Breeding

Pair Formation

See Fig. 3. Arrive on breeding grounds in Manitoba and Alaska in last week of May or early June (Dixon 1943, Littlefield and Pakulak 1969, Ashkenazie and Safriel 1979a, CLG-T). Males normally precede females by less than a week, and set up territories almost immediately (CLG-T). Most pairs form shortly afterward (Ashkenazie and Safriel 1979a), although some new birds appear late and pair then, if possible (CLG-T).

Nest Building

Pairs engage for several days in nest-scraping, where males create numerous scrapes.

First/Only Brood Per Season

First egg may be laid 4 to 6 days after pair formation (Ashkenazie and Safriel 1979a). Timing of egg laying appears dependent on availability of invertebrate prey, as laying can be delayed for several weeks in inclement weather. In two years of severe weather at La Pérouse Bay, Man., approximately half of paired females did not lay clutches (Gratto-Trevor 1991).

First egg in Manitoba, Alaska, and Victoria Island, NWT: 2 to 20 June (Brandt 1943, Dixon 1943, Parmelee et al. 1967, Ashkenazie and Safriel 1979a, CLG-T). Peak nest initiation usually third week in June (Parmelee et al. 1967, Ashkenazie and Safriel 1979a, Gratto and Cooke 1987). Although snow melt averages almost a month earlier at La Pérouse Bay, Man., than Barrow, AK (18 May versus 12–17 June), laying occurs at the same time in both areas. Peak insect hatch also occurs at the same time in both areas (McClure 1943, Holmes and Pitelka 1968).

Late arrivals and renesting attempts may extend nest initiation period to early July. Clutches initiated later than 1 July often deserted late in incubation (CLG-T).

Earliest hatch in last few days of June (Brandt 1943, Dixon 1943, CLG-T), after 20 days of incubation. Peak hatch normally second week in July (Norton 1973, Gratto and Cooke 1987). Most chicks fledge in late July, at 16–19 days of age (Safriel 1975, Gratto-Trevor 1991).

Second Brood Per Season

Never observed to lay or incubate two clutches in one season, unless first clutch predated or deserted early in breeding season (CLG-T). Renests can be laid as soon as 5 days after clutch lost (Safriel 1971). Because Manitoba nests due to hatch after 24 July are often deserted, less than two weeks are available from completion of first clutch to initiation of renest (CLG-T).

Breeding endocrinology was examined in Manitoba. Seasonal patterns of circulating steroid hormones as expected for male-territorial monogamous bird. Testosterone levels higher in males than females, particularly during prelaying, and decline in both sexes from prelaying to brooding. Progesterone highest in prelaying females. No significant difference in estradiol levels between sexes, but levels in females decrease from prelaying to brooding (Gratto-Trevor et al. 1990a). High prolactin levels correlated with persistent incubation behavior, increasing greatly at onset of incubation. Circulating prolactin levels, however, do not explain earlier brood desertion of females. Contrary to previously studied species, prolactin levels do not decline in either sex after chicks hatch (Gratto-Trevor et al. 1990b). Blood sampling stress appears to have little effect on mortality, nest desertion, and return rate of the birds (Colwell et al. 1988b), but does affect circulating hormone levels, apparently elevating low levels and depressing high levels slightly (Gratto-Trevor et al. 1991).

Selection Process

Males establish territory, normally the same as previous year, before females arrive (Gratto et al. 1985). Males may make scrapes before pair formation, as well as after. Females select scrape.

Microhabitat

No information.

Site Characteristics

In river deltas in Manitoba and Alaska, often nest at top of small islands or hills, usually under small willow (Salix) bush, or in damp areas along island edges, in grass or Carextussocks. Nest sites generally drier than those of Dunlin and Red-necked Phalaropes, which nest in same habitat (R. Gill pers. comm., CLG-T). Farther north, most nests in Carexmarshes, pockets of Carexin rocky areas, grassy hummocks in peaty areas, and among creeping berry plants, but not on barren sandy flats or rocky ridges (Brandt 1943, Savile 1951, Parmelee et al. 1967).

Construction Process

Nest scraping displays common in prelaying birds, where males make scrapes by pressing breast against ground and rotating body. Female examines scrapes and lines one with small leaves or grass using sideways building display, by sitting in nest cup and throwing lining material over back. Copulation occurs after nest selection. Female continues to add lining material throughout laying period (Ashkenazie and Safriel 1979a).

