Diet and Foraging
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Main Foods Taken
Grain (rice, wheat, corn, barley), moist-soil and aquatic plant seeds, pond weeds, aquatic insects, crustaceans, worms, and snails.
Microhabitat For Foraging
Nesting adults and ducklings feed in shallow, temporary to semipermanent wetlands. In fall and winter, species forages in dry or shallowly-flooded harvested rice, grains and other crop fields; fresh, brackish, and marine wetlands of several types; and bays, reservoirs, and salt ponds. During spring migration, feeds in shallow snowmelt and rain-puddled ponds in pastures, grasslands, grain fields, and native wetlands.
Food Capture And Consumption
Forages singly or with mate in nesting season, and in flocks in nonbreeding and early nesting seasons. Feeds while walking in dry fields, in very shallow water, or at water's edge by picking up food items from ground and water or from standing seed heads. Dabbles for food items at water surface by filter feeding with bill; tips up in shallow wetlands and sometimes dives to reach bottom seeds (Miller 1983d).
In fall and winter, daily foraging pattern varies with available habitats and disturbance levels and thus differs regionally and seasonally. Will use the same wetland or flooded field for both foraging and roosting if undisturbed and food density is adequate (Fleskes et al. 2002), but during most of winter makes one or two trips each day between roost and feeding habitat. Where productive wetland or flooded crop (esp. rice and other grain) fields are available for foraging, feeds primarily in morning and evening in dry fields, and at night in flooded fields and wetlands. Often makes evening and morning feeding flights from day roosts to forage in dry harvested grain fields (Bossenmaier and Marshall 1958, Baldassarre and Bolen 1984), or 1 flight around dusk after sunset, remains all night, and returns to roost habitat around dawn or when disturbed (Miller 1985b, Cox and Afton 1996, Fleskes et al. 2003, 2005a,b; R. R. Cox pers. comm., MRM, JPF).
Evening flights average 6.8 km (some >25 km) in the Sacramento Valley, CA (MRM) and 14.4 km (1–50 km) in Louisiana (R. R. Cox pers. comm.). When foraging primarily in dry crop fields, makes 2 round-trip flights, once in morning and once in evening (Baldassarre and Bolen 1984, Moon 2004). One-way flight distances between roost and feeding sites have been reported as high as 43 km (Fleskes et al. 2003) to 50 km (R. R. Cox pers. comm.) and averaged 3.3 to 7.0 km in California (Fleskes et al. 2005b), 8.7 to 24.4 km in Louisiana (Cox and Afton 1996), and 3.7 to 12.24 km in Texas (Moon 2004). Foraging flocks can damage grain crops in Canada and U.S. (Knittle and Porter 1988).
Major Food Items And Quantitative Analysis
Nesting adults. Animal foods are particularly important to hens in prairie regions during prelaying and laying periods (56 and 77% aggregate percent volume, respectively): Diptera larvae (especially Chironomidae [midges]), snails (Gastropoda), Crustacea, earthworms (Oligochaeta) (Krapu 1974b, Krapu 1974c). Animal foods are less important to birds nesting in Alaska; interior Alaska: 29% invertebrates (especially midge larvae, snails, clams [Pelecypoda]; Burris 1991); nw. Alaska: 29% invertebrates (caddis fly larvae [Trichoptera], Diptera larvae [especially Tipulidae], snails, water boatmen; Debruyckere 1988). Important vegetable foods in N. Dakota include cereal grains and barnyard grass (Echinochloa crusgalli) seeds; in Alaska tubers, seeds of Callitrichaceae, sedge, crowberry (Empetrum), Potamogeton, and Hippuris.
Ducklings. Predominantly insect larvae, especially midges; also snails and Crustacea (especially Cladocera) during first few days of life in prairies and other interior habitats (Sugden 1973a). Important plant foods include grass (Gramineae) and bulrush (Cyperaceae) seeds. During first 40–50 d, invertebrates comprise about 67% of diet in central Alberta (Sugden 1973a), >80% in N. Dakota (predominantly snails and midge larvae; Krapu and Swanson 1977), and 31–46% in nw. Alaska (mayfly [Ephemeroptera], midge, and caddis-fly larvae; clams; and water boatmen; Debruyckere 1988). Mosquito (Diptera: Culicidae) and damselfly (Odonata: Enallagma) also recorded in Alaska.
Postbreeding birds. Flightless adults at Pel Lake, Saskatchewan, consume 33% (by volume) alkali bulrush (Scirpus paludosus), 15% sago pondweed (Potamogeton pectinatus), and 43% unidentified organic material and invertebrates (Keith and Stanislawski 1960). Flightless, postbreeding males in marshes adjacent to Great Salt Lake, UT, consume 34% animal matter (>90% Corixids), 50% bulrush seeds, and 15% wigeongrass seeds (Cox 1993).
