Breeding

The following page is from the Birds of North America Mallard (Anas platyrhynchos) account. Content may or may not pertain to Mexican Duck.

Pair Formation

Majority of pairs form on wintering grounds, far in advance of breeding. Pairs form earlier (Sep–Nov) than do most Northern Hemisphere Anas species (178 Rohwer, F. C., and M. G. Anderson (1988). Female-biased philopatry, monogamy, and the timing of pair formation in migratory waterfowl. Current Ornithology 5:187–221. Close ). At Ithaca, NY, courtship begins in Sep; 90% of females paired by Nov (183 Johnsgard, P. A. (1960a). A quantitative study of sexual behavior of Mallards and Black Ducks. Wilson Bulletin 72:133-155. Close ). In coastal Louisiana, approximately 55% of migratory females arrived in Nov already paired; 95% paired by late Dec (233 Johnson, W. P. and F. C. Rohwer. (1998). Pairing chronology and agonistic behaviors of wintering Green-winged Teal and Mallards. Wilson Bulletin 110:311-315. Close ). A few new pair bonds form on spring breeding grounds, however; in Iowa, 20% of marked drakes observed with a hen initially arrived unpaired (194 Humburg, D. D., H. H. Prince and R. A. Bishop. (1978). The social organization of a Mallard population in northern Iowa. Journal of Wildlife Management 42:72-80. Close ). See 178 Rohwer, F. C., and M. G. Anderson (1988). Female-biased philopatry, monogamy, and the timing of pair formation in migratory waterfowl. Current Ornithology 5:187–221. Close for review of hypotheses on function of early pair formation in waterfowl.

Arrival On Breeding Grounds

Migrants arrive on breeding grounds as soon as open water occurs: late Feb or early Mar in southern portions of breeding range, late Mar or early Apr in midcontinent areas, mid- to late Apr in Alaska. Older hens arrive earlier in N. Dakota (average 20 Apr) than do second-year hens (average 5 May; 234 Lokemoen, J. T., H. F. Duebbert and D. E. Sharp. (1990a). Homing and reproductive habits of Mallards, Gadwalls, and Blue-winged Teal. Wildlife Monographs 106. Close ). Arrive in flocks of up to 200 birds; pairs begin to disperse a few days after arrival.

Nest-Building

Female begins searching for a nest site within 5–10 d of establishing home range. Nesting period in California begins late Feb and peaks early Apr, with few nests after early Jun; nest-initiation period (from initiation of first nest to initiation of final nest) is 40 d in northern and 66 d in central California (235 McLandress, M. R., G. S. Yarris, A. L. H. Perkins, D. P. Connelly and D. G. Raveling. (1996). Nesting biology of Mallards in California. Journal of Wildlife Management 60:94-107. Close ). At midlatitudes, nesting typically mid- or late Apr through Jun, with peak nest initiation early to mid-May. In Vermont, average date for first nest 12 Apr, nest-initiation period 10 wk, and latest initiation 6 Jun (236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ). In Iowa, first nest initiation 5–15 Apr; latest 10 Jun–3 Jul (194 Humburg, D. D., H. H. Prince and R. A. Bishop. (1978). The social organization of a Mallard population in northern Iowa. Journal of Wildlife Management 42:72-80. Close , 195 Ohde, B. R., R. A. Bishop and J. J. Dinsmore. (1983). Mallard reproduction in relation to sex ratios. Journal of Wildlife Management 47:118-126. Close ). In central Canada, first initiation 15 Apr; latest 18 Jun; 4-yr average of median dates 16 May (75 Greenwood, R. J., A. B. Sargeant, D. H. Johnson, L. M. Cowardin and T. L. Shaffer. (1995b). Factors associated with duck nest success in the Prairie Pothole Region of Canada. Wildlife Monographs 128:1-57. Close ). Nest-initiation period in N. Dakota usually spans 42–52 d but occasionally breeding continues through summer (74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close , 234 Lokemoen, J. T., H. F. Duebbert and D. E. Sharp. (1990a). Homing and reproductive habits of Mallards, Gadwalls, and Blue-winged Teal. Wildlife Monographs 106. Close , 237 Krapu, G. L. (2000). Temporal flexibility of reproduction in temperate-breeding dabbling ducks. Auk 117:640-650. Close ). Alaskan Mallards arrive and initiate nests later than midcontinent Mallards, but interval between arrival and nest initiation may be shorter (27 Bellrose, F. C. (1980). Ducks, Geese, and Swans of North America. Revised edition. Stackpole Books, Harrisburg, PA, USA. Close ).

Factors Affecting Nest Initiation

Generally, older hens begin nests before younger ones (1–2 wk; 236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ; 234 Lokemoen, J. T., H. F. Duebbert and D. E. Sharp. (1990a). Homing and reproductive habits of Mallards, Gadwalls, and Blue-winged Teal. Wildlife Monographs 106. Close , but see 74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close and 238 Anderson, M. G., J. M. Rhymer and F. C. Rohwer. (1992). "Philopatry, dispersal and the genetic structure of waterfowl populations." In Ecology and management of breeding waterfowl., edited by B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson and et al, 365-395. Minneapolis: Univ. of Minnesota Press. Close ). Spring temperatures, rainfall, and available wetlands also affect timing (75 Greenwood, R. J., A. B. Sargeant, D. H. Johnson, L. M. Cowardin and T. L. Shaffer. (1995b). Factors associated with duck nest success in the Prairie Pothole Region of Canada. Wildlife Monographs 128:1-57. Close ). Low spring temperatures can delay nesting for up to 2 wk (68 Sowls, L. K. (1955). Prairie ducks: A study of their behavior, ecology and management. Washington, D.C: Stackpole Co., Harrisburg, PA, and Wildl. Manage. Inst. Close , 236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ). In prairie Canada, nest initiation started 2.3 d later for each 1°C decrease in average May temperature, and nest-initiation interval extended by 0.1 d for each 1 cm increase in average May precipitation (75 Greenwood, R. J., A. B. Sargeant, D. H. Johnson, L. M. Cowardin and T. L. Shaffer. (1995b). Factors associated with duck nest success in the Prairie Pothole Region of Canada. Wildlife Monographs 128:1-57. Close ). In N. Dakota, peak nesting activity delayed 2.2 d/1°C drop in average Apr temperature (74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close ). In California, timing of nest initiation positively correlated with early-spring precipitation but not with spring temperatures (235 McLandress, M. R., G. S. Yarris, A. L. H. Perkins, D. P. Connelly and D. G. Raveling. (1996). Nesting biology of Mallards in California. Journal of Wildlife Management 60:94-107. Close ). Drought strongly affects nesting: in N. Dakota; period of nest initiation lasts 85 d during average year but only 66 d during severe drought (239 Krapu, G. L., A. T. Klett and D. G. Jorde. (1983). The effect of variable spring water conditions on Mallard reproduction. Auk 100:689-698. Close ).

