Breeding

Pair Formation

Begins when birds arrive on breeding sites in early spring; arrival varies from mid-March in Virginia to early May in Manitoba. In densely populated northern sites (e.g. West Shoal Lake, Manitoba), most pairs establish within a day or two of the birds’ arrival (SMH). Pairs on sites with fewer birds take several days or weeks longer to become established. Males on these sites courted a number of females or even flew to another site (32 km away) to court females back to Lake Manitoba (SMH).

Nest Building

See Behavior: sexual behavior. Male begins nest-scraping and stone tossing as part of courtship (i.e. within a few days after arrival in spring). Number of days spent lining the nest varies considerably and seems to depend on strength of the pair bond and weather (SMH). In cold, late springs, nestbuilding may be delayed up to a month past arrival (SMH).

First Brood Per Season

(See Fig. 3). One brood per year. Females may lay several clutches if their nests are destroyed, but still raise only one brood. Most first clutches in Saskatchewan, Manitoba, and Nova Scotia initiated during the first two weeks of May (Cairns 1977, Whyte 1985, SMH); North Dakota birds aweek earlier (Prindiville Gaines and Ryan 1988). Peak hatch usually the first two weeks of June. Chicks tended until fledging 21–35 days later. New York chicks fledge in 30–35 days (Wilcox 1959); Saskatchewan and Nova Scotia chicks in 27 days (Cairns 1982, Whyte 1985); North Dakota chicks in 21–28 days (Prindiville Gaines and Ryan 1988).

Second brood per season . Rare instances of double brooding described for Griswold Point, CT, Assateague Island National Seashore, VA and MD, Wilderness State Park, MI, and Cape Sable Island, NS (Bottitta et al. 1997, J. Stucker and C. Haffner pers. comm., Amirault pers. comm.). Of nine second clutches, the earliest was initiated in Connecticut on 19 June (Bottitta et al. 1997). Most birds were serially monogamous. However, reports of polyandry from Nova Scotia and Manitoba indicate females may abandon the first mate and brood to initiate a second nest with a different male (Amirault pers. comm., SMH). In the Great Lakes a pair initiated a second nest and an unfledged chick from the first brood attended the nest with the parents during incubation (C. Haffner pers. comm.).

Selection Process

See Behavior: sexual behavior. Not clear which parent makes the final choice of nest scrape. Males dig many scrapes during courtship; the one in which most copulations occur becomes the nest. Females may choose the scrape in which they allow the male to copulate (SMH).

Microhabitat/Site Characteristics

Similar nest site requirements for different populations, despite the species’ broad geographic range and use of varied beachlike habitats. Studies from Alberta (Weseloh and Weseloh 1983), Saskatchewan (Whyte 1985, Espie et al. 1996), North Dakota (Prindiville Gaines and Ryan 1988), South Dakota (Schwalbach 1988), Nova Scotia (Cairns 1982), New Jersey (Burger 1987), Massachusetts (Strauss 1990), and Michigan (Powell and Cuthbert 1992) all found nest sites with the following characteristics: open sand, gravel, or shell-covered substrate (generally not bare alkali); within elevated areas; near small clumps of grass but usually not in patches of evenly distributed vegetation; generally near large objects (e.g., stones, logs); and away from water, relative to randomly chosen territories or randomly placed artificial nests. Nests sometimes located on the inland side of foredunes at Great Lake sites (Powell and Cuthbert 1992, Wemmer 2000). Along the Platte River, NE, nest sites were located on river segments characterized by greater channel width and sandbar area relative to random sites (Ziewitz et al. 1992). Although gravel habitat selected in most parts of Nova Scotia and New Brunswick, grassy areas were preferred in southern Nova Scotia perhaps in response to increased nest predation in gravel habitat (Flemming et al. 1992). However, at Lake Diefenbaker, SK, depredated nests were closer to vegetation than successful nests (Espie et al. 1996).

Construction Process

See Behavior: sexual. Nests scraped during daylight hours (no information on night activity). A scrape with pebble lining can be constructed in a day (as with renests), but a new pair in spring usually takes 5-10 days to settle down to one scrape (during which time the nest lining is added as part of courtship). In areas where no pebble/shell lining is added, nest construction takes less than a minute.

Structure And Composition Matter

Nests dug in sandy substrate; may or may not be lined with bits of pebbles and shells. In Great Lakes, zebra mussel (Dreissena polymorpha) shells and crayfish (Decapoda) carapaces are incorporated into nest scrapes where abundant (J. Stucker pers. comm.).

Dimensions

9–10 cm in diameter and 1–2 cm in depth (Whyte 1985).

Microclimate

No specific information except that nests are placed in open areas exposed to harsh weather conditions.

Maintenance Or Reuse Of Nests, Alternate Nests

Adults continue to line nests with pebbles and shells throughout laying and incubation. Nests rarely, if ever, reused. Nest depression is often blown over with sand if not used quickly. Female observed to dig eggs out from under 5cm sand and resume incubation after a severe storm in Great Lakes (J. Stucker pers. comm.).

Nonbreeding Nests

Not known to occur.

