Breeding

Pair Formation

Arrives on breeding grounds in Manitoba last week of May or early Jun (MSB), Queen Charlotte Is. early May (Cooper and Miller 1997), and Prudhoe Bay, AK, early May (R. Lanctot pers. comm.). Males previously banded on study area in Churchill, Manitoba, arrive first. Males set up territories soon after arrival; pairing with females quickly follows.

Nest-Building

Begins 5–10 d after arrival, when females arrive on territories.

First/Only Brood Per Season

Figure 4 . One brood per season. Two to 8% renest after nest loss (EN), with 7 d between nesting attempts (Y. Zharikov pers. comm.).

Timing of egg-laying depends on conditions: snowfall and temperature, and their effect on invertebrate numbers. In Churchill, Manitoba, in 1992, temperature was significantly lower than in other years during egg-laying period; egg-laying was delayed (Nol et al. 1997). In Churchill, eggs are laid between 5 Jun and 8 Jul (Nol et al. 1997, Y. Zharikov pers. comm.). On Queen Charlotte Is., earliest nest seen 5 May, most mid- to late May; hatching 13 Jun–20 Jul, most late Jun and early Jul (Cooper and Miller 1997). First flying juveniles in late Jul at Churchill. On Baffin I., eggs are laid mid-Jun (Soper 1928), and most young fledge early Aug (Sutton and Parmelee 1955); in Mackenzie Delta, eggs are laid early Jun and hatch end of Jun to first 2 wk of Jul (C. Gratto-Trevor pers. comm.).

Selection Process

In Churchill, Manitoba, males establish territories shortly before pairing. Males make new scrapes and use preexisting scrapes. Females sit in scrapes during courtship (see Behavior: sexual behavior, above). Females sitting in scrapes may be a means by which nests are chosen (MSB).

Microhabitat

In Churchill, Manitoba, mean percentage of ground cover at nest site (n = 32): lichen or moss, 21.7% ± 14.00 SD; stone or gravel, 36.3% ± 26.21 SD; dwarf shrubs, 23.3% ± 15.2 SD; woody, nondwarf shrubs, 5.5% ± 9.53 SD; herbaceous, nonlichen vegetation, 8.4% ± 14.7 SD; exposed soil, 1.9% ± 6.05 SD; debris 3.0% ± 5.21 SD). Slope of nest is between 0 and 10° (n = 22; Robinson 1998). Visibility is 100% close to nest, declining away from nest (Sullivan Blanken and Nol 1998).

Site Characteristics

Nests in varied locations from sandy, gravel-shale exposed areas to grassy-tundra areas (see Habitat, above). On coast at Churchill, Manitoba, nests on dry tundra (Robinson 1998). Three nests in Churchill found in forested areas, unusual for this species (MSB, EN). On Queen Charlotte Is., British Columbia, nests on sand beaches above high-tide line among drift logs or protruding ends of logs or planks (Cooper and Miller 1997).

Construction Process

Male scrapes by pressing breast to ground and kicking legs out behind. Lines nest by tossing material into it from up to 1 m away, while walking away after scraping nest cup. Both females and males have been observed during incubation throwing nest material and pecking at sides of nest throughout incubation.

Structure And Composition Matter

Shallow depression in gravel or sand, lichen, or moss, lined with most prevalent material around nest site: White mountain-avens (Dryas integrifolia) leaves, willow leaves, shell, rock, sand, grass, glass, charcoal, debris (Sullivan Blanken 1996), sometimes in moss or dead seaweed (Bent 1929). Of 32 nests for which substrate was determined in Churchill, Manitoba, 21.9% on lichen or moss, 6.3% on woody, nondwarf shrubs, 25% on dwarf shrubs, 9.4% on herbaceous vegetation, and 37.5% on stones or gravel (Robinson 1998). Building materials in Churchill were mostly woody debris (70.6–93.3% of total nests) leaf litter (94.1–100%); less often herbaceous plant stalks (20–64.7%), lichen moss (40–60%, n = 32 nests; Robinson 1998).

