnaeus       Field Guide IDs: NG-86; G-54; PE-58; PW-pl 11; AE-p1 124; AW-pl 93; AM(I)-178 Nest Location Nest Type Eggs & Mating System Dev. & Parental Care Primary & 2ndary Diet.. Foraging Strategy F I: 24-28 DAYS PRECOCIAL 2 FLOATING F 7-10 (5-11) MONOG F: 35-42 DAYS F AQUATIC PLANTS BREEDING: Ponds and small lakes in forested or open tundra and n border of taiga, and islands in large taiga lakes. 1 brood. DISPLAYS: See: Duck Displays. NEST: Usu concealed depression supported by tall, dead marsh grass, usu from 4" above water in swales to 50' from water on high, dry hummock. Sparsely lined with line grass and down, added to during incubation. EGGS: Dark olive buff. 2.5" (62 mm). DIET: Primarily mollusks, also other aquatic invertebrates; aquatic plants may predominate in inland freshwater habitats. CONSERVATION: Winters s to Baja. NOTES: Occ lays eggs in nests of other Greater Scaups; clutches >11 likely result from such brood parasitism. Nests occ clustered, appearing semicolonial. Male deserts when incubation begins. Females often combine broods and cooperatively tend and defend. Can dive to 20' and stay underwater 1 minute. Small to large winter flocks, occ with Lesser Scaup. STANFORD. NOTES: ESSAYS: Dabblers vs. Divers; Crèches; Parasitized Ducks; Brood Parasitism; Feathered Nests; Swimming. REFERENCES: Bellrose, 1976; Gooders and Boyer, 1986.