Fall migration. In se. Alaska, 72% of diet is vegetable matter, especially sedge achenes (58% of total dry weight); clams most important animal food (20% of total dry weight) (Hughes and Young 1982). In Utah's Bear River marshes, diet is 100% plant matter, including sago pondweed (27% total volume), bulrush (20%), horned pondweed (Zannichelia palustris) (6%), and wigeongrass (4%) (Fuller 1953). In ne. California, red goosefoot seeds (Chenopodium botryodes; 12–52% aggregate percent volume), alkali bulrush seeds (≤27% aggregate percent volume), and invertebrates, (18–81% aggregate percent volume, especially midges), are important in fall (Pederson and Pederson 1983).
Winter. Predominantly seeds and vegetative material but also aquatic invertebrates and earthworms. In California, rice supports more pintails than any other single food item (Fleskes et al. 2005) but outside the Sacramento Valley region rice is mostly unavailable. In the Sacramento Valley, CA, consumes ≥97% plant food from wetland and rice habitats but invertebrates increase to 29–66% (aggregate percent dry weight) in Feb–Mar (Miller 1987b).
Important seeds other than rice include swamp timothy (Heleochloa schenoides), barnyard grass, flatsedges, southern naiad (Najas guadalupensis), and smartweeds (Polygonum spp.) and; important invertebrates include midges, snails, and beetles (Coleoptera). In Suisun Marsh, CA, mostly marsh and grass seeds, especially sea purslane (Sesuvivum verrucosum) (Miller et al. 2009). Marsh and grass seeds (esp. smartweeds) also comprise most of the diet in the Sacramento-San Joaquin Delta, CA, but corn, tomato and other crop seeds are also important (Miller el al. 2009). Mostly marsh seeds (esp. swamp timothy and barnyard grass) in the San Joaquin Valley, CA, but aquatic invertebrates (esp. midge larvae) are an important part (Euliss and Harris 1987) or majority (Connelly and Chesemore 1980) of the diet earlier in winter (e.g., Nov) than in the Sacramento Valley. Midge larvae, earthworms, and grain important in flooded fields in the s. San Joaquin Valley (JPF). On Mexico's west coast (Sinaloa), these ducks consume ≥90% (aggregate percent volume) plant material, primarily alkali bulrush (Migoya and Baldassarre 1993); in the Yucatán, >99% (aggregate percent volume) tubercles of muskgrass (Chara; Thompson et al. 1992c).
Along the Texas Gulf Coast, submersed vegetation of shoalgrass (Diplanthera wrightii) rhizomes (mostly) and foliage dominates diets (≤88% volume; Mcmahan 1969; 11% – 62% aggregate percent dry mass; Ballard et al. 2004) and wigeongrass (Ruppia maritima) seeds (<1% – 46%), along with amphiphods (Gammarus spp.), and dwarf surf clams (Mulinia lateralis; >71% (aggregate dry mass; Ballard et al. 2004). In the Playa Lakes region of the Texas Panhandle, hunter-shot birds contained >90% corn and 5% animal matter, whereas those collected while feeding in playa wetlands contained 27% corn, 50% non-agricultural seeds (e.g., barnyard grass, smartweeds, dock [Rumex spp.]), and 21% animal matter, primarily beetle larvae (Sheeley and Smith 1989).
In brackish impoundments in S. Carolina, diet >99% plant matter, particularly muskgrass, wigeongrass, alkali bulrush, sea purslane (Sesuvium maritimum), tall red-top (Tridens flava), sea blite (Suaeda depressa), and spike rush (Eleocharis parvula) (Kerwin and Webb 1971, Prevost et al. 1978, Swiderek et al. 1988).
Spring Migration. Primarily marsh and agricultural seeds but invertebrates increase in diet as they become more available. In s.-central Nebraska, 98% (aggregate dry mass) of the diet was seeds (Pearse et al. 2011). Pintails returning to roost after evening forage trips had consumed 84% (aggregate dry mass) corn, 5% Polygonum, and 4% Echinochloa seeds; pintails collected feeding in the marsh had consumed 54% corn, 23% Polygonum, and 12% Echinochloa seeds; Chironomidae was the main invertebrate in the diet. In SONEC, diet on flooded pastures and hay fields was 89% (aggregate dry mass) seeds including 34% Reed Canary (Phalaris arundinacea), 23% Spike Rush (Eleocharis sp.), 5% Fat Hen (Atriplex prostrate), and 4% Stalked Popcorn Flower (Plagiobothrys stipitatus); remainder of the diet was comprised of vegetation (7%), earthworms (2%), snail shells (<2%), and insects (1%, mostly Chironomidae) (JPF). Diet in marshes was also mostly seeds during early spring with red goosefoot, alkali bulrush, and foxtail barley (Hordeum jubatum) prevalent; consumption of invertebrates (esp. Chironomidae) increased as spring progressed with invertebrates comprising 40-95% (aggregate volume) in some marsh types (Pederson and Pederson 1983).
