Breeding

Arrival And Pair Formation

Arrive on northern breeding grounds late May and early Jun with great regularity. Recorded s. Greenland as early as 23 May, reaching north coast by 3–4 Jun, fully populated end of first week of Jun (Manniche 1910, W. E. Ekblaw in Bent 1929, Salomonsen 1950, Korte et al. 1981, Meltofte 1985). Numerous arrival dates north coast Ellesmere I.: Alert, 5 Jun 1876 (Feilden 1877), 2 Jun 1951 (MacDonald 1953); Cape Baird, 2 Jun 1883 (Greely 1888); Fosheim Peninsula, 26 May 1950 (Parmelee and MacDonald 1960), 31 May 1951 (J. Tener in Godfrey 1953), 30 May 1954, and 27 May 1955 (Parmelee and MacDonald 1960); Hazen Camp, regularly early Jun, between 2 and 4 Jun 1963 to 1966 (Savile and Oliver 1964, Nettleship 1973), arriving Tanquary Fiord and Hare Fiord on 29 May and 1 Jun 1966, respectively (Nettleship 1973). Arrival dates south and west similar: Banks I., 29 May 1953 (Manning et al. 1956); se. Victoria I., 3 Jun 1960 and 30 May 1962 (Parmelee et al. 1967); Yukon North Slope, 18 May 1972 (Salter et al. 1980); Colville River delta, 21 May 1984 (North et al. 1984 in Johnson and Herter 1989); earlier w. and n. Alaska, ne. Bering Sea, and Seward Peninsula normally by mid-May, settlement and commencement of egg-laying by third week of May (Thompson 1973, Kessel 1989). Also see Behavior: spacing, above, and Figure 3 .

Dispersal inland soon after arrival, settlement and pairing occurring within 7–10 d, partially regulated by rate of snowmelt on breeding habitat, but usually signs of area attachment well advanced by end of first week of Jun at high-latitude locations: Ellesmere I. and n. Greenland (Parmelee and MacDonald 1960; Nettleship 1967, 1973; Meltofte 1985). Egg-laying normally underway by 10 Jun; earlier in southwest part of North American breeding range.

Nest Selection And Building

Period from arrival through pair formation, courtship to nest-site selection and laying about 10–12 d, usually before mid-Jun. “Dummy” nests first, with final nest-scrape immediately before or during laying.

First/Only Brood Per Season

First egg laid soon after settlement and pair formation, usually within 7–10 d, but can be delayed by late snowmelt and availability of invertebrate foods (Bergman 1946, Nettleship 1967, Meltofte 1985). Timing of first eggs 10–21 Jun in n. Ellesmere, with 46% within 3 d, 13–15 Jun; 62% of clutches (n = 13) completed 19–21 Jun in 1966 (Nettleship 1967, 1973); range similar to dates recorded from s. Ellesmere (Parmelee and MacDonald 1960) southwest to Victoria and Jenny Lind Is. (Parmelee et al. 1967) toward southern limit of breeding in Canadian arctic archipelago and Greenland (Meltofte 1976a, 1976b, 1979, 1985). Farther southwest, first eggs third week of May (Johnson and Herter 1989), as early as 19 May on Seward Peninsula (Kessel 1989). Initiation of laying and clutch completion timed to have eggs hatch at peak of insect emergence: aquatic dipterans, mostly chironomids (see Nettleship 1967, 1973).

Timing Of Breeding: Egg-Laying, Hatching, And Fledging

Figure 3 . Hatching early to mid-Jul; peak variable between years: 4–6 Jul (n = 9) at Fosheim Peninsula, Ellesmere I., in 1955 (Parmelee and MacDonald 1960), and 7–14 Jul (n = 11) farther north at Hazen Camp in 1966 (Nettleship 1967, 1973; Nettleship and Maher 1973). Flying young normally first seen 24–27 Jul at both high and low latitudes (Godfrey 1953; Parmelee and MacDonald 1960; Savile and Oliver 1964; Nettleship 1967, 1973; Parmelee et al. 1967; Nettleship and Maher 1973), with most young fledging last few days of Jul and early Aug. Annual breeding cycle on Greenland appears to be similar (Manniche 1910, Salomonsen 1950, Meltofte 1985).

