Canvasback Aythya valisineria Wilson       Field Guide IDs: NG-84; G-54; P-58; PW-pl 11; AE-pl 110; AW-p195;AM(I)-172 Nest Location Nest Type Eggs & Mating System Dev. & Parental Care Primary & 2ndary Diet.. Foraging Strategy F I: 24-29 DAYS PRECOCIAL 2 F 7-9 (7-12) MONOG F: 56-68 DAYS F AQUATIC INVERTS BREEDING: Open, freshwater marsh, pond, lake, river, bay, bordered by emergent veg. 1 brood. DISPLAYS: See: Duck Displays NEST: Well-concealed, rimmed, basket-shaped on bulky emergent veg over water up to knee-deep. Lined with finer materials and down. Occ uses muskrat house; rarely on dry ground. EGGS: Grayish- or greenish-olive. 2.4" (62 mm). DIET: Aquatic vegetation, aquatic invertebrates, esp. small clams. CONSERVATION: Winters s to s Mexico. Blue List 1975-81, Special Concern 1982, 1986. Draining and cultivation of prairie potholes and freshwater marshes have reduced breeding grounds. NOTES: Females highly "philopatric" (often return to natal area to breed); males virtually never do so. Mated pair never rejoin as pair in subsequent years. Male deserts when clutch complete. Nests often parasitized by Redhead. Females retain fat store during laying but lose nearly 70% during incubation. STANFORD. NOTES: ESSAYS: Blue List; Metallic Poisons; Parasitized Ducks; Dabblers vs. Divers; American Coots; Commensal Feeding; Brood Parasitism REFERENCES: Anderson, 1985; Bellrose, 1976; Gooders and Boyer, 1986; Noyes and Jarvis, 1985.