Food Habits

Main Foods Taken

Benthic invertebrates in fresh and salt water—e.g., fly (Diptera) larvae, polychaete worms, amphipods, isopods, decapods, bivalves and gastropods, copepods, and larvae of long-legged flies (Dolichopodidae) and beach flies (Canacidae; Smith 1998). Species and families taken in Suriname: Anachus sp., Melampus coffeus, Odostomia leavigata, and Turbonilla sp. (snails [Gastropoda]); Ochtebius sp. (beetles [Coleoptera]); larvae of soldier flies (Stratiomyidae) and shore flies (Ephydridae; Haverschmidt and Mees 1994). Terrestrial invertebrates commonly eaten are flies, beetles, and spiders (Araneida; Skagen and Oman 1996, Smith 1998).

Microhabitat For Foraging

Requires open, even substrate for running—wet or damp, never dry (Recher 1966, Burger et al. 1979, Smith 1998). On breeding grounds in Churchill, Manitoba, feeds at edges of lakes, ponds, and rivers, dried- or drying-up lagoons left by snow runoff (MSB), and tidal mudflats around large blocks of melting ice (EN). In Venezuela, feeds mainly at intermediate and low tide levels (Robert et al. 1989); in Panama Canal Zone, at low tide over entire feeding area (Strauch and Abele 1979). In Churchill, Manitoba, adults and chicks feed at high-tide zone during all tidal levels; along lakes and ponds, feeds over entire area but only up to tarsal level in water (MSB). During migration in Virginia, forages in freshly plowed or sparsely vegetated agricultural fields when tidal flats are covered by high tide (Rottenborn 1996), impoundments where water is <3 cm, and damp mudflats with little or no vegetation (Wilds 1990). In Saskatchewan, forages on muddy sand, mostly on dry or saturated substrate without standing water (Alexander and Gratto-Trevor 1997). No sexual or age differences described in habitat selection during foraging (Smith 1998), but small sample sizes for ages. While foraging, distance to water line not significantly different for males and females; averages 4 m (Smith 1998).

Food Capture And Consumption

Searches for prey visually. Runs several steps, stops, stares, and then pecks or quickly snatches at prey. Catches prey by tipping forward at ankle, tail raised as head goes down (Strauch and Abele 1979). Baker and Baker (1973) reported extreme stereotypic behavior and habitat use in Churchill (Manitoba) and Florida (between seasons). In Venezuela, however, foraging bouts less commonly (30–40%) using repetitive hammering of bill into substrate, up to depth equal to length of bill (Smith 1998). On outer coast of Washington, feeds on “thin worms” (probably polychaetes or nemerteans, up to 10 cm long, 1 mm diameter) on sand beaches, pulling them slowly out of sand, having to stretch up to maximum height to do so (D. Paulson pers. comm.). Neither feeding rate nor locomotion rate is related to air temperature, number of conspecifics, or total number of shorebirds within 7–8 m (Baker and Baker 1973). Makes 0.24 foraging attempt/s winter and summer (n = 972 winter, n = 523 summer; Baker and Baker 1973). Foraging attempts/30 cm of locomotion: 0.85 in winter, 0.65 in summer (Baker and Baker 1973). Little change in niche breadth over season (Baker and Baker 1973). Locomotion rate while foraging: 0.81 cm/s winter, 1.1 m/s summer (Baker and Baker 1973). In Venezuela (a migratory stopover and wintering area), forages at night, more likely on fully or partially moonlit nights than on moonless ones, although tidal changes help explain the diurnal and nocturnal abundance of birds (Robert et al. 1989, Robert and McNeil 1989). Large eyes probably help make visual feeding possible at night (Robert et al. 1989). In California, presence of foraging birds during day and at night increased during fall, but not during spring (Dodd and Colwell 1998). From Oct to Apr in ne. Venezuela, feeds during most of daylight hours, less so in Jan and Feb (Morrier and McNeil 1991). Forages most actively between dawn and 10:30 (A. C. Smith pers. comm.). When prey occur in thin film of mud on surface of substrate, Foot-Quivering (also called “foot-stir” or “foot-tremble”; foot, extended forward at about 45°, trembles slightly on substrate) is observed on breeding and migration grounds; similar to that seen in Common Ringed Plover (Osborne 1982). Probably functions to cause prey to move, making them more conspicuous (Osborne 1982). No relationship between feeding methods and wind velocity or moon phases (Robert and McNeil 1989). Peck and probe rates in Venezuela range from 16 to 17/min; not different between sexes (Smith 1998). Spends 35–90% of each day foraging during winter in Venezuela, consistently more than Wilson’s Plovers do at same site (Morrier and McNeil 1991; see Behavior: self-maintenance, below). Handling times for polychaetes are very fast (<1 s); times for other prey not documented. Capture success not known.