Second Brood And Replacement Clutches

No records or evidence of >1 clutch in same year except when first clutch destroyed or abandoned early in breeding season. Only verified replacement clutches from southern regions of breeding range including Gulf of Bothnia (Bergman 1946, Vuolanto 1968) and possibly Kandalaksha Bay (Bianki 1967). Interval from loss of first clutch to production of first egg of second about 8 d (Bergman 1946).

Selection Process

After territory established by male and pair formation complete (usually same territory and mate of previous year), pair engages for several days moving about nesting space, exploring, and examining various habitat areas as potential sites, with concentration of effort on certain areas over time including production of ≥1 scrapes by male. Made with several body twistings while calling, female joining male in depression for short time, then female performs several twists after male departs. Several scrapes can be made by male during selection process, but none used by female when laying eggs (Bergman 1946). Ultimately, female selects site and makes scrape at actual time of laying first egg (Bergman 1946, Nettleship 1973). Courtship activities and copulation always associated with site-selection process. Site normally close to nest location of preceding years, but rarely nest depression of previous year (Bergman 1946).

Microhabitat

Little information, but energy expenditure known to be high during incubation, particularly at high latitudes, where prevailing climatic conditions can be harsh (Piersma and Morrison 1994). Research should be directed toward the assessment of features of sites used for nesting in relation to differential en-ergy expenditure and subsequent influence on breeding performance, site fidelity, and survival.

Site Characteristics

In northern parts of range, nests mostly on aven hummocks or tundra habitat, with nest cup scraped into top or edge of patch of aven, sometimes willow (Salix), and occasionally well-vegetated arctic heather grass (Cassiope sp.) slopes (Nettle-ship 1967, 1973), generally low-lying dry tundra, close to wet areas such as streams, ponds, or lakes. Site often protected or partially protected from prevailing winds, also usually orientated to maximize potential exposure to radiant heat (Nettleship 1967, Piersma and Morrison 1994). Tendency for some clumping of nests at locations close to food-rich habitats, normally mesic areas where insect emergence is high (Nettleship 1973, Meltofte 1985). Elsewhere, also from bare gravel or sand-barren habitats, and prostrate vegetation to marine-influenced coastal areas and on gravel bars along rivers near coast (Johnson and Herter 1989, Kessel 1989).

Construction Process; Structure And Composition Matter

Shallow nest scrape formed by body-twisting of female as eggs are laid (Bergman 1946, Nettleship 1973). Depression on or beside mat or clump of vegetation, often aven-capped hummock or willow branch (see also Nest site, above). Brooding female picks leaves from surrounding vegetation, usually aven, some willow and white lichens, to line bottom of nest cup (Parmelee and MacDonald 1960; Nettleship 1967, 1973).

Dimensions

Length, width, and depth of 15 nests at Hazen Camp averaged 11.1 cm (range 10.0–12.0), 10.1 cm (range 8.0–11.5), and 3.1 cm (range 2.5–5.0), respectively; deepest and most heavily lined nest cups were in thick Dryas patches (Nettleship 1967, 1973). Five nests at Hooper Bay, AK, had inside diameters 9.5–11.4 cm and overall depths of 2.5–4.5 cm (H. W. Brant in Bent 1929).

Microclimate

No data, but nest site normally dry and somewhat sheltered, although conditions vary (see Nest site, above). At s. Gulf of Bothnia, temperatures in nest increased from 30° to 31°C during early incubation (days 1–7) to 34°C (day 14) and 38° to 40.6°C in late stages (day 18 onward) of incubation (Bergman 1946).

Maintenance And Reuse Of Nests

Nest of previous year not normally reused, although new site usually in same general area; depressions made by male never used (Bergman 1946). Little maintenance performed. Occasional slight rotation of body at start of incubating bout following changeover, usually either to rearrange eggs or remove unwanted debris (e.g., leaf or twig) from depression. Picking of surrounding vegetation sometimes occurs while incubating, likely done to increase nest-lining or enhance visibility.

Nonbreeding Nests

Scrapes constructed by males common on certain areas within territory, often close to final site selected by female. Male scrapes made prior to initiation of laying are part of courtship and nest-site selection process and precopulatory activity. No “sham” nest depressions receive eggs (Bergman 1946).

