Food Habits

Main Foods Taken

Insects on breeding grounds. Invertebrates, primarily polychaetes (especially slender worms), bivalves, and crustaceans, on wintering grounds.

Foraging Schedule

At coast, controlled strongly by tides. Foraging rate increases fairly rapidly on falling tide, then decreases rapidly about 1 h before high tide (Baker 1974, Burger et al. 1977). At The Wash, U.K., during spring tides, leaves roosts to feed about 2–3 h after high water and returns about 2–3 h before high water, thus feeds for about 50% of tidal cycle; extended to about 80% during winter neap tides (Goss-Custard et al. 1977a). Feeds from 4.5 h before to 1 h after low tide in Mauritania (Engelmoer 1982). Feeding activity in Mauritania 95% of daytime (Engelmoer et al. 1984, Zwarts et al. 1990a), in England around 95% at neap tides but only 70% at spring tides, when high water covers feeding grounds entirely (Pienkowski 1982). No data available for freshwater or upland habitats, but latter more likely to be used at high tides.

Microhabitat For Foraging

Almost always substrate, but picks prey off low vegetation as well. Forages on open tundra in breeding season, primarily on sand or mud shores or intertidal areas during nonbreeding season. Lake shores during migration, commonly flooded fields near coast in migration and winter. Typically feeds above tide line, not following tide as many other shorebirds do (Recher 1966). In New Jersey prefers Ulva -covered soft moist mud to drier mud with less algae, wet sand with many Littorina, and dry sand with few Littorina (Burger et al. 1977). In California prefers moderately sorted fine sand to muddier, more organic substrates for feeding (Page et al. 1979). In Mauritania prefers sand to mud substrates (Engelmoer 1982). Often on rocky shores in central California (T. Hahn pers. comm.). Much more confined to marine habitats than other Pluvialis, rarely forages in dry uplands where all 3 golden-plover species common.

Little difference in prey captured on high and low sand flats at Lindisfarne, U.K., although plovers feed primarily where polychaete prey are most dense (Pienkowski 1982). Switches among available microhabitats on tidal schedule (Burger et al. 1977). In Bay of Fundy, feeds in elevated salt marshes when mud-flat invertebrate density low in spring (Hicklin 1987). Individual marked bird changed foraging patches with temperature changes to optimize rates of energy intake; consistent with strategy of resource conservation during mild conditions and use of conserved resources during cold conditions (Dugan 1982). Tends to shun areas with high densities of shorebirds, presumably because of disturbance of visually detected prey (Townshend et al. 1984).

Food Capture And Consumption

Forages primarily by sight. Forages by Stop-Run-Peck (prey seen) and Stop-Run-Stop (no prey seen, changes vantage point) mode typical of plovers. Studies on coast and in interior give means of Stop time 3–4.3 s, Run time 1.29 s, Run distance 0.66–1.3 m, and steps 1–6/s (Wishart et al. 1981, Pienkowski 1983a, Michaud and Ferron 1986, P. Shepherd pers. comm.). No studies on breeding habitat, but runs and stops as usual (DRP).

Time budget in autumn on Quebec coast: pauses about 78%, runs about 15%, prey capture and handling about 7% (Michaud and Ferron 1986). Feeding attempts 2.9/min in Manitoba (Wishart et al. 1981), 7/min on Quebec coast (Michaud and Ferron 1986), 3.1/min in Bay of Fundy (P. Shepherd pers. comm.), 7.3–15.1/min on different substrates in Mauritania (Piersma 1982), and 23.2/min in England (Burton 1974). Prey capture rate averages 0.4/min and 0.6/min at 2 sites in Bay of Fundy (P. Shepherd pers. comm.). Median intervals between prey capture in Connecticut 28 s if prey type identical and 23 s if prey type changed (Baker 1974).

General pattern of foraging varies with Stop-Run-Down-(Run)-Peck, where head held down, perhaps reconfirming prey position. Typically waits about 2.5 s before taking prey, slightly longer (3–3.5 s) before moving to new waiting site without taking prey (Pienkowski 1983a). Typically runs about 6 paces to Stop, about 4 paces to Down, and about 2 paces to Peck (Pienkowski 1983a), thus clearly moving beyond normal scanning distance in preyless run but intermediate distance when checking on previous cues. Often remains in Stop position after profitable prey (Arenicola) taken, moves farther when prey smaller (Pienkowski 1983a). Runs longer at Teesmouth, U.K., as mudflats dry out, presumably to compensate for lower frequency of Nereis (Evans 1979). Search area at each Stop estimated about 1 m²(Pienkowski 1983a). Prey probably detected by outflow of water from holes of small worms and/or casts by larger worms (Cramp and Simmons 1983).