First Brood Per Season

Figure 2 . First egg laid approximately 1–4 d after nest-site selection.

Renesting

Commonly renests if first clutch destroyed or abandoned; renesting dependent on incubation stage and date of nest loss. In Vermont, 57% of 30 marked hens that lost their first clutches renested (236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ). In Manitoba, 76% (n = 21) renested after nest destroyed by predators; 1 female renested 5 times and 3 renested 3 times (240 Rotella, J. J., D. W. Howerter, T. P. Sankowski and J. H. Devries. (1993). Nesting effort by wild Mallards with 3 types of radio transmitters. Journal of Wildlife Management 57:690-695. Close ). Estimated renesting rates 8–30% in 9 other studies (interpreting data in 241 Cowardin, L. M. and D. H. Johnson. (1979). Mathematics and Mallard management. Journal of Wildlife Management 43:18-35. Close ). First-year females less likely to renest, but several reports of postyearling females producing up to 4 clutches per season in the wild and experimentally induced to produce up to 5 clutches (reviewed in 242 Swanson, G. A., T. L. Shaffer, J. F. Wolf and F. B. Lee. (1986). Renesting characteristics of captive Mallards on experimental ponds. Journal of Wildlife Management 50:32-38. Close ). Wild Mallards rarely renest after a brood loss, but urban Mallards do so frequently (86 Figley, W. K. and L. W. VanDruff. (1982). Ecology of urban Mallards. Wildlife Monographs 81:1-39. Close ). Hens rely more on available food resources than on lipid reserves for renesting (36 Krapu, G. L. (1981). The role of nutrient reserves on Mallard reproduction. Auk 98:29-38. Close , 120 Krapu, G. L. and K. J. Reinecke. (1992). "Foraging ecology and nutrition." In Ecology and management of breeding waterfowl., edited by B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec, G. L. Krapu and R. Sayler, 1-29. Minneapolis: Univ. Minnesota Press. Close ). Thus, preva-lence of renesting dependent on spring and summer temperatures, precipitation, and availability and condition of wetlands (120 Krapu, G. L. and K. J. Reinecke. (1992). "Foraging ecology and nutrition." In Ecology and management of breeding waterfowl., edited by B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec, G. L. Krapu and R. Sayler, 1-29. Minneapolis: Univ. Minnesota Press. Close , 75 Greenwood, R. J., A. B. Sargeant, D. H. Johnson, L. M. Cowardin and T. L. Shaffer. (1995b). Factors associated with duck nest success in the Prairie Pothole Region of Canada. Wildlife Monographs 128:1-57. Close ).

Renesting interval of captive birds 7.1 d (range 5–10); food deprivation lengthened interval between nest loss and initiation of renest in captive hens (242 Swanson, G. A., T. L. Shaffer, J. F. Wolf and F. B. Lee. (1986). Renesting characteristics of captive Mallards on experimental ponds. Journal of Wildlife Management 50:32-38. Close ). Some have reported a positive correlation between stage of incubation at nest loss and renesting interval; in theory, as ovarian follicles regress during incubation, time required to regenerate them increases. Sowls (68 Sowls, L. K. (1955). Prairie ducks: A study of their behavior, ecology and management. Washington, D.C: Stackpole Co., Harrisburg, PA, and Wildl. Manage. Inst. Close ) reported an increase in the interval by 0.6 d for each day into incubation. Others have found no correlation, however, and time to renesting may depend on a variety of environmental factors as well as individual variation (236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ).

Second/Later Broods Per Season

Wild Mallards rarely raise second broods, but some birds in urban and unnaturally crowded populations may. In a crowded Manitoba population, 22 hens renested after having hatched ducklings from their first brood; 11 of these hens left live prefledged broods to renest (193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close ).

Nonbreeding Nests

Not known to occur.

Selection

Begins searching for nest site within few days of selecting breeding home range, generally 5–10 d after first Persistent Quacking by hen. Pair searches by making low circling flights over the area, usually in evening; alight and female walks into cover; male walks nearby or waits outside cover. Female makes several scrapes during days before first egg laid.

Microhabitat; Site Characteristics

Usually nests on ground in upland area near water; nest placed under overhanging cover or in dense vegetation for maximum concealment. Shifts preferences as season progresses and more cover develops (74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close ). Grassland cover includes whitetop (Scholochloa festucacea), buckbrush (Symphoricarpos orbiculatus), cordgrass (Spartina spp.), saltbush (Atriplex spp.), nettle (Urtica spp.), thistles, prairie grass, and shrubs. In midcontinent prairie habitats, often uses western snowberry (Symphoricarpos occidentalis) and Wood's rose (Rosa woodsii) more frequently than available (74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close , 243 Duebbert, H. F., J. T. Lokemoen and D. E. Sharp. (1986). Nest sites of ducks in grazed mixed-grass prairie in North Dakota. Prairie Naturalist 18:99-108. Close ). In n. California, nests in saltbush and nettle more frequently than available and in grass less frequently (244 Miller, A. W. and B. D. Collins. (1954). A nesting study of ducks and coots on Tule Lake and Lower Klamath National Wildlife Refuge. California Fish and Game 40:17-37. Close ). Growing alfalfa (Medicago sativa) highly attractive after it reaches half its mature height and density (74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close ). Although less common, will nest in other agricultural fields such as winter wheat, barley, flax (Linum sp.), and oats, if cover sufficient (245 Earl, J. P. (1950). Production of Mallards on irrigated land in the Sacramento Valley, California. Journal of Wildlife Management 14:332-342. Close , 246 Higgins, K. F. (1977). Duck nesting in intensively farmed areas of North Dakota. Journal of Wildlife Management 41:232-242. Close ). Average height of vegetation at Saskatchewan nest sites 59–71 cm (70 Clark, R. G. and D. Shutler. (1999). Avian habitat selection: pattern from process in nest-site use by ducks? Ecology 80:272-287. Close ) and ≤1 m in brush/grass habitats in prairie parklands region (75 Greenwood, R. J., A. B. Sargeant, D. H. Johnson, L. M. Cowardin and T. L. Shaffer. (1995b). Factors associated with duck nest success in the Prairie Pothole Region of Canada. Wildlife Monographs 128:1-57. Close ). In n. California, 82% of nests in vegetation <60 cm (244 Miller, A. W. and B. D. Collins. (1954). A nesting study of ducks and coots on Tule Lake and Lower Klamath National Wildlife Refuge. California Fish and Game 40:17-37. Close ).

In forests, uses low woody cover, fallen logs, stands of dense saplings, dead tree tops, hollow base of trees, abandoned raptor or crow nests, and herbaceous growth. In Vermont, 28% of nests in low dead herbaceous plants and 19% in live conifers (236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ). Nests in Minnesota found in leatherleaf (Chamaedaphne calyculata) and Labrador tea (Ledum groenlandicum) and in stems of slender willow (Salix gracilis) and speckled alder (Alnus rugosa; 61 Gilmer, D. S., I. J. Ball, L. M. Cowardin, J. H. Riechmann and J. R. Tester. (1975). Habitat use and home range of Mallards breeding in Minnesota. Journal of Wildlife Management 39:781-789. Close ).

