Food Habits

Main Foods Taken

During breeding season, primarily dipteran insects (adults, pupae, larvae), particularly adult and larval chironomids (midges), supplemented by spiders (Araneae), beetles (Coleoptera), Lepidoptera larvae (caterpillars), Hymenoptera (mainly bees and wasps), and certain plant material (achenes, berries) early in season (MacDonald and Parmelee 1962; Nettleship 1967, 1973; Cramp and Simmons 1983). Outside breeding season, diet extremely diverse; efficient, opportunistic feeder and scavenger. Generally crustaceans (especially amphipods, copepods, decapods, isopods, etc.), mollusks (e.g., limpets (Acmaeidae), periwinkles (Littorinidae), mussels, cockles, etc.), annelids, echinoderms, small fish, some insects (larvae and adult flies, particularly those associated with seaweed) and spiders (when available), supplemented by carrion (especially dead fish and mammals), human garbage (food and fishery discards), and birds’ eggs (see below).

Microhabitat For Foraging

Moves between breeding and wintering grounds along traditional routes, principally associated with coastal marine habitats, stopping at specific sites en route where food is predictable to replenish energy reserves (fat) in preparation for often long, nonstop flights. Many of these coastal sites have a superabundance of food when individuals are present, patterns of prey availability that are predictable on a daily, seasonal, and annual basis (see Migration: spring and fall migration, above; also Thompson 1973, Gill and Jorgenson 1979, Isleib 1979, Morrison and Harrington 1979, Pitelka 1979, Hicklin 1987, Morrison and Ross 1989, Gill and Handel 1990, Gudmundsson et al. 1991, Bradley and Bradley 1993, Castro and Myers 1993, Cadée 1994). In coastal marine areas, often forages in close flocks of 10–100+ individuals, probing, jabbing, and flipping over objects (pebbles, rocks, mollusk shells, etc.) with rapid jerks of head and bill to expose invertebrate prey. Prey pecked at or chased, most often in intertidal zone in a wide range of macro- and microhabitats, from rocky and shingly shores to exposed mudflats and reefs, and sand or gravel beaches. Activity patterns of foraging Ruddy Turnstones normally regulated by tidal oscillations (Fleischer 1983). At breeding locations, probing and jabbing techniques dominate, with foraging microhabitat highly variable according to time of season and geographic location, though always related to food availability and abundance (Nettleship 1967, 1973). On arrival in spring, exploits overwintering arthropods (various stages) located under rocks and in soil and root systems of plants, and some vegetable materials and carrion. Later, takes large quantities of insects, particularly midges and other dipterans, usually in dry to mesic tundra habitats close to fresh-water ponds and streams where the abundance and timing of insect emergence is predictable. Actively hunts spiders, beetles, lepidoptera larvae, and other terrestrial invertebrates by probing, jabbing, pecking, and chasing in wet mud or barren peat to dense vegetation, including moss and lichen (Bergman 1946, MacDonald and Parmelee 1962, Nettleship 1967, Vuolanto 1968, Nettleship 1973). After eggs hatch, adults and chicks forage in wet habitats along edges of streams, ponds, and lakes, usually in areas where recently emerged aquatic insects occur in high abundance. Family movements correspond with availability of soft-bodied, immobile, insect prey. No sexual differences between adults observed, but juvenile ability to identify prey, and rates of capture and ingestion less than adults (Nettleship 1967, 1973). Age-related differences in foraging rate and aggressive behavior best known from winter studies (e.g., Groves 1978); some individuals specialize both inside (e.g., as egg predators when nesting in association with gull and tern colonies; Crossin and Huber 1970, Brearey and Hildén 1985) and outside (Whitfield 1990) the breeding season.

