Breeding

Phenology

Pair Formation

At Sable I., Nova Scotia, males precede females to breeding grounds (median = 7 d earlier), with breeders arriving there in flocks of up to 8 birds (Miller 1983a). In northern areas, breeders sometimes arrive suddenly in large numbers (Yarbrough 1970). Pair formation for reunited pairs from previous years takes place rapidly, with nesting beginning shortly after pairing (Jehl 1970).

On Sable I. in mid-May, 30% of adults present as pairs; percentage rises into late May (Miller 1983a). Most pairs reform in subsequent years if both members of pair return to breeding area (Cooper 1993). At Queen Charlotte Is., males begin aerial displays by the first week of May, and early pair formation begins at same time. Early breeders probably arrive in late Apr, and breeders continue to arrive through May (Cooper and Miller 1997). In Manitoba, intersexual size differences may affect efficiency of pair formation in new pairs; large females and small males, as well as pairs with large intra-pair size differences, nest earlier (Jehl 1970). A larger sample on Queen Charlotte I., British Columbia, found no correlations between size or size differences and timing of nesting (Cooper 1993).

On Sable I., 7 of 8 banded males and 3 of 3 banded females that took new mates nested later than during the previous year, but 3 reformed pairs nested no later (Miller 1983a). On Queen Charlotte I., reformed pairs laid first eggs 4.5 d earlier than new pairs (Cooper 1993).

Warm springs promote earlier breeding, a widespread trend in northern scolopacids (Miller 1983a). Although mean average spring temperatures did not differ significantly on Queen Charlotte I., median egg-laying dates varied by as much as 8 d between years (Cooper 1993).

Nest-Building

Several nest scrapes made by male prior to egg-laying.

First/Only Brood Per Season

Figure 6. First egg date on Queen Charlotte I. 11–15 May over 5 yr in 1980s, median 23 May, range 18-26 May (Cooper and Miller 1997); 5 Jun on Magdalen I. (Moore 1912). Three peaks of clutch completion noted on Queen Charlotte I. and Sable I.: first peak, representing early experienced breeders, in first 6–10 d after first clutch completed; second peak, representing late experienced breeders and replacement clutches, 15–22 d after first clutch completion; third peak, representing juvenile breeders and replacement clutches, during last week of clutch completion (Miller 1983a, Cooper 1993). Peak hatch on Queen Charlotte I. in last 10 d of Jun (Cooper 1993). Late clutches hatch in early Jul. Some late clutches abandoned (Cooper 1993). Chicks fledge from late Jun through early Aug, at 14–20 d of age (Miller 1985, Cooper 1993).

Second Brood Per Season

Not known to lay 2 clutches in a season except for replacements of lost clutches (Miller 1983a, Cooper 1993). Replacement clutches laid routinely during early to middle parts of egg-laying period in southern parts of breeding range (Miller 1983a, Cooper 1993). On Queen Charlotte I., replacement clutches initiated a mean 5.5 ± 1.93 d (SD) after loss of first clutches, and as late as 15 Jun (Cooper 1993). Time available for replacement clutches to be laid is significantly less in more northern breeding areas.

Endocrinology

Male testes at maximum size and female ova about 2 mm when individuals arrive on breeding grounds. Gonadal recession virtually complete before fall migration (Yarbrough 1970). In May, Alaska migrants carry more fat than early Jun arrivals in Churchill, Manitoba (Cramp and Simmons 1983). Gonadal recession correlated with lipid increase, after young hatch. Lipid levels decline during late incubation and early nestling period, particularly for males. Fats comprised between 17.4 and 39.7% dry weight of breeding males, between 17.7 and 50.8% of breeding females from early Jun to late Jul, and 21.8% of immatures in late Jul (Yarbrough 1970).

Nest Site

Selection

Males establish nesting area and build scrapes (Miller 1977, 1979b, 1983a, 1985). Females select scrape used for nesting.

Microhabitat

Nests placed in tufts of short marsh grass on damp ground near water (Moore 1912, Jehl and Smith 1970, Miller 1983a, Cooper 1993), usually in or near a small irregularity in vegetation or terrain such as small patches of vegetation lusher than surrounding habitat (Miller 1985). In very wet areas, placed on slightly drier rise or hummock, in a tuft of sedge or mound of Sphagnum moss with sparse sedge (JMC). Conservative microhabitat selection across range thought to be related to need for cryptic cover for nests and proximity of richer, moister feeding areas for chicks (Miller 1983a).