Dimensions

Nests in Churchill, Manitoba: mean diameter across top (level with surrounding substrate) 91.1 mm ± 11.16 SD (n = 22; C. Robinson pers. comm.); depth in center 2.8 cm ± 0.68 SD (range 1.35–4.8, n = 34; MSB). Nests often have vertical sides and same depth throughout bottom of nest cup; distinctive from nests of Piping Plover or Killdeer with gradual sloping sides (EN). Nests usually on flat slope, not on a ridge, and flat or convex microsite (Robinson 1998).

Microclimate

Average air temperature at inland nest sites (>1 km from coast) was 1°C higher than at coastal nest sites (<1 km from coast) in Churchill, Manitoba, in 2 yr: (e.g., in Jul 1997, inland 15.5°C ± 7.27 SD, coast 14.4°C ± 7.44 SD, n = 10 at each location; Robinson 1998, Sullivan Blanken 1996). Wind speed higher at coast (from 30 cm above ground, inland 288.2 cm/s ± 90.4 SD; coast 325.4 cm/s ± 88.6 SD; n = 10 at each location measured simultaneously). Insolar radiation (W/m²) not significantly different: inland 288.2 ± 271.4 SD; coast 290 ± 285.1 SD (n = 10 at each location; Robinson 1998). Nest sites low enough to be sheltered from wind; always in full sun.

Maintenance Or Reuse Of Nests, Alternate Nests

Reuse of 1 nest site reported in successive breeding seasons, in Churchill, Manitoba.

Nonbreeding Nests

No evidence of nonbreeding nests.

Shape

Short ovate pyriform to subpyriform.

Size

In Churchill, Manitoba (1988–1995), mean length ranged from 32.4 mm ± 0.2 SE to 33.1 mm ± 0.1 SE (n = 187); mean breadth 22.8 mm ± 0.1 SE to 24.1 mm ± 0.1 SE (n = 187; Nol et al. 1997). Laying order did not affect egg size (n = 7 clutches; Nol et al. 1997). Not known whether size is variable across geographic range.

Mass

In Churchill, Manitoba (1988–1995), mean 8.7 g ± 0.1 SE to 9.4 g ± 0.1 SE (n = 174; Nol et al. 1997). Percentage of female mass = 18.2.

Color

Slightly glossy. Light brown, clay color, to pale, olive buff background, with small or large blotches of black, brownish black, or very dark browns; some heavily blotched with chestnut brown or sepia; usually a few small underlying spots of pale drab gray (Bent 1929). Markings sometimes more concentrated toward larger end, more heavily marked than eggs of Common Ringed Plover (Baicich and Harrison 1997).

Surface Texture

Smooth (MSB).

Eggshell Thickness

Thickness index (shell weight × 100)/length × breadth) declined 1.61%, probably not biologically significant, from early (1931–1945) to late (1948–1953) period: early, 0.62 ± 0.006 SE (n = 58 eggs, 15 clutches) late, 0.61 ± 0.08 SE (n = 26 eggs, 8 clutches; Morrison and Kiff 1979).

Clutch Size

Usually 4 eggs, sometimes 3, rarely 2 (Table 1; Bent 1929). Lower clutch sizes in Churchill, Manitoba, appear to occur in extremely cold breeding seasons. Clutch size in Queen Charlotte Is., British Columbia: mean 3.79 (median 4, n = 71); did not vary within season (Cooper and Miller 1997).

Egg-Laying

Interval between laying of eggs is about 24–30 h in Churchill, Manitoba; 1 egg/d (Sutton and Parmelee 1955, MSB). Clutch is completed within 5 d. Only males are seen at nest dur-ing laying, and sometimes when only 1 egg in nest (7 nests, males at all 7; EN). Laying is delayed during colder conditions, presumably owing to lower food supply (Nol et al. 1997). Egg-dumping not reported.

No evidence of egg replacement for destroyed eggs or broken eggs. Broken eggs are removed from nest; dinged or dented eggs are not always removed (MSB). Intraspecific egg-dumping not observed; never >4 eggs in a nest in Churchill, Manitoba (MSB), and egg-dumping not observed elsewhere.