Stomach contents of 3 Semipalmated Plovers collected during Jun at coastal sites in Churchill, Manitoba: 41.6% by weight fly larvae, 56.4% grit, 2% unknown. One bird captured inland had mainly vegetation and stones and 1 spider in its stomach (MSB). Similarly in Churchill, Baker (1977) reported 65% fly larvae, 8% plant seeds, 15% spiders in 33 stomachs. In Panama in winter, 82% of prey items (n = 408 prey items from 13 stomachs) were polychaete worms; individuals took smaller food items (mean 1.81 mm, n = 408) and were more specialized than other species sharing the feeding site (Strauch and Abele 1979). At Palo Alto, CA, 3 stomachs con-tained 2.8% Gemma gemma (a pelecypodid), 94.5% Neanthes succinea (a polychaete), 2.2% Ilyanassa obsoleta (a snail), 0.5% ostracod species (Recher 1966). In Bay of Fundy, a stopover site during southern migration, Corophium volutator (an amphipod) made up 47.6% of diet; remainder was polychaetes Nereis sp. and Glycera sp., bivalve Macoma balthica, and gastropod Hydrobia totteni (Napolitano et al. 1992). In St. Lawrence Estuary, on southern migration, mainly polychaete Nereis virens averaging 2.4 mm ± 0.049 SE in size (n = 362); present in all stomachs (n = 30).

In New Jersey, 2 stomachs from individuals collected during spring migration: 77% polychaetes, 18% detritus, 3% horseshoe crab eggs, 2% sand (N. Tsipoura pers. comm). Average prey size for 3 stomach samples from central coastal California about 5 mm (n = 137 prey items; Recher 1966). Fly larvae found in feces from Venezuela were about 10 mm, larvae of long-legged flies 0.58 mm ± 0.015 SE (n = 108), larvae of beach flies 0.053 mm ± 0.001 SE (n = 60), bivalve mollusks 0.52 mm ± 0.022 SE (n = 45), copepod crustaceans 0.41 mm ± 0.016 SE (n = 111). No difference in size of prey items between males and females in Venezuela, but difference in composition: males (n = 19 fecal samples)—31% copepod crustaceans, 54% long-legged fly larvae, 14% bivalve mollusks, 1% beach fly larvae; females (n = 20 fecal samples)—37% copepod crustaceans, 37% long-legged fly larvae, 25% bivalve mollusks, 1% beach fly larvae (G = 15.49, p < 0.0001); similar differences at second site (Smith 1998). Fewer prey items found in male feces than in female feces, per-haps because copepods and bivalves of females are smaller than fly larvae consumed by males (Smith 1998).

Semipalmated Plovers have small but powerful bills, most suitable for snatching prey from surface, but also exhibit some hammering to depth of bill. Chooses wide selection of surface prey species and sizes depending on location; can be either highly selective or opportunistic, depending on location (Baker 1977, Strauch and Abele 1979, Michaud and Ferron 1990, Skagen and Oman 1996).

No data on nutrition. See Skagen and Oman 1996 for Semipalmated Sandpipers, which over-lap in diet with Semipalmated Plovers in parts of northern range. For average caloric content of most common prey, see Gratto-Trevor 1992 .

Basal metabolic rate was determined for adult breeding Semipalmated Plovers placed in a metabolic chamber for 12 h and monitored over a range of temperatures (–10° to 30°C); minimum O₂ consumption occurred at 20°C (n = 6; M. Williamson pers. comm.). Basal metabolic rate >25%, greater than predicted by general equation relating body mass to basal metabolic rate (M. Williamson pers. comm.), but similar to that found in Little Ringed Plover (Kendeigh et al. 1977, Kersten and Piersma 1987).

In Venezuela, most fecal pellets contain identifiable prey, including insect mandibles, legs, and setae (polychaetes; Smith 1998). Drinking commonly observed on breeding grounds (EN) and during migration. Relative salt gland mass is 0.07 (g/g body mass) for congeneric Common Ringed Plover (Rubega and Robinson 1997).