Site Characteristics

Usually damp bogs, muskeg, or sedge meadows throughout range, but also in drier uplands near mudflats or pools of fresh water (Philipp 1925, Townsend 1927, Yarbrough 1970, Miller 1983a, Cooper 1993). On Queen Charlotte I., usually builds in damp open areas away from extensive growths of Juncus effusus, at higher densities in wetter rather than drier habitat, but near water (Cooper 1993). Exceptions to general preference are very open habitats such as sparsely vegetated sand dunes (Miller 1983a) or golf course fairways (JMC).

Nest

Construction

Male constructs nest by pressing body into ground vegetation and making a hollow (Miller 1977). Female perfects cup and adds sparse lining during egg-laying and early incubation.

Structure And Composition Matter

Nest is simple depression in ground cover, usually lined with bits of dead vegetation available in vicinity of nest (Fig. 7) (Miller 1983a, JMC). Nests on Sable I., Nova Scotia, and Magdalen I., Quebec, lined mainly with dead bayberry (Myrica pensylvanica) leaves (Moore 1912, Miller 1983a) or strips of eelgrass (Zostera marina) (Moore 1912).

Dimensions

Inside diameter about 6 cm, depth about 4–5 cm.

Microclimate

No data available.

Maintenance Or Reuse Of Nests, Alternate Nests

Nest-lining material added haphazardly during incubation. Nests not reused between years on Queen Charlotte I. (JMC) but may occasionally be reused in tundra areas, not necessarily by same birds (C. Gratto-Trevor pers. comm.). Prior to pairing, male constructs several potential nestcups (Miller 1977, JMC).

Eggs

Shape

Ovate pyriform, following widespread trend in scolopacids; shape maximizes surface contact and minimizes heat loss in 4-egg clutches.

Size

Magdalen I., Quebec: n = 25, length 29.5 mm, breadth 21.8 mm, calculated volume (length x breadth2) 14.02 mm3; n. Manitoba: n = 88, length 28.6 ± 0.12 mm, breadth 20.5 ± 0.09 mm, calculated volume 12.02 mm3; Sable I.: n = 209, length 29.1 ± 0.03 mm, breadth 21.2 ± 0.06 mm, calculated volume 13.08 mm3; Queen Charlotte I.: n = 1,131, length 28.5 ± 0.93 mm, breadth 20.7 ± 0.45 mm, calculated volume 12.2 mm3 (Philipp 1925, Jehl and Smith 1970, Miller 1979a, Cooper 1993). Eggs from Sable I. larger than eggs from n. Manitoba but smaller than eggs from Magdalen I. (Miller 1979a). Eggs from Queen Charlotte I. smaller than those from Sable and Magdalen I., but mid-range between 2 samples from n. Manitoba (Jehl and Smith 1970, Ricklefs 1984, Cooper 1993).

Egg length and breadth not significantly correlated, but length more variable. Strong individual variation among females in egg dimensions, but size and shape uniform within clutches (Norton 1972, Ricklefs 1984, Miller 1979a). Egg size on Sable I. positively correlated with female culmen length, but not on Queen Charlotte I., where correlated with female mass (Cooper 1993). Third and fourth eggs longer (0.5 mm) than first and second eggs of a clutch. Egg size constant for individual females between first and replacement clutches and between years (Miller 1979a, Cooper 1993). A single case of 1 runt egg in about 300 clutches on Queen Charlotte I. (JMC).

Egg volumes did not differ between replacement and initial clutches (Miller 1979a, Cooper 1993).

Mass

No data available.

Color

Two main pattern types, blotched or spotted (JMC). Dark pigment patterns vary greatly in shape (Moore 1912). Pale buff, spotted or blotched with various browns (Godfrey 1986).

Surface Texture

Smooth and glossy (Harrison 1978).

Eggshell Thickness

In eggs collected from 1932 to 1945 in n. Manitoba, mean eggshell thickness index ±SE = 0.45 ± 0.005 mm (44 eggs from 12 clutches), and from 1948 to 1953, 0.44 ± 0.003 mm (43 eggs from 12 clutches): no significant difference (Morrison and Kiff 1979).

Egg-Laying

Can begin as early as 5 d after initial association between a pair (Miller 1979a). All clutches laid on Sable I. completed over 29 and 33 d in 2 yr (Miller 1983a).