Onset Of Broodiness And Incubation In Relation To Laying

Partial incubation mostly by male during laying (EN). Continuous incubation may not occur until clutch is complete and occasionally after clutch is complete; eggs were found unattended and cold in Churchill, Manitoba, after clutch completion. Broodiness increases as clutch ages, and rarely is nest unattended 5 d after clutch completion (MSB).

Incubation Patches

Two large oblong incubation patches on either side of midline on both males and females. Develop slowly during first 5 d after clutch completion.

Incubation Period

Lasts about 24 d (average 24.2 d, range 23–25, n = 5; Y. Zharikov pers. comm.).

Parental Behavior

Males appear to be in attendance most of the time during egg-laying (see Eggs, above), while females are foraging nearby (EN). Males and females share nest attendance equally after clutch is completed; incubate throughout day, with males incubating during darkest hours in Churchill, Manitoba (Sullivan Blanken and Nol 1998). Males incubate between 12:00 and 02:30 also on Southampton I., Northwest Territories, where there is no complete darkness during incubation (M. Williamson pers. comm.). Males and females switch nest attendance every 2–4 h throughout incubation; longer bouts (321 min) between 23:00 and 04:00 in Churchill (see Behavior: self-maintenance, above; Sullivan Blanken and Nol 1998). Only 2 nest desertions reported in 2 yr in Churchill, both when nesting was delayed (Nol et al. 1997), 1 of which the male remained in up to 5 d before deserting (MSB). During banding, males and females are equally likely to return and enter nest trap.

Time budgets for Churchill, Manitoba: Males and females share incubation nearly equally (Sullivan Blanken and Nol 1998). Each adult spends 45% of time incubating, alternating on average every 98–321 min (n = 24); female’s shifts are slightly shorter than male’s (p = 0.07), and nocturnal shifts are longer than daytime shifts (p = 0.0001; female day, mean 98.4 min ± 15.2 SE, n = 8; female night, mean 247.8 min ± 30.4 SE, n = 5; male day, mean 136.0 min ± 20.6 SE, n = 8; male night, mean 321.1 min ± 52.3 SE, n = 3; Sullivan Blanken and Nol 1998). Spent 0.17% of time preening while on nest, 4% while tending chicks (Sullivan Blanken 1996). Incubating adults spent 0.29% of their time walking, 3% moving on nest, 0.15% head-bobbing, and 0.32% of their time flying off nest, usually flying only to leave nest when predator approached. While incubating, parents spend greatest amount of time looking, a semialert behavior, relaxing, neither alert nor sleeping, and with bill in their scapulars. Parents nesting at more open coastal nesting sites in Churchill, Manitoba, exhibited significantly fewer vigilant behaviors than inland parents. Males and females did not differ in either frequency or duration of behaviors while incubating (Sullivan Blanken and Nol 1998).

Hardiness Of Eggs Against Temperature Stress; Effect Of Egg Neglect

Bout of 10 min off nest by incubating female at 6.8–7.5°C, with rain and wind, resulted in drop in temperature of egg fitted with thermistor, from 35.7 to 17.6°C (M. Williamson pers. comm.). Eggs hatched. Egg temperatures dropped from 37.3 to 24.8°C while incubated during a thunderstorm, and eggs hatched (M. Williamson pers. comm.). Before incubation commences, eggs have been observed unattended for longer periods than 10 min, and hatching resulted (MSB). Eggs can better withstand cold temperatures before incubation commences (Norton 1972). Eggs with slight dent can be sealed with water-soluble paint and still hatch (Y. Zharikov pers. comm.).

Preliminary Events And Vocalizations

In Churchill, Manitoba, eggs hatched at any time of day or night (MSB). Period of egg-starring to pipping of hatching eggs can last 2–5 d. Peeping of unhatched chicks is audible as much as 3.5 d before hatching (Sutton and Parmelee 1955, MSB).