Although Mallard usually an upland nester, more likely than other dabbling ducks to nest in wetlands or over water. Cover vegetation at overwater and wetland nest sites includes reedgrass (Phragmites spp.), bulrush, cat-tail, slough sedge (Beckmannia syzigachne) and grass (73 Krapu, G. L., L. G. Talent and T. J. Dwyer. (1979b). Marsh nesting by Mallards. Wildlife Society Bulletin 7:104-110. Close ). In N. Dakota, 47% of wetland nest sites in bulrush and 17% in cat-tail (74 Cowardin, L. M., D. S. Gilmer and C. W. Shaiffer. (1985). Mallard recruitment in the agricultural environment of North Dakota. Wildlife Monographs 92:1-37. Close ); in s. Alberta, 70% of nests in Juncus wetlands (129 Keith, L. B. (1961). A study of waterfowl ecology on small impoundments in southeastern Alberta. Wildlife Monographs 6. Close ). In N. Dakota, average height of emergent vegetation at overwater nests 76.7 cm ± 25.4 SD (73 Krapu, G. L., L. G. Talent and T. J. Dwyer. (1979b). Marsh nesting by Mallards. Wildlife Society Bulletin 7:104-110. Close ). See also Habitat: breeding, above.

Urban Mallards use variety of additional cover types, including evergreens, ornamental shrubs, vines, gardens, woodpiles, and artificial structures such as docks and boats (86 Figley, W. K. and L. W. VanDruff. (1982). Ecology of urban Mallards. Wildlife Monographs 81:1-39. Close ). Both urban and wild populations readily nest in artificial nesting structures (153 Doty, H. A. and F. B. Lee. (1974). Homing to nest baskets by wild female Mallards. Journal of Wildlife Management 38:714-719. Close , 193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close ).

Construction Process; Structure And Composition Matter

From 247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close and 11 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close . Hen forms shallow depression or bowl on ground in moist earth by dropping forward onto her breast and digging into ground with feet while rotating to form bowl. Does not carry material to nest but rather uses what she can reach and pull toward her with bill while sitting on nest. During laying phase, bowl lined with vegetation and plant litter from nearby, including grasses, leaves, and twigs. Hen also pulls and bends tall vegetation over to conceal herself and nest. After incubation begins, plucks down from breast to line nest and cover eggs. Overwater nests range from simple bowls on floating vegetation mats to elaborate structures woven into emergent vegetation (73 Krapu, G. L., L. G. Talent and T. J. Dwyer. (1979b). Marsh nesting by Mallards. Wildlife Society Bulletin 7:104-110. Close ).

Dimensions

Outside diameter 26–29 cm; inside diameter 14–22 cm, nest bowl depth 2.5–14 cm (95 Cramp, S., and K. E. L. Simmons, Editors (1977). The Birds of the Western Palearctic. Volume 1. Ostrich to Ducks. Oxford University Press, Oxford, UK. Close , 27 Bellrose, F. C. (1980). Ducks, Geese, and Swans of North America. Revised edition. Stackpole Books, Harrisburg, PA, USA. Close ).

Microclimate

Temperatures in nest high enough for development of embryo as early as sixth egg laid. Average nest-air temperature of 3 Manitoba nests during incubation 31.2°C; average nest-bottom temperature 23.1°C ± 5.8 SD (n = 235) during early days of incubation and gradually increases to 27.5°C ± 8.4 SD, n = 284) days later (247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close ). In 32 Saskatchewan nests, nest temperatures <25°C 86% of time, and nest site temperature rarely >38°C (248 Gloutney, M. L. and R. G. Clark. (1997). Nest-site selection by Mallards and Blue-winged Teal in relation to microclimate. Auk 114:381-395. Close ). Hens may choose sites that provide protection from sun; in Saskatchewan, nests received less solar insolation than random sites between hours of 05:30 and 21:30 and operative temperature at nest sites averaged 5°C cooler than random sites between 08:00 and 17:30 (248 Gloutney, M. L. and R. G. Clark. (1997). Nest-site selection by Mallards and Blue-winged Teal in relation to microclimate. Auk 114:381-395. Close ). At same site, humidity levels did not differ significantly between nests and random sites. Humidity in 2 nests measured 17.4 and 26.7 Torr (249 Afton, A. D., and S. L. Paulus (1992). Incubation and brood care. In Ecology and Management of Breeding Waterfowl (B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, et al., Editors), University of Minnesota Press, Minneapolis, Minnesota, USA. pp. 62–108. Close ).

Maintenance Or Reuse Of Nests

Throughout laying and incubation, hen reshapes and adds vegetation and down to nest bowl. In case of nest failure, renesting female does not reuse old nest; however, in Manitoba, usually renests within 120–250 m (68 Sowls, L. K. (1955). Prairie ducks: A study of their behavior, ecology and management. Washington, D.C: Stackpole Co., Harrisburg, PA, and Wildl. Manage. Inst. Close ), and in Vermont, 65% renest within 120 m of original nest (236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ). One report of nest reuse: 73% of Mallard nests in previously used bowls in a concentrated island population in N. Dakota (250 Duebbert, H. F., J. T. Lokemoen and D. E. Sharp. (1983). Concentrated nesting of Mallards and Gadwall on Miller Lake Island, North Dakota. Journal of Wildlife Management 47:309-321. Close ).

Shape

Elliptical to subelliptical or blunt oval (251 Bent, A. C. (1923). Life histories of North American wildfowl: Order Anseres (Part 1). United States National Museum Bulletin 126. Close , 11 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close ).

Size

Dimensions (length x width in mm) in North America: 57.8 × 41.6 (range 52.5–64 × 38.5–45, n = 93; various museum collections, 251 Bent, A. C. (1923). Life histories of North American wildfowl: Order Anseres (Part 1). United States National Museum Bulletin 126. Close ), 56.5 ± 2.1 × 41.1 ± 1.4 SD (range 5.12–59.5 × 3.84–43.7, n = 62, 7 clutches; Minnesota and N. Dakota; Bell Museum of Natural History, ND).

Egg size heritable (egg mass heritability 0.55; 252 Prince, H. H., P. B. Siegel and G. W. Cornwell. (1970). Inheritance of egg production and juvenile growth in Mallards. Auk 87:342-352. Close ) but strongly influenced by habitat condition, food quality, hen condition, and population density (253 Eldridge, J. L. and G. L. Krapu. (1988). The influence of diet quality on clutch size and laying pattern in Mallards. Auk 105:102-110. Close , 254 Pehrsson, O. (1991). Egg and clutch size in the Mallard as related to food quality. Canadian Journal of Zoology 69:156-162. Close , 120 Krapu, G. L. and K. J. Reinecke. (1992). "Foraging ecology and nutrition." In Ecology and management of breeding waterfowl., edited by B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec, G. L. Krapu and R. Sayler, 1-29. Minneapolis: Univ. Minnesota Press. Close ).

