Food Habits

Main Foods Taken

In nonbreeding season, aquatic invertebrates. On breeding grounds, aquatic and terrestrial invertebrates, including annelids (Annelida), snails (Gastropoda), insects, spiders (Araneae), seeds (JRJ).

Microhabitat For Foraging

Breeding range: At Schefferville, Quebec, forages along edges of bog/fen ponds (REH). At Churchill, Manitoba, forages in wet sedge meadows (breeding birds), riverine and coastal marshes (migrants; JRJ). In meadows early in season, walks atop and around thawing sedge tussocks and probes bill deep into sides. Later, as marshes thaw, increasingly found in shallow pools, where may wade belly deep, immerse head. When guarding chicks, feeds mainly in wet sedge meadows and along vegetated edges of shallow tundra pools. Prior to migrating, flocks feed mainly in the intertidal zone (JRJ). In interior (Alberta, Saskatchewan) apparently restricted to muskegs, some with floating vegetation (Randall 1961).

During migration: inland and coastal wetlands, mud flats, and tidal flats. On bay tidal flats of mid-Atlantic Coast, frequents zone of soft mud with some standing water, covered in fall with large blades of marine algae (sea lettuce, Ulva lactuca), markedly less common in area of drier sand with some periwinkles (Littorina littorea; Burger et al. 1977). Avoids ocean beaches. In winter: tidal flats, edges of shallow pools on salt marshes, mangrove swamps.

Food Capture And Consumption

Probes into soft substrates to bill depth; may immerse head to feed in deeper water. Food captured and swallowed under substrate, except for worms, which are pulled to surface. In periods of insect abundance and when guarding chicks, will glean insect from land, vegetation.

Feeds by rapid, vertical probing in soft mud, water. Most commonly probes around itself with pivoting movements of the body, then makes a step or 2 and repeats process. Feeds in water up to belly depth, sometimes while swimming. Forages by day and night, relying on touch (McNeil and Robert 1986) and possibly taste clues. Night activity enhanced by high density of rods in retina (Rojas de Azuaje et al. 1993).

Dowitchers “typically forage in cohesive flocks of non-agonistic individuals that move as groups across the flats” (Mallory and Schneider 1979: 271), using probe-multiple-halting and probe-single-halting foraging methods. “Individual birds turned frequently, often returning to certain spots to forage rapidly” (Mallory and Schneider 1979: 272).

Burton (1972) distinguished 2 feeding movements: jabs, brief movements in which bill is thrust into the mud and immediately withdrawn, and probes, more prolonged movements often accompanied by rapid, up-and-down quivering action. Probes generally deeper, mostly between one-third and full length of the bill, and last longer (mean 1.7 s, maximum 7.3 s). Jabs are shallower, to less than half of bill length, and usually last <0.5 s. Baker and Baker (1973) found that multiple probing motion, using either steady or halting movements, were characteristic on breeding and wintering grounds; single probes significantly less frequent.

Major Food Items

On breeding grounds, mainly larvae and pupae of Diptera, also snails, beetles (Coleoptera) and other insects; sometimes plant material, particularly seeds. Short-billed Dowitchers collected at Churchill in sedge meadows in Jun and Jul had fed on spiders, small freshwater snails, midges (Chironomidae), mosquitoes (Culicidae), and other freshwater invertebrates (JRJ). Foods taken in intertidal zone unknown.

Quantitative Analysis

In migrants (n = 191) mainly on Atlantic Coast, diet 88% animal, 12% plant food. Animal prey comprised principally of insects (29%: mainly Diptera [flies; 18%] and Coleoptera [9%]), marine polychaetes (27%: Nephthys caeca, Scoloplos robustus), mollusks (21%), crustaceans (6%: fiddler crabs [Uca spp.], shrimps [Crago spp.]), fresh-water isopods (Cyathura carinata), and horseshoe-crab (Limulus polyphemus) eggs (3%). Plant food chiefly seeds, mainly of sedges, bayberry (Myrica spp.), pondweeds (Potamogeton spp.), wigeongrass (Ruppia maritima), and bogbean (Menyanthes spp.; Sperry 1940; see also Mallory and Schneider 1979 and Skagen and Oman 1996). On Cape Cod, MA, 2 birds feeding on intertidal flats in Aug took mainly bamboo worms (Clymenella torquata; more than half of stomach volume), amphipods, clams (e.g., gem clams [Gemma gemma]), and nereid polychaetes, whereas 2 others on sandy substrate fed mainly on amphipods (Acanthohaustorius millisi and Trichophoxus epistomus; Schneider and Harrington 1981). Fall-migrating dowitcher species in Saskatchewan feed largely on tubers of Pomatogeton pectinatus (Alexander et al. 1996).

Feeds opportunistically; exploits patchy and seasonal prey, e.g., horseshoe-crab eggs (Mallory and Schneider 1979, Castro and Myers 1993). Prey taken in mud flats on migration usually large (20–30 mm); sometimes feeds on tiny prey (e.g., Limulus eggs, 1–5 mm), if concentrated. Caching unknown. Size of prey taken at Churchill, Manitoba, documented by Baker (1977).

No information.

Basal metabolic rate for both species of dowitchers inferred at 3.4 kJ/h (Castro and Myers 1993) by extrapolation from equation for “shorebirds” (Kersten and Piersma 1987). Cloacal temperature of incubating male 40.0°C, incubating female 40.8°C. Temperature of incubation patch 38.5°C (JRJ).

Pellet-casting likely but never observed. Defecates on ground or in flight.