“Thin worms” (principally Notomastus and Scoloplos) taken by 1 or more delicate upward pulls, followed by rapid flick of bird’s head as worm comes free (Pienkowski et al. 1984). Nemertean worms sometimes stretched greatly; anemones pulled loose entire from rocks or abandoned after tugging (T. Hahn pers. comm.). Worms and clams sometimes shaken vigorously in shallow water near capture site (Baker 1974, DRP), probably to remove mud. Handling times in seconds, to peck and swallow prey, on low and high flats, respectively: small items 0.65 and 0.76; thin worms 1.62 and 0.87; Arenicola  4.57 and 7.76 (Pienkowski 1983a). Handling time of thin worms rises in direct proportion to size. Handling time slightly greater for clams than polychaetes, occasionally >10 s for both (Baker 1974).

Capture success 40% (earthworms) in Manitoba (Wishart et al. 1981), 40% and 48%, respectively, in spring and fall in Connecticut (Baker 1974), 30% in Mauritania (Piersma 1982), and 91–99.4% at 2 localities in England (Pienkowski 1982). Difference perhaps because Pienkowski, by using cine camera, able to determine that many apparently unsuccessful pecks actually captured small prey. Smaller prey taken in response to scarcity of large items (Kersten and Piersma 1984), even picking up succession of small food items (Hydrobia snails) at each stop (Evans et al. 1979).

Pecking also by sidewards flick of bill, sending piece of mud flying to expose prey (Burton 1974). May insert bill completely into substrate, perhaps only into worm holes. Although considered stereotyped in foraging behavior (Baker 1974), rarely forages in water by picking prey off surface (Paulson 1990). Unlike smaller plovers, rarely uses “foot-stirring” tactic (Pienkowski 1983a). Foraging behavior basically similar to that of Greater Golden-Plover (and other golden-plovers) but less mobile and seemingly less alert, with hunched rather than upright posture; more likely to flick substrate to one side (Burton 1974, DRP).

Night feeding common, may equal daytime feeding on nights with little wind during winter. Visual feeding successful at night, pecking rate equal to daytime on moonlit night, reduced on moonless night. Adverse weather conditions, especially high winds, suppress night feeding (Pienkowski 1982). Feeds more in tidal creeks during high winds, presumably because of shelter offered (Pienkowski et al. 1984).

Major Food Items

Breeding Range. Insects, including adult and larval Diptera (Tipulidae, Chironomidae, Culicidae) and Coleoptera (Carabidae, Dytiscidae, Curculionidae), larval Lepidoptera (Tortricidae), Ephemeroptera, and Trichoptera, and more rarely, Hemiptera and Hymenoptera; also amphipods, isopods, and other freshwater crustaceans. Plant matter occasionally, including some seeds, and berries of bilberry (Vaccinium myrtillus) and crowberry (Empetrum nigrum) in late summer and autumn (Glutz von Blotzheim et al. 1975, Flint and Kondratiev 1977, Cramp and Simmons 1983). No information on food of chicks.

Nonbreeding Range. Takes relatively large prey. As in many shorebirds, specific diet varies with locality and substrate. In interior, large earthworms, grasshoppers (including Melanoplus), larval moths (Noctuidae), adult and larval beetles, seeds, and berries (Bent 1929, Payne and Howe 1976, Wishart et al. 1981). Takes fly larvae (Tabanidae and Stratiomyidae) in spring, when marine invertebrates scarce, in Bay of Fundy (Hicklin 1987). Coastal insects also eaten, including cutworms (Noctuidae) and grasshoppers (Trimerotropis) (Mackay 1892).

On n. Atlantic Coast, larger items polychaetes (Glycera, Nereis, Scoloplos), nemerteans (Cerebratulus), bivalves (Gemma, Mya, Mytilus), snails (Hydrobia, Turbonilla), amphipods (Corophium), and shrimp (Crangon) (Baker 1974, Hicklin and Smith 1979, Schneider and Harrington 1981, Michaud and Ferron 1986, P. Shepherd pers. comm.). In Pacific Northwest, takes many thin polychaetes and lugworms (Abarenicola; DRP). On central California coast, takes small (1 cm) sea anemones (Anthopleura elegantissima) when feeding on rocks (T. Hahn pers. comm.). Only tropical American information from Panama, where crabs, beetles, polychaetes, sea urchins, and fish eaten (Schneider 1985). Carrion (dead crab [Bent 1929]) occasional in diet.

Much information from Old World (Pienkowski 1982, Piersma 1982, Durell and Kelly 1990, Kalejta 1993, Turpie and Hockey 1993). Breadth of diet greater than that of Greater Golden-Plover feeding at shore and largest prey items somewhat larger (Burton 1974) (other Pluvialis not studied).