Shape

Intermediate between short oval and short pyriform.

Size

See Appendix 1 . Within clutches, Wilcox (1959) reported fourth egg largest but Cairns (1977) disagreed. In Nova Scotia, egg size varies among clutches but not within (Cairns 1977). New York fresh egg weights average 9.8 g (s = 0.44, range = 9.3-10.7, n = 24; Wilcox data reanalyzed by SMH). Cairns (1977) did not report exact egg weights but stated Nova Scotia eggs weighed more than New York eggs. Egg shell thickness and proportional egg weight/female weight not reported.

Color

Pale buff marked with fine splotches of black, brownish black, or purplish black (Cairns 1982). Markings usually evenly distributed, but some eggs have more, larger, and darker spotting at broad end. Within clutches, intensity and size of markings usually similar.

Surface Texture

Smooth and nonglossy to slightly glossy.

Egg Laying

Difficult to determine when nests are complete (relative to laying of first egg) since birds continue to dig and line scrapes. Laying observed throughout daylight hours (Cairns 1977, Whyte 1985). Six days average laying time for first clutches (4 eggs/clutch) in Manitoba (Haig and Oring 1988c), Saskatchewan (Whyte 1985), Nova Scotia (Cairns 1977), and New York (Wilcox 1959). Clutches with longer laying times generally have a longer period between first and second eggs than between subsequent eggs (SMH). Laying slows or stops in early spring if weather becomes inclement (Cairns 1977, J. Stucker pers. comm., SMH).

Replacement eggs not reported. If one or more eggs are lost, pair continues to incubate remaining eggs. One-egg nests deserted in Manitoba but maintained in Great Lakes (J. Stucker and C. Haffner pers. comm., SMH).

Parental behavior during egg laying includes incubation of eggs, copulation until the fourth egg is laid, and intense territory/mate defense if necessary (more frequent if neighboring male does not have a mate). Cairns (1977) observed a female laying an egg shortly after copulating. She remained in nest for 45 minutes before egg was laid, maintained a semi-crouched position, shuffled about, and pecked at breast feathers and the nest scrape until the egg emerged.

Onset Of Broodiness And Incubation In Relation To Laying

Varies considerably. In Manitoba, most first eggs incubated at least during daylight hours, although eggs are left untended for short periods (no night observations conducted). Low spring temperatures may have warranted this incubation to keep eggs from freezing (SMH). Whyte (1985) observed birds incubating one- to two-egg clutches, but Cairns (1977) reported incubation off and on after third egg, full incubation only after fourth. Incubation initiated after third or fourth egg in Great Lakes (J. Stucker pers. comm.).

Incubation Patches

Present in both sexes (L. Oring pers. comm.).

Incubation Period

Mean of 28 days in Saskatchewan (Whyte 1985), Nova Scotia (Cairns 1977), and New York (Wilcox 1959); 25.7 days in Manitoba (Haig and Oring 1988c). Incubation time decreases for nests initiated later in season (J. Stucker pers. comm.).

Parental Behavior

Both sexes incubate, so eggs are usually covered 100% of the time (SMH). In warm weather, eggs are occasionally left exposed for several minutes while the incubating bird walks nearby. At changeover, incubating bird sometimes stands over eggs and performs tilt display while mate walks underneath and sits on the eggs. This exchange is quick and well orchestrated. Bird on recess walks or flies to shoreline or a nearby mudflat to feed. Incubation rhythm varies considerably with weather and stage of incubation, but both sexes appear to share duties equally (SMH). During mid-incubation with mild (15°-25^°C) temperatures, Manitoba birds switch approximately every 30-45 minutes (SMH). In Minnesota, average incubation time was 12.6 min. for males and 16.5 min. for females (Maxson 2000). In Great Lakes incubation normally 60-90 minutes between changes and periodically exceeds 120 minutes; incubation times appear to decrease when food is readily available (J. Stucker and C. Haffner pers. comm.).

Hardiness Of Eggs

Eggs exposed 2 hours - 7 days have been artificially incubated to hatching in Great Lakes; exposure to extreme temperatures (low or high) inhibit successful hatching and survival. Incubation at suboptimal temperatures led to developmental abnormalities and/or lengthened hatching (F. Cuthbert and J. Stucker pers. comm.)

Preliminary Events And Vocalizations

Tiny star-shaped cracks first appear around the broad end of egg up to five days before hatching. Peeping calls heard up to two days before hatching. No distinct hole pipped until six hours before hatching (Cairns 1977). The day hatching begins, parents change incubation roles frequently (every 5 minutes; SMH) and the bird on recess remains close to the nest.

Shell Breaking And Emergence

Nestmates hatch within four to 24 hours of each other (Nova Scotia: Cairns 1977, Saskatchewan: Whyte 1985, Great Lakes: J. Stucker pers. comm.). No relationship found between hatch order and laying order (Cairns 1977). Eggs hatch early morning to late afternoon (SMH). Newly hatched chicks remain in nest several hours while they dry and remaining chicks hatch.