Structure And Composition Matter

Nest mere depression in ground, lined with dead willow, dwarf birch (Betulaspp.) or cranberry leaves (Oxycoccusspp.), and pieces of grass, sedge or moss (Brandt 1943, Savile 1951, Parmelee et al. 1967).

Dimensions

Inside diameter is 5–6 cm, inside depth 4–5 cm (Brandt 1943).

Microclimate

No data.

Maintenance Or Reuse Of Nests, Alternative Nests

Previous year’s nest cup sometimes reused if young successfully hatched there. Old nest cups often rescraped but not reused. Occasionally use nest cups of other pairs (if other birds not present), or even those of other species such as Dunlin, Red-necked Phalarope, Horned Lark (Eremophila alpestris), and Savannah Sparrow (Passerculus sandwichensis; Gratto et al. 1985). Site of depredated nest not reused by same birds in same year (CLG-T).

Nonbreeding Nests

Nest cup provided by male for brooding chicks each night for first 6–8 days after hatch (Ashkenazie and Safriel 1979a).

Shape

Ovate pyriform to subpyriform (Bent 1927, Brandt 1943). Because of pyriform shape, with small ends together, 4 eggs of clutch fit together snugly in nest cup.

Size

Eggs of adult pairs in Manitoba: n= 310, length 30.0 ± 0.9 mm, breadth 21.3 ± 0.5 mm, calculated volume (length x breadth²) 13.6 mm³. Eggs at nests of yearling females smaller in length but not breadth (Gratto et al. 1983). Runt eggs, such as described by Manningand Carter (1977: 22.2 x 16.1, 42% normal volume) rare; none noted in Manitoba among > 1,800 eggs examined (CLG-T).

Average mass of fresh egg 7.3 g near Barrow, AK, dry weight excluding shell 1.5 g, and 46% fat (MacLean 1969). Mass of fresh egg in Manitoba averaged only 6.3 g (CLG-T). Calcium content of clutch twice that of prelaying female (MacLean 1974). Mass of an egg 22%–25% of average female mass (28.7 g, both Alaska and Manitoba; Ashkenazie and Safriel 1979b, Gratto 1983). Therefore, weight of 4–egg clutch = 88%–100% of female’s weight.

In eggs collected from 1914 to 1947 in Alaska, mean egg thickness index ± SE = 0.46 ± 0.002 mm (99 eggs of 26 clutches), and from 1951 to 1965, 0.46 ± 0.004 mm (77 eggs of 20 clutches): no difference between periods (Morrison and Kiff 1979).

Color

Color and pattern of eggs extremely variable among clutches, even in single breeding area (CLG-T). Not known whether patterns are consistent for individual females. Eggs cannot be definitely distinguished from those of Least or Western sandpipers, as measurements, coloring, and markings intergrade with both (Bent 1927, Gabrielson and Lincoln 1959).

Ground color varies from dull white to pale olive buff and olive buff, occasionally to deep olive buff or isabella color. Markings liver brown to chestnut brown in darkest, and hazel to cinnamon brown in lightest. Markings often have spiral tendency, particularly at large end of egg, but many spots round instead of elongate. Underlying markings light quaker drab to quaker drab (Bent 1927, Brandt 1943).

Surface Texture

Smooth and glossy (Harrison 1978).

Egg Laying

Some energy for egg production acquired during migration (MacLean 1969), but more must be obtained on breeding grounds. First egg can be laid 4–6 days after pairing (Ashkenazie and Safriel 1979a), if food available, otherwise laying may be delayed for as much as two weeks, and some paired females may not lay at all in some years (Gratto-Trevor 1991). Eggs deposited 1/day, often in morning, evening or night (Ashkenazie and Safriel 1979a), occasionally up to 32 h between eggs. Clutch (almost always four) normally laid in 4–5 days. Females do not store calcium in medullary bone, but acquire it from insect prey and ingestion of small mammal bones. After laying, females contain less calcium than males or prelaying females, and decalcified areas are often visible in their skulls (MacLean 1974).

Males normally follow females during the laying period, from feeding to nest sites, except for occasional territorial displays and short spells of incubation (Ashkenazie and Safriel 1979b).