Foraging Range

In breeding season, feeds on coast at arrival, mainly crustaceans and mollusks, then moves inland in small groups (usually 10–20 individuals), moving between snow-free areas for plant material and invertebrate prey, principally insect larvae, spiders, and beetles; also scavenges. Once snow begins to melt, disperses to occupy individual nest territories, which individuals defend as a breeding pair from conspecifics, and feed on for self-maintenance (chiefly invertebrates, mostly adult and larval insects and spiders) until after eggs hatch. Once chicks appear, territorial boundaries break down and family groups move by walking from area to area in relation to food availability, usually corresponding with insect emergence, especially dipteran chironomids. Later, after most adult females, many males, and all failed breeders have departed for the coast, flocks of fledglings (20–50 individuals), accompanied by a few adults (usually males), fly over tundra breeding area, feeding at sites where insect emergence occurs late. Exodus of all birds to coastal regions usually complete before reappearance of inland snow. Along coast, remaining adults and fledglings forage in flocks, largely on marine crustaceans and plant matter in preparation for initiation of fall migration. (For detailed review, see Nettleship 1967, 1973 .)

Food Capture And Consumption

Efficient and aggressive predator, using distinctive feeding methods and techniques that vary with habitat, season, and abundance of food (Nettleship 1973). Probes and digs using bill, overturns objects such as stones, mollusk shells, and seaweed with rapid jerks of head, to reveal prey, which are then quickly jabbed or pecked and eaten. Capable of moving large items and heavy mats of seaweed by head and bill movements, sometimes supplemented by vigorous body-pushing. Searches diligently for prey in cracks between rocks along shore and tide lines, even on ice-covered ponds, once insects begin to emerge. Also probes and thrusts bill in mud and sand (to depths of several centimeters) using a “probe-jab” technique (Nettleship 1973) with an upward or sideways push with the head to displace substrate and rapidly capture and consume prey (Bergman 1946; Bianki 1967; Nettleship 1967, 1973; Burton 1974; Beven and England 1977). Able to pick up individual small insect prey (dipteran insects, larvae and adults) quickly from wet ground and vegetative cover. Feeds on carrion by stripping and tearing off pieces of body tissue; also jabs and eats any blowfly or other insect larvae present on carcasses (MacDonald and Parmelee 1962, Mercer 1966, Spencer 1966, Nettleship 1967, Thompson 1973). Considerable skill in opening and eating mollusks (e.g., mussels, periwinkles, limpets), barnacles (Crustacea: Thoracica), and small crabs (Decapoda). Opens bivalves by prying apart, snails by jabbing and breaking operculum, and barnacles by striking closed bill through upper plates; tears apart small crabs and similar sized intertidal hard-bodied invertebrates (Dewar 1940, Groves 1978, Schneider 1982, Cramp and Simmons 1983). Also uses bill to break open and eat contents of eggs of other bird species when nest left unattended, particularly colonially breeding gulls and terns, but sometimes eggs of conspecifics on high-density breeding areas (Vuolanto 1968, Crossin and Huber 1970, Parkes et al. 1971, Brearey and Hildén 1985, Morris and Wiggins 1986, Whitfield 1990). In summary, an opportunist forager, with a wide diversity of techniques to locate, capture, and consume prey and food wastes.

