Behavior

Walking, Hopping, Climbing, Etc

Primarily terrestrial; when feeding, walk or run between pecking or probing attempts. Depending on foraging technique, walking rate varies from 3–13 cm/s at breeding and wintering areas (Baker and Baker 1973). Often stand on one leg to sleep or feed, hopping between feeding attempts, so may be mistaken for cripples (Bent 1927). Toes adapted to walking, not perching, but birds occasionally perch in small willow bushes during breeding season (CLG-T).

Flight

During nonbreeding season, often seen in large flocks, up to hundreds of thousands of birds (Hicklin 1987). Wings are narrow, straight, and pointed, for fast flight. See Migration for flight speeds.

Swimming And Diving

Swimming uncommon: rarely forage in water over tarsus depth. However, older flightless chicks readily swim if pursued, and adults can swim if necessary (CLG-T).

Preening, Headscratching, Stretching, Bathing, Anting, Etc

Perform all but anting, and in typical manner.

Sunbathing, Thermoregulation, Temperature Metabolism

Nest in sub- to midarctic areas, so > 50% daily energy requirement used in ther-moregulation and production (excluding eggs): 84–105 kJ/d in males and females, respectively. Incubating birds orient to minimize heat loss from wind convection (Ashkenazie and Safriel 1979b). In laboratory, individuals are unable to maintain normal internal temperature below –18° C. Resting metabolic rate estimated at 10.7 + (–0.2 + 0.03)° C (Norton 1973).

Sleeping And Roosting

During breeding season, usually sleep after feeding bouts, which may aid digestion (Ashkenazie and Safriel 1979b). At migratory staging areas, thousands may gather in mixed-species roosts. Roosting behavior (often head tucked under wing, standing on one leg) common when feeding not possible, at high tide or on dark nights (CLG-T).

Daily Time Budget

Daily time budget constructed at Barrow, AK, during breeding season (Ashkenazie and Safriel 1979b). Unpaired males spent 15% time in flight display, virtually none the rest of the season. Incubation or brooding behavior up to 14% during laying, almost 50% in each sex during incubation and early brooding, declining to almost nothing in second week after hatching. Females spent > 60% of time feeding before incubation and in week 2 after hatching, decreasing to 40% during incubation and first week after hatching. Feeding less in unpaired territorial than paired males (30% vs. 45%), 40% (as in females) during incubation and early brooding, and 50% during late brooding. Calling and alertness highest in unpaired males (12%). Walking and ground displays varied from 3% to 16% throughout season; lowest during incubation and late brooding. Standing least during incubation and early brooding (2% and 7%), and most in laying and late brooding males (26% and 34%). Both sexes spent 1% to 8% of time preening and washing, and 1% to 3% in normal flight. Sleeping most common before laying (13%) and least during brooding (0%). After breeding season, flocked birds of both sexes spent almost all of their time foraging (88%) and sleeping (8%); normal flight, walking, and preening made up remaining 4% (Ashkenazie and Safriel 1979b).

Physical Interactions

Even during the nonbreeding season, individuals engage in aggressive behavior such as threat displays, displacement of other birds, chasing, and fighting (Recher and Recher 1969). Aggressive birds often rush at one another, with neck feathers standing out in ruff, wings half spread, and tail elevated (Brandt in Bent 1927, Harrington and Groves 1977). Not known if sexes differ in intensity of aggression.

Aggressive interactions usually common at migratory stopovers (Recher and Recher 1969, Harrington and Groves 1977, Young 1989, CLG-T), but see Burger et al. (1979). Aggression during breeding season is mainly associated with territoriality and courtship, while during migration primarily between foraging birds. Intraspecific aggression is most common, then aggression with morphologically similar species (e.g. Least Sandpiper, C. minutilla). Intensity of aggression usually increases with frequency of aggression and population density, but declines at high densities, usually owing to high food abundance in area. When hunting prey visually, aggression is usually higher than when foraging by probing. Migrants that hold foraging territories are more aggressive than those without (Recher and Recher 1969). In one study, juveniles were more aggressive than adults (Harrington and Groves 1977).

Threat And Appeasement Displays

Threat displays not described in detail. No information on appeasement displays.

Individual distance during nonbreeding season varies, being greatest in patchy foraging habitat or where food is scarce (Recher and Recher 1969).

Males arrive on breeding grounds a few days before females, and establish a territory via flight displays and chases (CLG-T; see Sounds: vocalizations). Males normally reestablish same territory as previous year. Territory size may vary among areas: near Churchill, Man., territories averaged one ha (Gratto et al. 1985). Territories (particularly those on small islands) often remain stable until late in brooding period; others break down shortly after hatching. Both sexes defend territory during incubation. Most foraging apparently occurs off territory, up to 2–3 km away (Ashkenazie and Safriel 1979a, CLG-T). Territory maintained primarily against conspecifics, but in Churchill area, Least Sandpipers were always attacked, while Dunlin (C. alpina) were not (CLG-T). Least Sandpipers normally nest in different habitat than Semipalmated Sandpipers: Least Sandpipers in high willow, dry areas versus Semipalmated Sandpipers in low willow, wetter areas. During migration as well, Least Sandpipers primarily forage in marsh habitats, while Semipalmated Sandpipers feed mainly along shore (Recher 1966).