Mass

Average (in g) in North America: 52.2 ± 4.2 SD (n = 1,085 [Manitoba captive wild strain]; 190 Rhymer, J. M. (1988). The effect of egg size variability on thermoregulation of Mallard (Anas platyrhynchos) offspring and its implications for survival. Oecologia 75:20-24. Close ), 52.2 (range 32.2–66.7, n = 613 [N. Dakota captive wild strain]; 253 Eldridge, J. L. and G. L. Krapu. (1988). The influence of diet quality on clutch size and laying pattern in Mallards. Auk 105:102-110. Close ), 52.2 (n = 455 [California]; 254 Pehrsson, O. (1991). Egg and clutch size in the Mallard as related to food quality. Canadian Journal of Zoology 69:156-162. Close ), 52.5 (n = 595 [Manitoba]; 254 Pehrsson, O. (1991). Egg and clutch size in the Mallard as related to food quality. Canadian Journal of Zoology 69:156-162. Close ), 49.3 ± 3.5 SD (n = 27 [N. Dakota]; Lokemoen et al. 37 Lokemoen, J. T., D. H. Johnson and D. E. Sharp. (1990b). Weights of wild Mallard Anas platyrhynchos, Gadwall A. strepera, and Blue-winged Teal A. discors during the breeding season. Wildfowl 41:122-130. Close ). Variation among clutches high-er than variation within clutches (255 Birkhead, M. (1985a). Variation in egg quality and composition in the Mallard Anas platyrhynchos. Ibis 127:467-475. Close , 190 Rhymer, J. M. (1988). The effect of egg size variability on thermoregulation of Mallard (Anas platyrhynchos) offspring and its implications for survival. Oecologia 75:20-24. Close ). In captive wild-type hens, egg mass increases with each renest; 0.43 g heavier/nest attempt within hens (256 Batt, B. D. J. and H. H. Prince. (1979). Laying dates, clutch size and egg weights of captive Mallards. Condor 81:35-41. Close , 253 Eldridge, J. L. and G. L. Krapu. (1988). The influence of diet quality on clutch size and laying pattern in Mallards. Auk 105:102-110. Close ).

Color

Varies from creamy to grayish or greenish buff; no markings (Bent, 251 Bent, A. C. (1923). Life histories of North American wildfowl: Order Anseres (Part 1). United States National Museum Bulletin 126. Close , 11 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close ).

Surface Texture

Smooth and waxy.

Eggshell Thickness

No information.

Clutch Size

Range 1–13 eggs; if greater, assumed to be result of egg-dumping (11 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close , 254 Pehrsson, O. (1991). Egg and clutch size in the Mallard as related to food quality. Canadian Journal of Zoology 69:156-162. Close , 138 Alisauskas, R. T., and C. D. Ankney (1992). The cost of egg laying and its relationship to nutrient reserves in waterfowl. In Ecology and Management of Breeding Waterfowl (B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec and G. L. Krapu, Editors), University of Minnesota Press, Minneapolis, Minnesota, USA. pp. 30–61. Close ). Average clutch size of 20 North American studies between 1949 and 1957: 8.72, (range of means 5.7–10.6, n = 1,468; 67 Dzubin, A. and J. B. Gollop. (1972). "Aspects of Mallard breeding ecology in Canadian parkland and grassland." In Population ecology of migratory birds, 113-152. U.S. Fish Wildl. Serv. Rep. no. 2. Close : Appendix B). Clutch size influenced by nest-initiation date, quality of available diet, and hen's condition (256 Batt, B. D. J. and H. H. Prince. (1979). Laying dates, clutch size and egg weights of captive Mallards. Condor 81:35-41. Close , 253 Eldridge, J. L. and G. L. Krapu. (1988). The influence of diet quality on clutch size and laying pattern in Mallards. Auk 105:102-110. Close , 138 Alisauskas, R. T., and C. D. Ankney (1992). The cost of egg laying and its relationship to nutrient reserves in waterfowl. In Ecology and Management of Breeding Waterfowl (B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec and G. L. Krapu, Editors), University of Minnesota Press, Minneapolis, Minnesota, USA. pp. 30–61. Close ). Clutch size declines throughout season; a combination of decrease of clutch size of first nests with season (e.g., 0.027 egg/d, N. Dakota; 234 Lokemoen, J. T., H. F. Duebbert and D. E. Sharp. (1990a). Homing and reproductive habits of Mallards, Gadwalls, and Blue-winged Teal. Wildlife Monographs 106. Close ) and decrease with each renesting effort (e.g., average first clutch 10.4 ± 0.2 SE [n = 151], average fourth clutch 8.2 ± 0.8 [n = 13], captive wild-type hens; 256 Batt, B. D. J. and H. H. Prince. (1979). Laying dates, clutch size and egg weights of captive Mallards. Condor 81:35-41. Close ). Similar results in Vermont study of wild Mal-lards; average size of first clutch (10.6) 1.0 egg more than average clutch size of renests (9.6; n = 15; 236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ). Diet has impact; in captive wild-type sibling pairs, sibling fed enriched diet had higher clutch size, larger eggs, faster laying rate, and more nesting attempts (253 Eldridge, J. L. and G. L. Krapu. (1988). The influence of diet quality on clutch size and laying pattern in Mallards. Auk 105:102-110. Close ). Average clutch size declined from 9.8 during a year with average precipitation in N. Dakota to 9.1 in a drought year (1977; 239 Krapu, G. L., A. T. Klett and D. G. Jorde. (1983). The effect of variable spring water conditions on Mallard reproduction. Auk 100:689-698. Close ) but did not vary with pond density (1966–1981) or local water conditions (1988–1994; 257 Pietz, P. J., G. L. Krapu, D. A. Buhl and D. A. Brandt. (2000). Effects of water conditions on clutch size, egg volume, and hatchling mass of Mallards and Gadwalls in the Prairie Pothole Region. Condor 102:936-940. Close ).

Egg-Laying

Time between nest-building and laying of first egg 1–3 d in Vermont (236 Coulter, M. W. and W. R. Miller. (1968). Nesting biology of Black Ducks and Mallards in northern New England. Vt. Fish Game Bull. 38 (2):1-73. Close ), 6 d in Manitoba (68 Sowls, L. K. (1955). Prairie ducks: A study of their behavior, ecology and management. Washington, D.C: Stackpole Co., Harrisburg, PA, and Wildl. Manage. Inst. Close ). Usually 1 egg laid/d and laying females spend a few minutes to an hour on nest. Egg usually laid in morning. At each egg-laying visit, hen adds nesting material and reshapes bowl.