Major Food Items

During winter and migration, primarily invertebrate prey on or near surface, particularly crustaceans, polychaetes, and mollusks. Crustaceans include barnacles (e.g., Balanus), amphipods (Amphipoda; e.g., Gammarus, Caprella), copepods (Copepoda; e.g., Calanus), and decapods (Decapoda; e.g., shrimp [Crago] and crabs [e.g., rock (Cancer), sand (Hippa, Emerita), shore (Carcinus), and hermit (Eupagurus, Pagurus)]). Polychaetes (Polychaeta; marine worms) include Nereis . Among mollusks: chitons (Am-phineura; Chaetopleura, Chiten), gastropods (Gastropoda; e.g., periwinkles [Littorina], and bivalves (Pele-cypoda; e.g., mussels [Mytilus], cockles [Cardium], and clams [Mya]). But nonbreeding diet very diverse, varying with time of year, location, and habitat; also includes Coelenterata (Anthozoa, sea anemones), Echinodermata (Asteroidea, starfish; Ophiuroidea, brittle stars; Echinoidea, sea urchins); Oligochaeta (earthworms; e.g., Lumbricus), Arachnida (Araneae [true spiders]; adults, egg cocoons), many Hexapoda (Coleoptera [beetles], Trichoptera [caddisflies], Lepid-optera [larvae], Diptera [adults, pupae, and larvae], and Hymenoptera), small fish, carrion (especially dead fish and mammals), and unattended eggs of other birds, particularly colonial Laridae (gulls) and Stern-idae (terns) (Noble 1904, Bent 1929, Bergman 1946, Stout et al. 1967, Jones 1975, Beven and England 1977, Groves 1978, Harris 1979, Loftin and Sutton 1979, McKee 1982, Cramp and Simmons 1983, Brearey and Hildén 1985, Donoghue et al. 1986, Farraway et al. 1986, Post 1988, Whitfield 1990, Cadée 1994). Also in migration, staging areas with superabundance of prey often used to build up energy reserves for lengthy nonstop movements: e.g., New England Atlantic Coast in spring, eggs of horseshoe crab on beaches at Delaware Bay (New Jersey and Delaware) in late May (Clark et al. 1993, Botton et al. 1994, Harrington and Flowers 1996); ne. Pacific in late summer (Aug), blowfly larvae at islands of the central and s. Bering Sea, including Pribilof Is. (St. George), St. Matthew, and Nunivak, and Aleutian Is. and coast of n. Alaska Peninsula (Thompson 1973, Gibson 1981, Gill and Handel 1981, Gill et al. 1981, Kessel 1989); also Commander Is. in past (Stegneger 1885, Bent 1929).

On high-arctic North American breeding grounds (Lake Hazen, Ellesmere I., Queen Elizabeth Is.) nest close to wet areas that remain moist to late summer providing local food supply, principally dipteran insects (especially chironomid adults and larvae), which form most of the summer diet for adults and young. At arrival in late May along coast, mainly crustaceans (amphipods, Gammadidae; barnacles, Balanus) and small mollusks (especially periwinkles). Once inland in early Jun, largely plant material—predominantly achenes of sedges (Cyperaceae: Carex, Kobresia), some rushes (Juncaceae: Juncas), Polygon-aceae (Polygonum), Scrophulariaceae (Pedicularis), and Caryophyllaceae—found in wet, snow-free marsh areas (Nettleship 1967, 1973). By mid-Jun, plant material replaced first by spiders (dictynid spiders [Dictynidae: Dictyna]; lycosids [Lycosidae: Pardosa glacialis, Tarentula exasperans]; sheet-web weavers [Linyphiidae: Erigone, Hilaria]; crab spiders [Thomisidae: Xysticus deichmanni]) and lepidopteran larvae (tussock moths [Lymantriidae or Liparidae: Byrdia rossi]; owlet or noctuid moths [Noctuidae: Crymodes exulis]; brush-footed butterflies [Nymphalidae: Boloria]), then predominantly adult dipteran flies, especially midges (Chironomidae: many species; see Oliver 1963, 1968) by late Jun. Continuing throughout remainder of summer, foods include 5 major prey groups in addition to Chironomidae: crane flies (Tipulidae [Nephrotomia]), dance flies (Empididae [Rhamphomyia]), syrphid flies (Syrphidae; 4 species), blow flies (Calliphoridae; 3 species), and muscid flies (Muscidae; several species). Adult chironomids most important food source of adult turnstones, obtained in dry to wet habitats near ponds or streams, often along pond margins where large numbers of newly emerged chironomid adult and larvae are abundant in shoreline moss; also often pick at chironomids through ice cracks of inland ponds. Diet of young similar to that of adults, foraging with parents in marsh habitat and along slopes/shorelines of ponds; once flying, late summer, young feed almost exclusively on adult chironomids, active or dead, washed up along lake shoreline, gravel beaches, and ice fragments (Nettleship 1967, 1973). Exodus to coastal regions complete by mid- to late Aug; dominant food likely amphipods, mollusks, some insects and spiders, and rarely plant material (seeds, berries) and carrion.