Territoriality noted during nonbreeding season in juveniles in Alaska (Myers et al. 1979), and in foraging adults and juveniles during fall migration (Recher and Recher 1969, Lank 1983, Morrison 1984). Nonbreeding territoriality depends on environmental conditions, being most common in patchy environments where foraging sites limited, or prey patchily distributed (Recher and Recher 1969).

Dominance Hierarchies

In nonbreeding season, dominant individuals initiate chases, and adults are not necessarily dominant to juveniles (Harrington and Groves 1977). Displacement of territorial male never noted during breeding season (CLG-T).

Mating System

Monogamous and territorial: probably primitive pattern of sandpiper social systems. Both sexes incubate, and nesting densities are relatively stable from year to year (Pitelka et al. 1974).

Pair Bond

Unpaired males engage in aerial displays of hovering flight with rapid wingbeats, accompanied by vocalizations. Mean flutter rate 17.9/min in Manitoba, 41.2 in Alaska (Miller 1983), and 23.5 in Alaska (Sordahl inMiller 1983). Average duration of display flight 1.7 min (SE 0.24) in Alaska, 1.6 min (SE 0.12) in Manitoba (Miller 1983), and 0.9 min (SE 0.24, n= 12) in Manitoba (J. Reynolds and C. Gratto-Trevor unpubl. data). Flight display is thought to attract females to territory, and repel competing males (see Sounds: vocalizations).

Females are attracted to territory, then selected by territorial male. Savile (1951) described courtship display where pair chased each other, buzzing and chittering, often both with tails cocked. Pursuer often stretched one or both wings vertically, sometimes raising crown feathers, and followed other into small scrape in the ground, then continued chasing, and finally attempted copulation. Male follows mate almost constantly before incubation except for occasional territorial encounters or displays (Ashkenazie and Safriel 1979a).

Pair bond, once formed, remains intact until nest loss, or shortly before or after hatching. If nest loss occurs early in season, individuals often renest, normally with previous mate. Only one instance of intraseason “divorce” (where both birds were still known to be alive) was recorded in eight years in Manitoba (CLG-T). Female usually deserts brood shortly after hatching and migrates south earlier than her mate (Safriel 1971, Ashkenazie and Safriel 1979a, b, Gratto-Trevor 1991). Males arrive on breeding grounds several days before most females: no evidence they winter together. In many cases, however, mates reunite the following year, as long as both survive and return to the area (up to 4 years known). Fifty percent of birds returning reunite with previous mate. On average, only 20% “divorce,” i.e., do not reunite even though previous mate returned (Gratto et al. 1985, CLG-T).

No evidence that reuniting pairs have higher nesting success, and their nests hatched only 1.6 days earlier (on average) than those of new pairs (Gratto et al. 1985, Gratto-Trevor 1991).

Extra-Pair Copulations

No information.

During breeding season, little evidence of sociality, although breeding territories appear clumped in available habitat (Norton 1973). On migration or wintering grounds, often in large mobile foraging or roosting flocks of up to several thousand birds (Hicklin 1987). Intraspecific aggression common in foraging flocks (see: Agonistic behavior). Foraging flocks may consist of other shorebird species.

Potential predators of eggs and young include jaegers (Stercorariusspp.), Northern Harriers (Circus cyaneus), gulls (Larusspp.), Short-eared Owls (Asio flammeus), Snowy Owls (Nyctea scandiaca), Black Turnstones (Arenaria melanocephala), Sandhill Cranes (Grus canadensis), weasels (Mustelaspp.), and arctic (Alopex lagopus) and red foxes (Vulpes vulpes) (Norton 1973, Gratto et al. 1983, R. Gill pers. comm.). Egg loss to predators is apparently related to microtine numbers; in years of few small mammals, most predators switch to shorebird eggs and young (Norton 1973,CLG-T).

Apparent nest success (nests where at least one young hatched) varied from 24% to 70% (average 50%) over 8 years at La PÈrouse Bay, Man. (Gratto et al. 1983, Gratto 1983, Gratto and Cooke 1987, CLG-T). Most nest loss (on average 86%) was due to predation, and the remainder to parental desertion (usually of very late nests). Known partial clutch loss was found at 5%–17% (average 11%) of nests. In another study near Churchill, Man., all eight nests hatched (Jehl 1971). In four years near Barrow, AK, clutch loss due to predation averaged only 25% (Safriel inNorton 1973), and was never higher than 30% (Safriel 1971). In another Alaskan study, however, hatching success was 7%, with all loss due to arctic foxes (Erckmann 1981). Unattended clutches may survive better (Safriel 1980) or worse (Erckmann 1981) than normally attended ones, perhaps depending on the type of predator involved, and whether they locate nests by sight or smell.

Jaegers and Glaucous Gulls (Larus hyperboreus) take many young sandpipers (Norton 1973, Safriel 1975). Parasitic Jaegers (Stercorarius parasiticus) also take adult sandpipers. During migration, Peregrine Falcons (Falco peregrinus) and Merlins (F. columbarius) often attack shorebird flocks. When flocks are attacked by an avian predator, sandpipers respond by circling high. When solitary during breeding season, they crouch to avoid avian predators (CLG-T).

When approached by a predator during late incubation, adults sit tight. If flushed close to their nest, they often perform distraction displays such as the rodent run, but there is much individual variation in departure distance and intensity of distraction display. Distraction displays while guarding brood involve noisy circling (see Sounds: vocalizations), and rodent run displays (Kuzyakin in Gochfield 1984, CLG-T).