Most egg-laying during morning hours (Philipp 1925, Miller 1983a). Laying intervals in n. Manitoba thought to be 24 h (Jehl 1973), but on Sable I. mean laying interval (n = 17) estimated as 29.6 h (Miller 1983a). Extremes: 62 h for first 2 eggs of a replacement clutch (Miller 1983a); and 72 h, possibly caused by cold-weather-induced food shortage (Jehl 1973).

Only 1 case of egg-dumping found in 6 yr and 300 clutches on Queen Charlotte I., a clutch of 7 eggs, 2 of which were noticeably different in pigment pattern from other 5, so at least 2 females thought to have been involved (JMC).

Replacement clutches routinely laid on Queen Charlotte I. during early to middle portions of breeding season, average 5.5 d after loss of first clutch (Cooper 1993). On Sable I., briefest interval between loss and replacement of a complete clutch was 7 d (Miller 1983a). Data on replacement clutches lacking from northern breeding areas. Eggs lost within a clutch never replaced (Cooper 1993).

No data on calcium requirements, but likely requires supplemental sources as in other Calidris (MacLean 1974, Miller 1983a).

Incubation

Onset Of Broodiness And Incubation In Relation To Laying

Time spent incubating (birds on nests with partial clutches may not be “incubating”) clutches increases gradually from 1-egg to definitive (usually 4-egg) clutches (1 egg–27.3%, 2 eggs–40.4%, 3 eggs–60.7%, 4 eggs–98.7%; Miller 1983a, 1985), a trend typical of northern breeding calidridines (Norton 1972).

Incubation Patches

Incubating males and females have 2 large oblong incubation patches, 1 on each side of midline. Patches develop as nesting begins and regress as young near fledging (Yarbrough 1970).

Incubation Period

In n. Manitoba 20.5 d, range 19.5–23 d (Jehl and Hussell 1966, Jehl and Smith 1970). On Sable I., estimated mean incubation period 20.4 d, range 19.5–21.5 d (Miller 1983a).

Parental Behavior

Incubation shared between sexes, but males incubate for increasingly longer periods as incubation and season progress (Yarbrough 1970, Miller 1985, Cooper 1993). Females tend to incubate at night and in early morning, males from midmorning to dusk (Yarbrough 1970, Jehl 1971, Miller 1985, Cooper 1993). One incubation shift/day for each sex. In late-season clutches, where females have abandoned nest, males leave eggs for several hours to feed (Cooper 1993). Males incubating alone 1–4 d at end of incubation period are able to hatch eggs (Miller 1985, Cooper 1993).

Birds settle on eggs by stepping on to eggs, then settling feet into spaces between eggs. Eggs turned by bill movements (Moore 1912).

Incubating adults rarely abandon nests when disturbed repeatedly by observers, although 1 pair deserted a definitive clutch after discovery (Miller 1983a).

Hardiness Of Eggs

Few data available. One clutch, abandoned by female on Queen Charlotte I. and thought to be twice abandoned because eggs were cold to touch, eventually hatched (Cooper 1993). Male probably left nest for several hours to feed.

Hatching

High fertility. On Sable I., 93% of eggs hatched in clutches that survived to hatch (Miller 1983a); on Queen Charlotte I., 86% of eggs in successful clutches hatched (Cooper 1993); 57% of clutches (n=353) hatched (Cooper and Miller 1997). Failure of clutches is almost always result of predation (Cooper 1993). No difference in hatching success between early and late clutches (Jehl 1970, Miller 1983a, Cooper 1993). Parents occasionally abandon late-hatching egg (JMC). Hatching periods 14–17 d in n. Manitoba (Jehl 1970), 4–5 wk on Sable and Queen Charlotte I. (Miller 1983a, Cooper 1993). Hatching in Manitoba correlated with high food (emerging insect) density and easy accessibility (Jehl 1970).

Preliminary Events And Vocalizations

Adults increase attentiveness as eggs pip, and remain closer to nest when disturbed by humans. Chicks can be heard scraping shell with egg tooth and peeping within egg 1–2 d before hatching (JMC).

Shell-Breaking And Emergence

All eggs in a clutch hatch within 1 d, most within 12 h (Moore 1912, Jehl 1970, Miller 1983a, JMC). Eggs hatch during all hours of day or night (Moore 1912). Last laid eggs hatched last in 2 clutches, a general trend in waders (Miller 1979a). Eggs hatch 2–3 d after first “starring” of eggshell. As in other calidridines, chicks emerge quickly after eggs are “hole-pipped” (Gratto-Trevor 1992, Parmelee 1992).