Parental Assistance And Disposal Of Eggshells

Shells removed by incubating bird; picked up in bill and carried (walking or flying) away from nest (up to 40 m) before dropping, often over water (Cairns 1977, SMH). However, in Colorado, very small fragments were usually found in successful nest scrapes of Piping Plovers, Snowy Plovers and Killdeer. Piping Plover sample size was small in this study, however, eggshells were rarely found in depredated nests suggesting their presence may be used as an indirect indicator of nest success (Mabee 1997).

Condition At Hatching

Precocial downy chicks (Fig. 6) are white below with a white collar around entire neck, white around bill, and white manus (Bent 1929, SMH). Upper parts of head and back brownish black speckled with grayish buff and browns. Crown, back, rump, thighs, and upper part of manus outlined in black. Black line from eye to base of head. Black beak, orange legs. Egg tooth generally lost the first day.

Several hours after hatching, chicks can walk a few meters from nest before running back to be brooded (Cairns 1977). They peck at the ground as if foraging, but probably obtain little nourishment for several days (Cairns 1977).

Growth And Development

At one day of age, chicks weigh 6.3-7.2 g with culmen 6.3-7.5 mm; at 10 days, 8.8-16.9 g and 9.2-9.6 mm; at 21 days, 35.6-37.2 and 11.9-12.2 mm (Wilcox 1959, Cairns 1977). Chicks below 60% of adult weight by day 12 are unlikely to survive (Cairns 1977).

Body temperature control enhanced by frequent (every 5-10 min) brooding bouts. Chicks respond immediately to parent alarm calls by lying flat on ground with head down. Cryptic downy plumage makes them exceedingly difficult to see, even at close range. A day or two after hatching, parents and chicks may move away from the nest scrape, although they frequently remain on the same territory unless disturbed. Chicks generally stay close to parents and alternate between feeding and being brooded. Chicks that stray onto foreign territories meet mixed results. Neighboring adults may chase intruding chicks and peck them; sometimes chicks are killed (SMH). Alternatively, when females desert, two males may occasionally tend their chicks together in a combined brood (SMH, D. Amirault pers. comm.). Flemming (1987) reported a neighboring female allowed a stray chick to feed with her brood for 10 minutes before it wandered back to its own brood. Sibling behavior not studied, yet casual observations do not indicate strong intersibling aggression (SMH).

Brooding

Both parents tend broods immediately after hatching, but some females desert broods within 5-17 days (Haig and Oring 1988c, Maxson 2000). Female brood desertion may be less common and later on Atlantic Coast but has occurred as early as 1-2 days post-hatch in the Great Lakes (A. Hecht pers. comm., J. Stucker pers. comm.). When biparental, males and females change brooding duties as with incubation (changing every 30-45 min). Nontending parent forages away from brood while the tending adult broods chicks and forages within several meters of them. Chicks need less brooding as they age; past 21 days, brooding infrequent (Cairns 1977).

Feeding

Chicks forage near parent and immediately use “peck-and-run” foraging behavior of adults. Chicks older than several days may use “foot-trembling” in foraging. Chicks younger than 20 days spend the majority of their time feeding (Loegering and Fraser 1995, Goldin and Regosin 1998). On Lake Superior, in Northern Michigan, chicks consumed terrestrial and aquatic invertebrates from the following orders: Hymenoptera, Coleoptera, Diptera, Hemiptera, Homoptera, and Ephemeroptera (Cuthbert et al. 1999). On Atlantic Coast chicks forage in invertebrate rich bay and pool habitats when available (Loegering and Fraser 1995, Elias et al. 2000). On ocean beaches, terrestrial invertebrates may be more common prey than aquatic invertebrates since chicks prefer feeding in wrack lines (Goldin 1993, Hoopes 1993, Elias et al. 2000) and are seldom seen in the intertidal zone (Loegering and Fraser 1995, Elias et al. 2000).

Parental Carrying

Parents do not carry young.

Not known to occur.

Not known to occur.

Departure From Nest

Several hours after hatching.

Growth

Mass doubles in first two days and quadruples by the seventh day (See Young Birds: growth and development). Weight gain slowed during growth of primary and secondary flight feathers (J. Stucker and F. Cuthbert unpubl. data.). Period from hatching to fledging difficult to determine accurately because chicks flap wings and lift off ground several days before fledging. Sustained flight attained at 27 days in Saskatchewan (Whyte 1985), 21-28 days in North Dakota (Prindiville Gaines and Ryan 1988), 28-32 days in Nova Scotia (Cairns 1982), and 30–35 days in New York (Wilcox 1959).

Association With Parents Or Otheryoung

Family groups (at least male and chicks) maintained through fledging and sometimes until migration south (SMH).

Ability To Get Around, Feed, And Care For Self.

See above: Parental care.

Little research has been done on juveniles, but radio telemetry results from a few North Dakota birds indicate that birds may move ≤ 50 km within a few days of attaining flight (Knetter et al. 2001). Juveniles migrate south in late summer or early fall (see Migration) and return to potential breeding sites the following spring (Haig and Oring 1988b; see Demography and Populations: range).