No evidence for replacement of eggs destroyed during laying. In all instances where an egg is broken before laying of third or fourth egg, broken egg is removed, and final clutch size is only three. Intraspecific egg dumping never observed, and never more than four eggs of this species in almost 600 nests examined (CLG-T).

Onset Of Broodiness And Incubation In Relation To Laying

Partial incubation by both sexes during laying, with continuous incubation several hours before laying of last egg (Ashkenazie and Safriel 1979a).

Incubation Patches

Incubating males and females have two large oblong incubation patches, one on either side of midline.

Incubation Period

Usually 20 d, occasionally up to 22 d (Safriel 1971, CLG-T).

Parental Behavior

Males and females incubate equally. Incubating bird rolls eggs and camouflages nest (by bending vegetation over nest), while remaining alert (Ashkenazie and Safriel 1979a).

No obvious sex differences in daily incubation rhythm; neither sex more likely to incubate at particular time of day or night (Norton 1972, Gratto-Trevor 1991). Incubation bouts 3–5 h early in incubation, and gradually increase up to 13–14 h (Ashkenazie and Safriel 1979a). Daily nest attendance can vary from 80%–100% during a day, being lowest in afternoon. When one adult was experimentally removed, attendance dropped to 35% in morning and 60% in afternoon. Remaining parent almost always deserted before hatching (Erckmann 1981). If one adult is killed by a predator before eggs pip, remaining parent almost always deserts within five days (Gratto-Trevor 1991).

With both parents present, mean number of absences per day was seven (range 4–13), with mean duration of absence 21 min (2–164) in Alaska (Erckmann 1981).

Hardiness Of Eggs

Embryonic resistance to chilling is maximal before incubation (Norton 1972). Tolerance to cold exposure is substantial even during incubation, but hatchability of eggs can be affected if chilling is prolonged, especially late in incubation (Erckmann 1981). When fifth eggs were experimentally introduced, they failed to hatch unless the shape of the nest cup was changed (Safriel 1980). Configuration of four pyriform eggs appears most efficient in retaining heat during incubation (Norton 1972).

Preliminary Events And Vocalizations

Shortly before hatching, once eggs begin to pip and chicks can be heard peeping and tapping on the shell with egg teeth, parental behavior changes. Incubating bird usually sticks closer to nest, displaying and vocalizing more readily when disturbed (CLG-T).

Shell Breaking And Emergence

Chicks can hatch at any time of day. Duration of hatching of egg from first star pip to damp chick can be more than three days or less than two, but usually two to three days. Once egg has “hole-pipped,” the chick hatches in < 12 h. All eggs of a clutch usually hatch within one day, occasionally two (Ashkenazie and Safriel 1979a, CLG-T). Parents rarely desert a pipped egg even if all others have hatched, and often remain incubating even unpipped eggs for several days after remainder have hatched (CLG-T).

Parental Assistance And Disposal Of Eggshells

Parents not known to assist hatching of chicks. If shell crushed when egg pipping, shell not removed by parent, and chick dies. Eggshells removed by parent almost immediately after hatching, rarely found near nest (CLG-T).

Condition At Hatching

Average mass (± SE) of day-of-hatch chicks in Manitoba = 4.4 ± 0.04 g (n= 114); wing length 12.9 ± 0.13 mm; bill length (culmen) 7.8 ± 0.05 mm; tarsus 19.6 ± 0.08 mm; no remiges visible. Wing about 13% of adult, bill 38%, weight 16%, and tarsus 89% (CLG-T).

Covered in down at birth, with irregular dark brown markings on head and “hour-glass” shaped figure on back (Jehl 1968). Natal down white on forehead, sides of head, and all underparts; faintly washed with pale buff on upper breast and cheeks. Median stripe on forehead partway to bill, broad loral stripe, malar stripe, and spot in center of crown are all black. Back, rump, wings and thighs a mix of hazel and black, finely dotted with white terminal tufts (Bent 1927). Legs and bill black, bill bluntly tipped, eyes open at hatching. Egg tooth lost in first day after hatching (CLG-T).

Within a few hours of hatching, chicks stumble from nest cup and peck for insect food (Ashkenazie and Safriel 1979a).

Growth And Development

Mass increases rapidly until about 11th day after hatch, then more slowly (Safriel 1975, CLG-T). Bill also grows fastest in first 11 days, then more gradually. Wing length increases slowly until about day 7 (when primaries begin to appear), then rapidly to day 20, and again more slowly. Tarsus increases slowly to full adult size (CLG-T).