Parental Assistance And Disposal Of Eggshells

Parents remove shell shortly after hatching (Moore 1912, JMC) by carrying it off in bills and dropping it well away from nest (JMC).

Young Birds

Condition At Hatching

Young precocial and downy when hatched. Down dries and chicks mobile within hours of hatching. Mass of neonates from n. Manitoba, < 6 h old, averaged 4.06 ± 0.31 g (n = 16; Ricklefs 1984).

Egg teeth occur on upper and lower mandible. Thin lower egg tooth lost within a few hours of hatching, thicker upper egg tooth usually within 8–12 h (Jehl 1968a).

Growth And Development

Few data available. Chicks leave nest within 24 h of hatching (Miller 1977), crouch when parents call in alarm, and remain crouched when picked up by human observers (Miller 1985). Crouching response declines with age; when pursued, older chicks run, usually lifting wings as they are captured (Moore 1912, JMC). Brooded by parents during rainy and cold weather while downy (Miller 1985, JMC). When capable of flight, chicks were often prompted to fly, as an observer moved close, by parents swooping at them or landing beside them and flying up suddenly (Miller 1985).

On Sable I., chicks could fly strongly by 14–16 d of age but were attended by parents for a few days longer (Miller 1985). On Queen Charlotte I., males from early-hatching clutches attended broods up to 7 d after chicks could fly (Cooper 1993).

Parental Care

Parental care of hatched chicks limited to brooding, warning of danger from potential predators, and leading chicks to appropriate habitat (Miller 1985). Parents remain together to tend broods except for 2 of 103 broods on Queen Charlotte I. where broods split and were tended by 1 parent in different brood-rearing areas (JMC).

Brooding

Chicks brooded by both parents, if present, or by male alone if female has abandoned brood; brooding begins immediately after hatching and continues for several days (Miller 1983a, 1985, Cooper 1993). Adults may remain on nest to brood remaining chick or egg while young chicks venture away briefly (Miller 1983a). Weak chicks may be brooded in nest for a few hours, and other chicks retained in area, even if stronger chicks want to leave (Miller 1983a). Brooding of chicks out of nest occurs in rain, after disturbance by human observers, and presumably at night (Cooper 1993).

Feeding

Chicks are not fed by parents; feed independently, apparently beginning shortly after leaving nest, on small terrestrial insects taken from moist vegetated habitat (Jehl 1970, Miller 1977, Cooper 1993). Parents lead broods from nest site to brood-rearing areas, with presumably good foraging habitat, immediately after chicks leave nest (Miller 1985, JMC). Broods generally remain sedentary after arrival at brood-rearing areas, although some broods may travel between different brood-rearing areas (200–300 m) 2–3 times before fledging (Miller 1985, JMC). After fledging, chicks venture out onto more open muddy areas to probe for benthic prey (JMC).

Nest Sanitation

Eggshells removed shortly after hatching; rarely found in nests with newly hatched young. Parents fly from nest with shells in bill; drop them > 30 m from nest (JMC). Cracked eggs removed by adults, shortly after breakage. One male carried off a cracked egg in his beak, dropped it 15 m from nest, and was thought to have removed 2 additional cracked eggs within a day (Miller 1983a). Clutches with badly broken eggs that foul nests are invariably abandoned, although 1 nest with 3 crushed eggs was not abandoned after all traces of crushed eggs were removed (Miller 1983a).

Parental Carrying Of Young

Never observed.

Defense Of Broods

Brood-rearing areas are not defended from other adults, but foreign adults close to young chicks are occasionally rushed by a parent (Miller 1985). Miller (1985) reports 1 case of an adult repeatedly attacking a 6-d-old chick and being attacked repeatedly in turn by chick’s father. Aerial chases and fighting on ground were observed between 2 pairs involved in a “brood-napping” event (Cooper and Miller 1992; see Cooperative Breeding, below). Upon approach of a human observer, parents with young chicks fly about, calling loudly, occasionally hovering over chicks as Wilson’s Phalaropes (Phalaropus tricolor) do (Miller 1985); as chicks become older and more dispersed, parents follow observers, calling continuously. Parental care of chicks strongly influenced by chick behavioral maturity rather than simply chick age (Miller 1985), although early-nesting males tend to show protective parental behavior for several days after chicks fledge (Cooper 1993).