Egg-dumping occurs occasionally under crowding: 21% of 267 Mallard nests had eggs from ≥2 Mal-lard hens (193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close ), and 8% of small island nests (n = 389) had >13 eggs (250 Duebbert, H. F., J. T. Lokemoen and D. E. Sharp. (1983). Concentrated nesting of Mallards and Gadwall on Miller Lake Island, North Dakota. Journal of Wildlife Management 47:309-321. Close ). Mallard eggs also reported in nests of Northern Pintails, Cinnamon Teal, Canvasbacks, Redheads (Aythya americana), and Ruddy Ducks (Oxyura jamaicensis; 258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close ).

Onset Of Broodiness And Incubation In Relation To Laying

Incubation begins during egg-laying period; time spent on nest gradually increases with each egg laid. Nest temperatures adequate for embryonic development reached by sixth egg laid in average clutch of 10. Hen spends average of 13 daylight hours on nest after midpoint of egg-laying. Almost no incubation at night until after clutch is complete. See 247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close .

Incubation Patch

From 247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close . Female has 1 incubation patch (not true brood patch)—some bareness on breast and upper belly as result of plucking down to line nest. Hen “quivers” when settling onto nest to push feathers down around eggs for incubation. Patch temperature of domestic Mallards about 39.5°C; estimated temperature in wild Mallards approximately 39°C. Incubating deep-body temperature 41°C.

Incubation Period

Average incubation period 28 d, normal range 23–30 (11 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close and references therein).

Parental Behavior

From 259 McKinney, F. (1952). Incubation and hatching behavior in the Mallard. Wildfowl 5:68-70. Close and 247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close , unless indicated otherwise. Only hen incubates. Usually leaves nest once in early morning, returning before 9:00 and once in late afternoon, leaving after 16:00 (260 Gloutney, M. L., R. G. Clark, A. D. Afton and G. J. Huff. (1993). Timing of nest searches for upland nesting waterfowl. Journal of Wildlife Management 57:597-601. Close ). If pair bond still intact, drake accompanies her on recess. Dominant activities during recess are foraging and preening (159 Titman, R. D. (1981). A time-activity budget for breeding Mallards (Anas platyrhynchos) in Manitoba. Canadian Field-Naturalist 95:266-271. Close ). When leaving for recess, hen covers eggs with down; when returns, adds material and reshapes nest. Recess lasts 15–60 min (average 24 min). Frequency and length of recesses depend on weather. Positive correlation between air temperature and recess duration but, during hot weather, hen may only recess in late afternoon.

Overall, hen spends average of 22.7 h/d on nest. Throughout incubation, hen rises to turn eggs, changing her position on eggs every 15–60 min (average 35 min). Hen uses underside of chin and bill to turn eggs, or rotates eggs by paddling feet and waggling side to side. When turning, moves outer eggs in and pushes inner eggs to outside; eggs usually turned along long axis.

As incubation progresses, hen flushes from nest at shorter distances (193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close , 229 Forbes, M. R. L., R. G. Clark, P. J. Weatherhead and T. Armstrong. (1994). Risk-taking by female ducks: intra- and interspecific tests of nest defense theory. Behavioral Ecology and Sociobiology 34:79-85. Close ). Abandonment during incubation rare in most situations, but is common under crowding (29%; 193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close ) and in urban populations (17%; 86 Figley, W. K. and L. W. VanDruff. (1982). Ecology of urban Mallards. Wildlife Monographs 81:1-39. Close ).

Hardiness Of Eggs Against Temperature Stress; Effect Of Egg Neglect

Freshly laid eggs cold tolerant; embryos more tolerant of cold than heat. Egg temperatures rise slowly throughout incubation and reach 38.7°C in final days. Average internal egg temperature 36.3°C for days 1–24 of incubation. Average egg-cooling rate in nest, when not being incubated during recess, 0.64°C/1°C/h (average ambient temperature 15.8°C). See 247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close for details.

Ducklings begin vocalizing from within egg 24 h before first sign of break in shell (pipping). Hen responds with quiet calls and increasing egg-turning. Pipping lasts 3–36 h. First egg laid is first to hatch, and others usually follow within 6–10 h. Most eggs hatch during the day (261 Bjarvall, A. (1968). The hatching and nest-exodus behaviour of Mallard. Wildfowl 19:70-80. Close ). Hen oils her breast and belly feathers, and thereby the ducklings, during hatch and continues to brood clutch until all hatch. See 259 McKinney, F. (1952). Incubation and hatching behavior in the Mallard. Wildfowl 5:68-70. Close and 247 Caldwell, P. J. and G. W. Cornwell. (1975). Incubation behavior and temperatures of the Mallard duck. Auk 92:706-731. Close for details.

Condition At Hatching

Ducklings hatch fully covered with down; dry in about 12 h. Begin moving around nest when dry, alternating short periods of high activity and long periods of rest. May wander up to 1 m from nest, always maintaining contact with hen with Contentment or Distress calls. Gradually become more mobile and steady within 24 h of hatching (261 Bjarvall, A. (1968). The hatching and nest-exodus behaviour of Mallard. Wildfowl 19:70-80. Close ). Ducklings brooded by hen until nest departure. Some ability to maintain body temperature at hatching; near homeothermic at 24 h posthatch (262 Caldwell, P. J. (1973). Development of thermoregulation in Mallard ducklings. Condor 75:113-114. Close ). Egg tooth lost soon after hatching.

Average duckling mass at 24 h in North America: 31.8 g (range 27.2–40.6, n = 27; Alberta, Manitoba, Minnesota; 17 Nelson, C. H. (1992). The Downy Waterfowl of North America. Delta Station Press, Deerfield, Illinois, USA. Close ), 34.1 g ± 3.1 SD (range for brood means 27.2–42.9, n = 83 broods; N. Dakota, Minnesota; P. J. Pietz and G. Krapu unpubl.), 32.4 g ± 2.4 SD (n = 36; N. Dakota; 37 Lokemoen, J. T., D. H. Johnson and D. E. Sharp. (1990b). Weights of wild Mallard Anas platyrhynchos, Gadwall A. strepera, and Blue-winged Teal A. discors during the breeding season. Wildfowl 41:122-130. Close ). Duckling mass significantly and positively correlated with egg mass (256 Batt, B. D. J. and H. H. Prince. (1979). Laying dates, clutch size and egg weights of captive Mallards. Condor 81:35-41. Close , 253 Eldridge, J. L. and G. L. Krapu. (1988). The influence of diet quality on clutch size and laying pattern in Mallards. Auk 105:102-110. Close , 190 Rhymer, J. M. (1988). The effect of egg size variability on thermoregulation of Mallard (Anas platyrhynchos) offspring and its implications for survival. Oecologia 75:20-24. Close ). Average short tarsus length 22.0 mm ± 0.98 SD (n = 33) and average long tarsus length 25.0 mm ± 1.20 SD (range 22.00–27.60, n = 45; 17 Nelson, C. H. (1992). The Downy Waterfowl of North America. Delta Station Press, Deerfield, Illinois, USA. Close ).