Quantitative Analysis

Breeding Range. One bird from Perry River region, NWT, contained flies, including 50 larval tipulids and 15 adult dolichopodids (Hanson et al. 1956). A sample of 23 stomachs from Wrangel I. included 170 caterpillars (up to 60 in one stomach), 152 adult beetles (107 chrysomelids), 120 caddisfly larvae, 40 amphipods and other crustaceans, 34 flies, remains of unidentified insects, and in 2 stomachs, grass remains and seeds. Some stomachs also contained coarse sand and gravel, the latter up to 8–10 mm in diameter (Glutz von Blotzheim et al. 1975).

Nonbreeding Range. Bloodworms (Glycera dibranchiata) make up 55% of diet by volume in Bay of Fundy (P. Shepherd pers. comm.). Three California stomachs included 67.3% gastropods (Ilyanassa obsoleta), 16.4% polychaetes (Nereis succinea), and 16.3% bivalves (Gemma gemma, Mya arenaria, and Macoma inconspicua) (Recher 1966).

In coastal U.K., thin worms definitely identified in 70–80% of prey captures in Northumberland. Macoma remains found in 90% and Cerastoderma in 47% of 60 pellets examined at The Wash; Lanice polychaetes may have been most abundant prey but not represented in pellets (Goss-Custard et al. 1977b). Arenicola rare but important in diet at Lindisfarne; average size  Arenicola 973 cal, versus modal size thin worms 15 cal. Arenicola contributed 64 and 83% of total energy intake, thin worms 29 and 10%, and crabs 5 and 5% on low flats and high flats, respectively (Pienkowski 1982).

Prey selection presumably based on foraging behavior, with invertebrates detected visually (some evidence of their presence at surface) playing largest part in diet. Within this broad constraint, probably a generalist. Apparently selects large prey by not responding to cues of small prey at start of each waiting period (Pienkowski 1981, 1983a). Also more likely to select large prey when environmental conditions optimal (Pienkowski 1981). Within waiting period, readiness to accept small items increases. Size selection of prey apparent in quantitative studies, although not compared with frequency distribution of prey available. Of 1,023 thin worms captured, 80% were one-half x bill height, with a stretched length of ≤6 cm; largest worms captured were 2 x bill height, with stretched length of 24 cm. Of 62 Arenicola captured, 76% in 6–12 cm range, 18% smaller, and 6% larger (Pienkowski 1982). Selected nereids averaging larger (1.5–7 cm) than range present in substrate (0.5–6 cm) in South Africa, essentially ignoring those <2 cm (Kalejta 1993). Occasionally clams extracted that are too large, then abandoned (Baker 1974).

Daily food consumption 16–22 g, decreasing linearly from 2 to 16°C (Kersten and Piersma 1987). Basal metabolic requirements (BMR) estimated as 25–29 Kcal/d, minimum energy requirements 87 Kcal/d, approximately 3–3.5 x BMR (Evans et al. 1979). Estimates of energy intake of 0.53–2.68 x BMR during daytime low-water period thus show diurnal nutrition inadequate to meet energy requirements, and some individual birds obtain more energy from nocturnal than diurnal feeding, perhaps because large prey (Nereis) are much more surface-active at night (Dugan 1981). Nocturnal feeding, for which species well adapted (Rojas de Azuaje et al. 1993), essential to winter survival at high latitude.

On tropical wintering grounds in Mauritania, amount of time spent feeding increased by adding moonlit night feeding and then fully dark night feeding as time of migration approached, presumably to raise energy intake (Zwarts et al. 1990a). Also feeds at night in early spring in Panama (Schneider 1985). However, plovers do not have to feed at night to meet minimum energy requirements in spring and fall on Wadden Sea, Netherlands, and are able to deposit fat for migration in spring, probably because of >1 low tide during daylight (Kersten and Piersma 1984).

Because of visual feeding style, foraging success and thus energy acquisition much reduced during adverse weather; thus plovers more successful in tropics (Pienkowski 1982).

Daily energy expenditure high in this and other shorebirds, probably related to premigratory fattening and survival during severe winter weather (Kersten and Piersma 1987). Plovers typically build up larger fat reserves (lipid index 22%) than sandpipers in autumn at high latitudes (Davidson 1981, Pienkowski et al. 1984), perhaps to counter problem of winter stress. Pectoral muscles 7–8% of total lean body weight (comparable to other plovers but greater than sandpipers), probably partially metabolized along with lipids during extreme nutritional stress. As much as 35% of lean weight lost during extreme winter conditions by birds that survive (Davidson 1981). At lower latitudes, no weight gain during winter, presumably not necessary to compensate for harsh weather conditions.

BMR 50% greater than predicted by general equation. Temperature coefficients of metabolic rate high in this and other shorebirds, indicating relatively poor insulation. Thus costs of thermoregulation high, probably explaining high BMR (Kersten and Piersma 1987).

No information on drinking. Casts pellets at some sites but not others (Goss-Custard et al. 1977a, Pienkowski 1982).