Duration Of Parental Care

Males tend broods for longer periods than females and are generally more vigorous in intensity of chick defense. Males tended broods for mean of 20 ± 0.9 d on Sable I. and 17.5 ± 5.2 d on Queen Charlotte I.; females tended broods 6 ± 1.31 d on Sable I., 7.9 ± 4.9 d on Queen Charlotte I. (Miller 1985, Cooper 1993). Duration of parental care declines as season progresses (Miller 1985, Cooper 1993). Although it is normal for 1 adult to tend chicks until they fledge (Yarbrough 1970, Miller 1985), broods hatched on Queen Charlotte I. in early Jul were abandoned by both parents several days before they fledged (Cooper 1993).

Cooperative Breeding

Brood amalgamation or adoption of foreign chicks occurs occasionally in brood-rearing areas at high-density breeding sites. Six cases of brood amalgamation noted on Queen Charlotte I., including mixed broods of 3–5 chicks from 2 or 3 different pairs, brooded or defended by 1 pair (Cooper and Miller 1992). One pair, which had lost 2 clutches to predators, aggressively took possession of a brood of 4-d-old chicks that wandered through their nesting territory, by driving away chicks’ parents. Fledging success of adopted chicks was similar to that of other chicks. Brood amalgamation occurs because of lack of individual recognition of chicks by parents, synchronous breeding, and mixing of broods in undefended brood-rearing habitat (Cooper and Miller 1992).

Brood Parasitism

See Demography and Populations: clutch size.

Fledgling Stage

Period From Hatching To Departure

Chicks usually leave nest within 1 d of hatching, although amount of time depends on time of day chick hatches (Miller 1983a). First-hatched chicks leave 20–30 h after hatching, late-hatching chicks may be only a few hours old.

Departure From Nest

When chicks are 12–24 h old, a parent may walk off nest about 0.5 m and call to them. Chicks leave nest, walk to parent, and are immediately brooded. Brood then led away by sequences of adult walking off a short distance, calling chicks to it, brooding, then walking off again (Miller 1983a).

Condition Of Development At Departure

Chicks mobile within a few hours of hatching (Miller 1983a, Cooper 1993). Older chicks stronger and more mobile than later-hatching chicks (Miller 1983a).

Thermoregulation

Wind is significant factor in thermoregulation of chicks. Thermal conductance of 1–3 - wk-old downy chicks increased by 30–50% as wind speed increased from 0.1 to 3ms–1 (Bakken et al. 2002).

Manner Of Departure: Time Of Day, Behavior Of Chicks And Parents

Prior to leaving nest permanently, chicks venture out for several short (20-min) sorties. Older chicks walk out together but return individually (Miller 1983a). Chicks hatched late in day usually leave permanently in early to mid-morning next day (Miller 1983a). Broods are led from nest within 1 d of hatching and taken to brood-rearing areas (Miller 1977).

Association With Parents Or Other Young

Broods likely break up as chicks near fledging stage (JMC). Early-breeding parents remain in brood-rearing areas and attend chicks until they fledge, males for a few days afterward to a maximum of 22–23 d (Miller 1985, Cooper 1993). Parental attendance declines later in season (Miller 1985, Cooper 1993; also see above, Duration of parental care). On Sable I., fledglings aged 17–20 d remained very close to where they were reared, and only fledglings > 4 wk old were found regularly far (up to several km) from those areas. One chick remained sedentary for 8 wk (Miller 1985).

Ability To Get Around, Feed, And Care For Self

Chicks mobile and feed independently within 1 d of hatching (Miller 1977, Cooper 1993) but require considerable brooding during first few days, particularly during rainy and cold weather (Miller 1977, 1985, JMC).

Mortality

Prefledgling mortality of chicks averaged about 60% (n = 109 chicks) on Sable I. (Miller 1983a). On Queen Charlotte I., 24% of 103 broods suffered 100% mortality, with remainder producing at least 1 fledgling (Cooper 1993). Most broods lost during first wk (Miller 1983a, JMC). Survival of chicks to fledging was “contagious,” so that if 1 chick fledged, others from that brood also tended to fledge (Miller 1983a).

Fledging Success

Although Jehl (1970) felt early clutches fledged more young than later clutches, Miller (1983a) and Cooper (1993) found no seasonal differences. On Queen Charlotte I., 66.8% of 274 chicks that left nest fledged (Cooper 1993).

Immature Stage

Few data. Immatures migrate later than adults (see Migration: Timing and routes of migration, and Control and physiology). Some yearlings remain on wintering grounds and do not breed.

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