Primary pin feathers visible about third day after hatching. Primaries, secondaries, tertials, scapulars, wing coverts, and upper back all in pin stage by day 5 or 6. Head and breast in pin stage by day 8, and flight feathers begin to emerge. By day 10, tail and belly in pin stage, and by day 15, primaries sufficiently emerged to allow flight. By this time down present only on back of neck and head, under throat and by bill. Black rump stripe and white throat now evident. Primaries about 90% emerged by day 22, little down present, and Juvenal plumage nearly complete (CLG-T).

At day one, young birds preen, exercise wings, and crouch when warned by parents (Ashkenazie and Safriel 1979b). As chicks age, they are more likely to run than crouch, and swim readily if pursued. Chicks vocalize when chilled, especially when very young. No evidence of intersibling conflict (CLG-T).

Brooding

Young feed themselves within hours of hatching, but are often brooded by parent for first week, and guarded constantly for first two weeks. For first 4–5 d after hatching, chicks are brooded every 3–7 min for 3–7 min, and males provide new scrape each night for brooding. Amount of brooding decreases substantially in second week (Safriel 1971, Ashkenazie and Safriel 1979a, b). In Alaska, adults spent 70% of time brooding and guarding chicks, and only 30% foraging, when young < 7 days; when chicks 10 days old, 70% of parental time spent foraging and only 30% in alertness, distraction displays, and brooding (Erckmann 1981).

Females normally desert brood 0–11 d after hatching, earlier if nest hatches late in season and later if nest early. In Manitoba, 86–97% (average 91%) of females desert mates each year after hatching; in remaining 3–14% (average 9%), male deserts female. In Alaska, all females apparently desert; one was observed being chased away by mate. Females may have an energy deficit after laying, and desertion of brood may increase female survival. Males desert brood shortly before or after fledging, on average 8 d after females (Safriel 1971, Ashkenazie and Safriel 1979a, b, Gratto-Trevor 1991). Average survival of young higher in normal 4-chick broods compared to experimental 5-chick broods. Single attending parent apparently less able to care for more than four young (Safriel 1975).

Feeding

Young not fed by parents. Chicks forage by pecking at small adult dipteran insects when very young, and mostly insect larvae when older (Holmes and Pitelka 1968).

Nest Sanitation

Chicks desert nest within a day of last chick hatching (Ashkenazie and Safriel 1979a, CLG-T).

Parental Carrying Of Young

Never observed.

Never observed.

Not reported. One nest with 6 eggs, including 2 Red-necked Phalarope eggs, was incubated by Semipalmated Sandpipers (one a yearling); not known which eggs were laid first (Gratto et al. 1983).

Departure From The Nest

Parents lead chicks from nest within hours of hatching. In Manitoba, if nesting on small island, birds may remain until near fledging. If on large island or mainland, parents may move chicks up to 1 km to larger water bodies, particularly coast (CLG-T). In Alaska, brood usually moved after female leaves, and second home range established up to 3 km away (Ashkenazie and Safriel 1979a).

Growth

Young fly slightly 14–15 d after hatching; capable of sustained flight at 16–19 d (Safriel 1975, Gratto-Trevor 1991). At fledging, young have 80% of adult wing length, 90% bill length, 100% tarsus length, and 90% mass (CLG-T).

Association With Parents Or Other Young

See Parental care. Brood usually remains together until deserted by parents. Chicks may be adopted by other parents if broods mix (CLG-T).

Ability To Get Around, Feed, And Care For Self

Young deserted by both parents as early as 10 days of age have been known to fledge successfully (CLG-T).

Juveniles migrate southward several weeks after most adults, and most overwinter in South America. There they undergo Prebasic molt of body feathers and some flight feathers (see Appearance: molts and plumages). Approximately two-thirds of all juveniles do not migrate northward to breed as yearlings, but spend boreal summer on wintering grounds (Gratto and Morrison 1981, Spaans 1984). In a northern breeding area near Barrow, AK, individuals apparently do not breed as yearlings (Safriel 1971, Safriel inMyers 1981), but in an area 1400 km farther south, near Churchill, Man., 1%–10% of all breeders each year are yearlings (Gratto and Cooke 1987).