Departure From Nest

Ducklings usually depart on morning after hatching, depending on weather. Most ducklings 13–16 h old at departure (261 Bjarvall, A. (1968). The hatching and nest-exodus behaviour of Mallard. Wildfowl 19:70-80. Close ). Hen vocalizes up to 200 times/min and brood follows her to water (261 Bjarvall, A. (1968). The hatching and nest-exodus behaviour of Mallard. Wildfowl 19:70-80. Close ). Distance moved by broods from nest to water ranged from 45 to 3,076 m in Manitoba (263 Rotella, J. J. and J. T. Ratti. (1992a). Mallard brood movements and wetland selection in southwestern Manitoba. Journal of Wildlife Management 56:508-515. Close ). First pond used by brood not necessarily the nearest water; only 37% of hens moved to nearest water in Saskatchewan (69 Dzus, E. H. and R. G. Clark. (1997). Overland travel, food abundance, and wetland use by Mallards: relationships with offspring survival. Wilson Bulletin 109:504-515. Close ).

Growth And Development

In S. Dakota, downy stage approximately ages 1–25 d, mixed down and feather stage 25–46 d, and preflight feathered stage 46–60 d (26 Gollop, J. B. and W. H. Marshall. (1954). A guide for aging duck broods in the field. St. Paul, MN: Mississippi Flyway Council, Tech. Sec. Rep. Close ). Young birds can fly at age 52–70 d, although schedule appears advanced by up to 10 d in Alaska (11 Palmer, R. S. (1976). Handbook of North American Birds, Volume 2: Waterfowl. Part 1. Yale University Press, New Haven, Connecticut, USA. Close , 27 Bellrose, F. C. (1980). Ducks, Geese, and Swans of North America. Revised edition. Stackpole Books, Harrisburg, PA, USA. Close ).

Mass at hatching doubles in 1 wk and quadruples in 2 wk (264 Kear, J. (1965). The internal food reserves of hatching Mallard ducklings. Journal of Wildlife Management 29:523-528. Close ). In N. Dakota, mean brood mass at age 16 d positively related to aquatic invertebrate numbers and negatively related to variance in daily minimum air temperature (265 Cox, R. R., Jr., M. A. Hanson, C. C. Roy, N. H. Euliss, D. H. Johnson and M. G. Butler. (1998a). Mallard duckling growth and survival in relation to aquatic invertebrates. Journal of Wildlife Management 62:124-133. Close ). Maximum growth rate at 2.5 wk. Mass approaches asymptote around 60 d and often decreases slightly at fledging (266 Sugden, L. G., E. A. Driver and M. C. S. Kingsley. (1981). Growth and energy consumption by captive Mallards. Canadian Journal of Zoology 59:1567-1570. Close , 37 Lokemoen, J. T., D. H. Johnson and D. E. Sharp. (1990b). Weights of wild Mallard Anas platyrhynchos, Gadwall A. strepera, and Blue-winged Teal A. discors during the breeding season. Wildfowl 41:122-130. Close ). Duckling daily growth rate 0.0692 (logistic growth curve; 37 Lokemoen, J. T., D. H. Johnson and D. E. Sharp. (1990b). Weights of wild Mallard Anas platyrhynchos, Gadwall A. strepera, and Blue-winged Teal A. discors during the breeding season. Wildfowl 41:122-130. Close ) and maximum relative growth rate/wk is 0.119 for females and 0.192 for males (Gompertz growth curve; 266 Sugden, L. G., E. A. Driver and M. C. S. Kingsley. (1981). Growth and energy consumption by captive Mallards. Canadian Journal of Zoology 59:1567-1570. Close ). In 2 different studies, average duckling mass at end of week 1 of life was 66 g ± 9.7 SD and 71.7 g; week 2, 148 g ± 14.4 SD and 196.8 g; week 3, 288 g ± 24.6 SD and 379.4 g; week 4, 388 g ± 46.0 SD and 571.9 g; week 5, 453 g ± 58.4 SD and 742.1 g; and week 6, 683 g ± 46.8 SD and 871.2 g (hatchery hatched from Manitoba wild eggs; 267 Southwick, C. (1953). A system of age classification for field studies of waterfowl broods. Journal of Wildlife Management 17:1-8. Close , 266 Sugden, L. G., E. A. Driver and M. C. S. Kingsley. (1981). Growth and energy consumption by captive Mallards. Canadian Journal of Zoology 59:1567-1570. Close ). Birds reach adult size in 4–6 mo.

Control of Body Temperature. Becomes endo-thermic around 24 h of age but cannot maintain body temperatures for extended periods of time and requires brooding until approximately 2 wk old (Caldwell 262 Caldwell, P. J. (1973). Development of thermoregulation in Mallard ducklings. Condor 75:113-114. Close , 190 Rhymer, J. M. (1988). The effect of egg size variability on thermoregulation of Mallard (Anas platyrhynchos) offspring and its implications for survival. Oecologia 75:20-24. Close ). Requires frequent brooding at night and during cold weather. See Demography and populations: causes of mortality, below.

Brood Habitat Use

Uses seasonal, semipermanent, or permanent ponds, lakes and lagoons, rivers, and creeks. Habitat used by broods varies among regions, years, and individuals; sometimes broods use habitat types in relation to availability and other times do not (for summaries of prairie habitat, see 27 Bellrose, F. C. (1980). Ducks, Geese, and Swans of North America. Revised edition. Stackpole Books, Harrisburg, PA, USA. Close and 263 Rotella, J. J. and J. T. Ratti. (1992a). Mallard brood movements and wetland selection in southwestern Manitoba. Journal of Wildlife Management 56:508-515. Close ;. for forested habitats see 63 Rempel, R. S., K. F. Abraham, T. R. Gadawski, S. Gabor and R. K. Ross. (1997). A simple wetland habitat classification for boreal forest waterfowl. Journal of Wildlife Management 61 (3):746-757. Close and 65 Carriere, S. and R. D. Titman. (1998). Habitat use by sympatric Mallard Anas platyrhynchos and American Black Duck A. rubripes broods in a forested area of Quebec, Canada. Wildfowl 49:150-160. Close ). Tends to use water edge or shallow water areas and wetlands with both emergent vegetation and open water (e.g., 268 Mauser, D. M., R. L. Jarvis and D. S. Gilmer. (1994a). Movements and habitat use of Mallard broods in northeastern California. Journal of Wildlife Management 58:88-94. Close ).