Summer food habits similar elsewhere at high latitudes including Fosheim Peninsula (Parmelee and MacDonald 1960, MacDonald and Parmelee 1962) and north coast of Ellesmere I. (Feilden 1877), and nw. and e. Greenland (Manniche 1910, Løppenthin 1932, Bird and Bird 1941, Johnsen 1953, Boertmann et al. 1991).

Efficient scavengers and carrion eaters, especially early in summer when food is scarce. At arrival (late May), will feed on dead mammals (musk ox [Ovibos moschatus], collared lemming [Dicrostonyx groenlan-dicus]) and birds (King Eider [Somateria spectabilis]) and food wastes (e.g., cornmeal, meat scraps) from human habitation (Feilden 1879; Bird and Bird 1941; MacDonald and Parmelee 1962; Nettleship 1967, 1973; Meltofte 1979), as they do during migration and on wintering grounds (e.g., Selway and Kendall 1965, Mercer 1966).

Quantitative Analysis

Few detailed analyses of foraging patterns and diet in North America or elsewhere. Analysis of stomach contents of 24 adults, 3 chicks, and 5 flying young from west coast of inland Lake Hazen (Hazen Camp: 81°49´N, 71°18´W), Ellesmere I., Queen Elizabeth Is., during breeding season (1965, 1966: see Nettleship 1967, 1973) showed early-Jun diet to be largely plant material (98.3%), remainder traces of animal matter (1.7%). Late Jun little plant material (<1%), animal matter dominant (97.3%), diet comprising largely dipteran insects (60.3%, mainly adult chironomids) with lesser amounts of lepidopteran larvae (19.9%), hymenopteran ichneumonids (Ichneumonidae; 3.4%), and spiders (2.7%), relative composition that continued to mid-Jul: plant, <1%; animal, 98.7%, largely chironomid adults, larvae and pupae 77.1%. During chick-rearing (mid-Jul–early Aug), adult and chick diets similar, feeding in same habitats together employing same techniques, comprising plant material (30–32%) and dipteran insects (68–70%), mainly chironomids. Once fledged and flying (late Jul and early Aug), young separated from parents in flocks foraging along pond and lake margins almost exclusively on animal matter (>99%), mainly chironomids (82%), small amounts of lepidopteran larvae (14%), and Hymenoptera (4%).

Very selective though opportunistic within limits of foraging habitats (see Diet, above); food storage not known.

No quantitative data for summer and winter diets and usual foods. Few caloric values of invertebrate foods available at actual breeding locations of high- and low-Arctic North American turnstone populations. Values at Barrow, AK, for chironomid larvae, principal summer food of adults and young, 20.0 kJ/g dry weight, with other insect larvae (tipulids, sciarids, coleoptera) between 21.9 and 23.9 kJ/g dry weight; small adult dipteran insects measured 23.9 kJ/g dry weight, whereas adult arachnids (spiders) averaged 20.9 kJ/g (Ashkenazie and Safriel 1979).

See Behavior: self-maintenance, below.

Drinking observed rarely, edge marshy freshwater streams and ponds. Foods consumed inside and outside breeding season (mainly small insects, mollusks, crustaceans, araneids, plant seeds) produce fecal residues (liquid and solid) deficient for reliable use in identification of prey species (see Schneider and Harrington 1981, DNN), though partial or incomplete analysis possible (e.g., Harris 1979). Defecation always away from nest site; nest area remains clean until chicks appear, after which soon abandoned by adults and chicks (Nettleship 1967, 1973).