Food Selection and Storage
Generally selects feeding habitats that provide abundant food, consuming the most abundant items in proportion to their availability (Euliss and Harris 1987, Miller 1987b, Debruyckere 1988, Thompson et al. 1992c). In the Sacramento Valley, CA, birds consume seeds of rice, swamp timothy, and barnyard grass in proportion to their availability in fall but in disproportionately higher amounts in midwinter (Miller 1987b); smartweeds are under-represented in the diet until midwinter, southern naiad and flatsedges are consumed in disproportionately high amounts, and invertebrates are consistently preferred or taken proportionate to their availability in Feb and Mar. In spring in the Klamath Basin, CA, among foods consumed in large amounts, preference was for alkali bulrush seeds and midge larvae (Pederson and Pederson 1983). On the prairies, nesting females select macro-invertebrates in wetlands, although abundant seeds and agricultural grains are available (Krapu 1974c), but in Alaska, macro-invertebrates, a smaller proportion of diet, are taken in proportion to abundance (Debruyckere 1988).
Body lipid reserves vary seasonally in winter (Miller 1986c, Smith and Sheeley 1993a) and differ among regions. Body masses of pintails on the upper Gulf Coast of Texas during 1986-2000 (Haukos et al. 2001) were 1.7% lower than those wintering in the Playa Lakes Region (Smith et al 1992) but 8.4% greater than pintails in Mexico (Migoya and Baldassarre 1995). In dry winters in Texas (and also in California before recent habitat improvements), body mass and carcass fat and protein content decline, loafing and diurnal foraging increase, courtship activity decreases, and Prebasic molt in females is delayed owing to habitat/food limitations (Miller 1986c, Smith and Sheeley 1993a, Ballard et al. 2006, Moon et al. 2007).
Following increases in postharvest rice field flooding and wetland restoration in California, body mass and carcass fat gained after arrival in fall are increased or maintained throughout winter, even during dry years, especially in the Sacramento Valley (Thomas 2009, JPF). In contrast, body condition of pintails wintering in Playa Lakes Region declined 32% between 1984-1985 and 2002-2003 (Moon et al. 2007) and pintails on the lower Texas Coast leave winter 20% lighter than their fall arrival mass (Ballard et al. 2006). Lipid stores support 5- to 8-d fast in wintering Northern Pintails in Mexico (Thompson and Baldassarre 1990).
Body mass and lipids continue to increase during spring for pintails migrating through SONEC from the Central Valley of California (JPF). Yerkes et al. (2008) concluded that poor-condition, pre-breeding female pintails in Alaska had wintered and migrated near coastal areas where they exploited mainly agricultural foods, whereas good-condition females had relied more heavily on natural foods in freshwater ecosystems.
Endogenous lipid and protein reserves are important to breeding birds (Krapu 1974c, Mann and Sedinger 1993, Esler and Grand 1994b). In N. Dakota, energy and lipids for egg production of first clutches was provided by body reserves and by feeding (Krapu 1974c). In Alaska, reliance on lipid reserves is higher than in other Anas species, and carcass protein contributes 21–62% protein required for egg production in first nests (Mann and Sedinger 1993, Esler and Grand 1994b). Body lipid reserves of females generally decline through the nesting season in response to demands for egg production, maintenance, and incubation (Krapu 1974c, Mann and Sedinger 1993, Esler and Grand 1994b). Lipid and protein required for replacement clutches are obtained by feeding locally. In N. Dakota, >50% of hen's diet during prelaying and laying is macro-invertebrates, providing high protein and calcium intake for egg formation (Krapu 1974b, Krapu 1974c; Krapu and Swanson 1975). Low protein diet of grain results in lower egg production, fertility, and hatchability (Krapu and Swanson 1975).
Relative growth rate of ducklings is lower than that of most other dabbling ducks (8.9 times hatch weight at 3 wk of age; Southwick 1953). Yolk sacs contain 24% of total lipid in ducklings at hatching (Duncan 1988a); ducklings use >75% of total lipid in 4 d without food, but lean dry mass not affected, and ducklings can survive 5 d posthatch without food (Krapu 1974c).
No empirical data on basal or field metabolic rate for wild or captive Northern Pintails. Daily energy expenditure (DEE) during winter in California 146–254 kcal/d, and daily food consumption 44–74 g (MRM). In Mexico, DEE based on time-budget analysis 146.6 kcal/d (Thompson and Baldassarre 1990).
No data on temperature regulation.
Drinking, Pellet-Casting, and Defecation
No data on drinking. Seeds and vegetation move rapidly (<3.2 h) through digestive tract of captive birds (Miller 1974).