Broods frequently switch ponds; may move 12 times before fledging; usually move only once/d, become less mobile after first week (69 Dzus, E. H. and R. G. Clark. (1997). Overland travel, food abundance, and wetland use by Mallards: relationships with offspring survival. Wilson Bulletin 109:504-515. Close ). Average distance moved during first week of life 124 m/d in Manitoba (263 Rotella, J. J. and J. T. Ratti. (1992a). Mallard brood movements and wetland selection in southwestern Manitoba. Journal of Wildlife Management 56:508-515. Close ). May move extremely long distances; 1 brood moved 4.8 km in 1 wk and 8 km in 9 d in Saskatchewan (67 Dzubin, A. and J. B. Gollop. (1972). "Aspects of Mallard breeding ecology in Canadian parkland and grassland." In Population ecology of migratory birds, 113-152. U.S. Fish Wildl. Serv. Rep. no. 2. Close ). Mean cumulative brood home range in N. Dakota 11 ha (range 4–20 ha; 226 Talent, L. G., R. L. Jarvis and G. L. Krapu. (1983). Survival of Mallard broods in south-central North Dakota. Condor 85:74-78. Close ) and 0.93 km²± 0.25 SE in n. California (268 Mauser, D. M., R. L. Jarvis and D. S. Gilmer. (1994a). Movements and habitat use of Mallard broods in northeastern California. Journal of Wildlife Management 58:88-94. Close ).

Duckling Feeding

Begins pecking at dark spots and small objects as soon as it leaves nest. Although proportion of time spent feeding differs little among ages, feeding rate increases with age: rate averages 11.1 efforts/min in ducklings 1–6 d old and 22.2 efforts/min at 46–55 d (269 Pehrsson, O. (1979). Feeding behavior, feeding habitat utilization, and feeding efficiency of Mallard ducklings (Anas platyrhynchos L.) as guided by a domestic duck. Vitrevy 10:193-218. Close , 270 Ringelman, J. K. and L. D. Flake. (1980). Diurnal visibility and activity of Blue-winged Teal and Mallard broods. Journal of Wildlife Management 44:822-829. Close ).

Ducklings <25 d old eat mostly animal foods (invertebrates, small crustacea, mollusks, and fish eggs), especially chironomids. Animal food made up 61% of esophageal contents in England (271 Street, M. (1977). The food of Mallard ducklings in a wet gravel quarry and its relation to duckling survival. Wildfowl 28:113-125. Close ) and 90% in Utah (272 Chura, N. J. (1961). Food availability and preferences of juvenile Mallards. Transactions of the North American Wildlife and Natural Resources Conference 26:121-134. Close ). During this period, mostly catches invertebrates on water surface or on land; also frequently leaps to catch flying insects or snatch insects from vegetation. Around day 20–30, advances to subsurface feeding, including tipping up, and threshing vegetation for seeds. Also strains and sifts bottom substrate for food. See 160 Pietz, P. J. and D. A. Buhl. (1999). Behaviour patterns of Mallard Anas platyrhynchos pairs and broods in Minnesota and North Dakota. Wildfowl 50:101-122. Close for details. In England, plant seeds made up 95% of items in esophagus of ducklings >20 d old (271 Street, M. (1977). The food of Mallard ducklings in a wet gravel quarry and its relation to duckling survival. Wildfowl 28:113-125. Close ); in Utah, seeds made up 51% of food items for ducklings 25–30 d old and 99% of food items in ducklings >45 d old (272 Chura, N. J. (1961). Food availability and preferences of juvenile Mallards. Transactions of the North American Wildlife and Natural Resources Conference 26:121-134. Close ).

Duckling Behavior

Synchronized; one duckling starts, and others follow, in comfort movements or Dashing-and-Diving “play” (269 Pehrsson, O. (1979). Feeding behavior, feeding habitat utilization, and feeding efficiency of Mallard ducklings (Anas platyrhynchos L.) as guided by a domestic duck. Vitrevy 10:193-218. Close ). Simple comfort movements such as scratching, jaw-stretching, and nibble-preening occur within few hours of hatching; more complex movements such as high-intensity bathing first occur at about 2 wk of age (155 McKinney, F. (1965). The comfort movements of Anatidae. Behaviour 25:120–220. Close ). Ducklings respond promptly to alarm calls: rush to water's edge and freeze, flee to uplands, cluster around hen, or take cover in dense vegetation. Escape by diving if attacked.

Ducklings spend most of time feeding during daylight hours: 78% when small (Class I of 26 Gollop, J. B. and W. H. Marshall. (1954). A guide for aging duck broods in the field. St. Paul, MN: Mississippi Flyway Council, Tech. Sec. Rep. Close ), 65% in Class II stage, and 57% in Class III stage (270 Ringelman, J. K. and L. D. Flake. (1980). Diurnal visibility and activity of Blue-winged Teal and Mallard broods. Journal of Wildlife Management 44:822-829. Close ; see also 160 Pietz, P. J. and D. A. Buhl. (1999). Behaviour patterns of Mallard Anas platyrhynchos pairs and broods in Minnesota and North Dakota. Wildfowl 50:101-122. Close ). Older ducklings tend to spend more time in comfort and resting activities than younger ducklings (270 Ringelman, J. K. and L. D. Flake. (1980). Diurnal visibility and activity of Blue-winged Teal and Mallard broods. Journal of Wildlife Management 44:822-829. Close , 160 Pietz, P. J. and D. A. Buhl. (1999). Behaviour patterns of Mallard Anas platyrhynchos pairs and broods in Minnesota and North Dakota. Wildfowl 50:101-122. Close ).

Only hen cares for ducklings. Ducklings feed themselves without assistance. Hen leads brood from nest to water and to abundant food. Broods ducklings until about 2 wk old (262 Caldwell, P. J. (1973). Development of thermoregulation in Mallard ducklings. Condor 75:113-114. Close , 190 Rhymer, J. M. (1988). The effect of egg size variability on thermoregulation of Mallard (Anas platyrhynchos) offspring and its implications for survival. Oecologia 75:20-24. Close ). Protects brood by calling to regroup strays, gives alarm calls to warn of danger, or uses broken-wing displays to distract predators away. Hen leaves brood for recesses; average absence >27 min (range 2–>80 min) in Minnesota (160 Pietz, P. J. and D. A. Buhl. (1999). Behaviour patterns of Mallard Anas platyrhynchos pairs and broods in Minnesota and North Dakota. Wildfowl 50:101-122. Close ). Hen may leave older broods for recess during day and return to accompany them at night (273 Ball, I. J., D. S. Gilmer, L. M. Cowardin and J. H. Riechmann. (1975). Survival of Wood Duck and Mallard broods in north-central Minnesota. Journal of Wildlife Management 39:776-780. Close ).

Close proximity of broods and molting drakes in crowded populations leads to aberrant parental behavior (193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close , 86 Figley, W. K. and L. W. VanDruff. (1982). Ecology of urban Mallards. Wildlife Monographs 81:1-39. Close ). Hens occasionally care for their broods jointly. Drakes often assault hens with newly hatched broods, sometimes fatally. Ducklings may scatter during this harassment, resulting in many strays. At other times, ducklings become confused among all the broods and imprint on another female. Some hens attack stray ducklings, but others accept them.