Shell-Breaking And Emergence

Once egg has been “hole-pipped,” usually hatches within 12 h, but sometimes as long as 4 d (Sutton and Parmelee 1955). Eggs hatch synchronously (Nol et al. 1997), but 1 egg, usually the last one laid, may hatch a day later (Sutton and Parmelee 1955, MSB). In such cases, female continues to incubate while male takes chicks a short distance away to brood and feed. Female or male may also brood chicks in nest cup at this time. Desertion of unhatched, viable eggs—with peeping chicks inside—occurred only in 1992, the latest year for nesting measured in Churchill, Manitoba (Nol et al. 1997, MSB).

Parental Assistance And Disposal Of Eggshells

Parents do not assist chicks in hatching. Eggshells are removed promptly after egg hatches, sometimes to within 10 m of nest (Y. Zharikov pers. comm.), but they are usually not found.

Condition At Hatching

In Churchill, Manitoba, average bill length of chicks on day of hatching is 6.42 mm (range 5.2–7.6, n = 81), tarsus 17.04 mm (range 13.6–19.0, n = 83), and mass 6.64 g (range 5.0–8.1, n = 84; MSB). Similar mass reported in Churchill by Ricklefs (1984): 6.41 g ± 0.62 SD (n = 22). Chicks are wet at hatching, occasionally with protruding yolk sac; typically dry within 1 h (Bent 1929, MSB). Downy at hatching; mottled buff and black above and white below, with white spot below eye; distinct black stripe from bill to eye and from lores to auriculars. Broad black band encircles back of neck (Bent 1929).

Growth And Development

From Sutton and Parmelee 1955 . Down still present on chicks 17 d old; remiges one-third grown. At 22 d, wing-tips stick out, white collar is noticeable, and dark chest-band is indistinct; down is present on feathers on head and throat but not on rectrices; remiges are still sheathed at base at 31 d.

Brooding

Chicks are brooded soon after hatching, but rarely after 5 d of age. Significant negative relationship between time spent brooding during first 5 d and temperature (r = –0.35, p = 0.05, n = 31; Sullivan Blanken and Nol 1998).

After chicks are 3 d old, males and females begin taking turns attending nest much as during incubation, but with the nonattending adult often within vocalizing distance (MSB). Females abandon their mate and brood about 15 d (range 15–25 d, n = 30) after eggs hatch, leaving males as sole guardians (MSB). In Oregon and Washington, south of main breeding range, females and males remain with brood until fledging (Hallet et al. 1995). Adults spend greater amount of time foraging as their chicks get older (Sullivan Blanken and Nol 1998). Males vocalized and flew more frequently than females, leaving chicks unattended, but they also guarded older chicks (Sullivan Blanken and Nol 1998). These flights were in pursuit of an invad-ing species or conspecifics. Other than flying and vocalizing, males and females showed similar behaviors while rearing chicks (Sullivan Blanken and Nol 1998).

Feeding

Chicks find their own food; not fed by parents. Territories always contain some water, and chicks may be led there to feed. Foraging by adults increased significantly as chicks aged (r ²= 0.21, p < 0.05; Sullivan Blanken and Nol 1998).

One report of 1 female caring for 2 broods; female stayed behind after other females left study area, took care of young, and male took care of second brood (female, male, and chicks were banded; G. LaFontaine pers. comm.).

Not reported, and no evidence based on DNA-fingerprinting data (Zharikov 1998).

Departure From Nest

Within 1 d of hatching.

Growth

No data.

Association With Parents Or Other Young

Chicks stay close to parents, although distance from parents to chicks increases as chicks age (distance = 0.43 age (d) + 2.96, r ²= 0.35, p = 0.004, similar at coastal and inland sites; Sullivan Blanken and Nol 1998). Chicks never observed fighting; usually remain distant from each other except when being brooded (MSB). When multiple chicks are brooded, 1 chick often pops out from under parent when another chick enters, especially when brood consists of 4 chicks (MSB).

Ability To Get Around, Feed, And Care For Self

Chicks walk and feed within hours of hatching, but they are brooded frequently (MSB). Except for brooding and protection from predators through vocal warnings from adults, chicks care for themselves (MSB).

Chicks appear to flock together after parents leave; remain on coastal feeding areas.