Length Of Care

Hen usually stays with brood until ducklings can fly. In n. Minnesota, hen stayed with brood average of 50 d; early abandonment associated with increased duckling mortality; hens remained for 1–2 wk after fledging, and several flightless molting hens associated with their fledged ducklings (273 Ball, I. J., D. S. Gilmer, L. M. Cowardin and J. H. Riechmann. (1975). Survival of Wood Duck and Mallard broods in north-central Minnesota. Journal of Wildlife Management 39:776-780. Close ). In N. Dakota, 86% of prefledged broods surveyed in late Sep 1993 still accompanied by hens that had not yet molted, despite lateness of season (G. Krapu unpubl.).

Nest Sanitation

Brood rarely returns to nest, so nest requires no maintenance after hatching. Hen does not remove hatched eggshells, but may remove shells broken during incubation.

Does not occur in this species.

Identity Of Parasitic Species

Mallard nests occasionally parasitized by Redheads, Ruddy Ducks, Lesser Scaup (Aythya affinis), Gadwalls, Northern Shovelers (Anas clypeata), Northern Pintails, Cinnamon Teal, Common Goldeneyes (Bucephala clangula), and, in crowded conditions, other Mallards (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close ; Titman and Lowther 274 Titman, R. D. and J. K. Lowther. (1971). Parasitism of Mallard nests by Common Goldeneyes. Canadian Field-Naturalist 85:323-324. Close , 193 Titman, R. D. and J. K. Lowther. (1975). The breeding behavior of a crowded population of Mallards. Canadian Journal of Zoology 53:1270-1283. Close ; 275 Talent, L. G., G. L. Krapu and R. L. Jarvis. (1981). Effects of Redhead nest parasitism on Mallards. Wilson Bulletin 93:562-563. Close ; 276 Lokemoen, J. T. (1991). Brood parasitism among waterfowl nesting on islands and peninsulas in North Dakota. Condor 93:340-345. Close ).

Frequency Of Occurrence; Season Or Geographic Variation

Rate of parasitism highly variable; depends on habitat conditions and nesting density of host and parasite. High water levels, reduced nesting cover, and high nest densities lead to higher parasitism rates. Mallards nesting close to water more frequently parasitized by Redheads than those nesting farther upland (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close , 277 Giroux, J. F. (1981d). Interspecific nest parasitism by Redheads on islands in southeastern Alberta. Canadian Journal of Zoology 59:2053-2057. Close ). Mallard nests initiated later in the season more frequently parasitized than earlier nests (276 Lokemoen, J. T. (1991). Brood parasitism among waterfowl nesting on islands and peninsulas in North Dakota. Condor 93:340-345. Close ). Reported frequencies of parasitism include 50% of marsh nests in N. Dakota (n = 24; 275 Talent, L. G., G. L. Krapu and R. L. Jarvis. (1981). Effects of Redhead nest parasitism on Mallards. Wilson Bulletin 93:562-563. Close ), 8.2% in central N. Dakota (n = 49; 276 Lokemoen, J. T. (1991). Brood parasitism among waterfowl nesting on islands and peninsulas in North Dakota. Condor 93:340-345. Close ), 28% of wetland nests in Utah (n = 29; 278 Joyner, D. E. (1976). Effects of interspecific nest parasitism by Redheads and Ruddy Ducks. Journal of Wildlife Management 40:33-38. Close ), and 31.5% in Alberta (n = 132; 277 Giroux, J. F. (1981d). Interspecific nest parasitism by Redheads on islands in southeastern Alberta. Canadian Journal of Zoology 59:2053-2057. Close ).

Host Response

Redhead and many dabbling duck eggs similar in appearance to Mallard eggs and readily accepted; only most conspicuous eggs rejected (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close ). Occasionally, Mallard hen will attempt to defend against parasite hen. If parasitism occurs early in laying cycle, host hen may abandon nest. Broodiness of hen increases as nesting cycle progresses, and nest desertion decreases. In N. Dakota, no significant difference in abandonment of parasitized versus nonparasitized nests (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close , 275 Talent, L. G., G. L. Krapu and R. L. Jarvis. (1981). Effects of Redhead nest parasitism on Mallards. Wilson Bulletin 93:562-563. Close ). Mallard hen and ducklings show no differences in behavior toward parasite ducklings in brood (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close ).

Effects Of Parasitism On Host

Interspecific parasitism lowered Mallard clutch size at 2 N. Dakota sites from 7.2–9.6 to 5.6–6.0 eggs in parasitized nests (275 Talent, L. G., G. L. Krapu and R. L. Jarvis. (1981). Effects of Redhead nest parasitism on Mallards. Wilson Bulletin 93:562-563. Close , 276 Lokemoen, J. T. (1991). Brood parasitism among waterfowl nesting on islands and peninsulas in North Dakota. Condor 93:340-345. Close ). In Utah, however, average clutch sizes of unparasitized (7.2; n = 18) and parasitized (6.8; n = 11) nests did not differ (278 Joyner, D. E. (1976). Effects of interspecific nest parasitism by Redheads and Ruddy Ducks. Journal of Wildlife Management 40:33-38. Close ). Mallard eggs displaced by the parasite (35% of Mallard eggs displaced; 275 Talent, L. G., G. L. Krapu and R. L. Jarvis. (1981). Effects of Redhead nest parasitism on Mallards. Wilson Bulletin 93:562-563. Close ). Eggs also may be lost if hen accidentally pushes them out while defending nest, or by addition of too many eggs for nest to hold. Nevertheless, Weller (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close ) concluded that effect of interspecific parasitism on Mallard populations was not significant because Mallard nest or hatch success not affected by parasitism and parasitism rates too low relative to number of Mallards.

Success Of Parasite With This Host

In Manitoba, most Redhead eggs laid after Mallard incubation already started. As a result, 91% of Redhead eggs in Mallard nests failed to hatch (258 Weller, M. W. (1959b). Parasitic egg laying in Redhead (Aythya americana) and other North American Anatidae. Ecological Monographs 29:333-365. Close ). In N. Dakota, Redheads parasitized many Mallard nests before incubation began; parasitized nests contained an average of 3.8 Redhead eggs, which produced an average of 1.5 Redhead ducklings (275 Talent, L. G., G. L. Krapu and R. L. Jarvis. (1981). Effects of Redhead nest parasitism on Mallards. Wilson Bulletin 93:562-563. Close ).

See Young birds, above.

Young ducks able to fly and independent at approximately 52–70 d. Initial flights occur within natal marsh; young birds in Minnesota began to go on forays out of the natal marsh about 3 wk after able to fly (279 Kirby, R. E., L. M. Cowardin and J. R. Tester. (1989). Premigrational movements and behavior of young Mallards and wood ducks in north-central Minnesota. U.S. Fish Wildl. Serv., Fish Wildl. Res. 5. Close ). Learn local area by accompanying other birds; may stay in natal area throughout autumn until migration. Flying juveniles join adult flocks in autumn to migrate; subordinate to adults their first winter.