Shape, Surface Texture, And Color

Typically ovate to short pyriform, smooth and slightly glossy, with variegated color pattern of dark brown or buff and olive-green, usually irregularly speckled and spotted, tending to have heaviest blotches and streaks at blunt end (Bent 1929, Nettleship 1973, Harrison 1978). Two color forms described by Pleske (1928): common type, with thick, superficial spots almost obscuring ground color, and less common type, where olive-buff ground color predominates. Most of 39 eggs at Hazen Camp, Ellesmere I., were of the common type (Nettleship 1967, 1973); those examined (n = 20) at Fosheim Peninsula, Ellesmere I., varied, mixed within and among 5 4-egg clutches (Parmelee and MacDonald 1960).

Size And Mass

Measurements of length and breadth of 39 fertile eggs at Hazen Camp in 1966 averaged 41.3 mm (range 39.0–45.2) and 28.6 mm (range 29.7–27.8), respectively (Nettleship 1973). Averages similar to those from Fosheim Peninsula in 1955 (Parmelee and MacDonald 1960), Ellesmere I. and Cambridge Bay, Victoria I., and Jenny Lind I., in 1960 (Parmelee et al. 1967). Two major recent samples from high-arctic and low-arctic Canada provide comprehensive measurements (from R. I. G. Morrison unpubl.): Alert/Lake Hazen (Ellesmere I.: interpres; n = 92), averaged 40.3 mm ± 1.78 SD long (range 34.6–45.8) and 28.6 mm ± 0.70 SD in breadth (range 27.1–30.1); Foxe Basin (mostly Rowley I.: morinella; n = 730), averaged 39.9 mm ± 1.42 SD (range 34.9–44.0) long and 28.5 mm ± 0.74 SD in breadth (range 25.4–30.4). Differences in egg dimensions between high- and low-arctic sites statistically insignificant (p > 0.05); averages roughly similar from all samples collected. Large European samples exist for Baltic and White Seas regions (Bianki 1967, Väisänen 1977) and other locations (for details, see Schönwetter 1967, Cramp and Simmons 1983).

Egg mass variable, with few accurate measurements of fresh eggs: calculated mass at laying for Alert/Lake Hazen (Ellesmere I.: interpres; n = 92) and Foxe Basin (mostly Rowley I.: morinella; n = 730), averaged 17.31 g ± 1.14 SD (range 14.93–19.40) and 17.42 g ± 1.21 SD (range 12.12–20.43), respectively (R. I. G. Morrison unpubl.). European calculated mean mass of 17.9 g for interpres (Schönwetter 1967) similar. Thus, mean 4-egg clutch mass about 69.2 g for interpres and 69.7 g for morinella, or roughly 62% of mean body mass of female (means: high-arctic Canada, 111 g; low-arctic Canada, 113 g; see Table 2 for female mass).

Eggshell Thickness

No information.

Clutch Size And Egg-Laying

Typically 4-egg clutch, sometimes 3, rarely 2 or 5 (Manniche 1910, Bent 1929, Parmelee and MacDonald 1960, Parmelee et al. 1967, Nettleship 1973, Meltofte 1985, Kessel 1989). Of 52 clutches in high (Ellesmere I.) and central low (Victoria I.) Arctic: 2 with 2 eggs, 4 with 3 eggs, 46 with 4 eggs, or average 3.9 eggs (Parmelee and MacDonald 1960, Nettleship 1967, 1973; Parmelee et al. 1967). In Greenland and n. Europe, size of 484 clutches averaged 3.9 eggs (Väisänen 1969, 1977). At southern edge of breeding range, Gulf of Bothnia, in 1967, 19 of 24 clutches had 4 eggs (79%), 5 had 3 eggs (21%), or average clutch size of 3.8 (Vuolanto 1968); small samples between 1939 and 1944 totaled 29 clutches, all 4 eggs (Bergman 1946).

High synchrony of egg-laying normal; most variable under inclement weather conditions, particularly late or unseasonal snowmelt (Nettleship 1967, 1973; Meltofte 1985). Most energy for egg production obtained from breeding grounds, only some during migration (R. I. G. Morrison and K. Hobson pers. comm.). Laying interval variable, 3–7 d for 4-egg clutch, but usual production rate 1/d for first 3 eggs, 1–2 d for last of 4-egg clutch (Bergman 1946, Parmelee and MacDonald 1960, Nettleship 1967, Meltofte 1985). Also see Breeding: phenology, above.

Onset Of Broodiness And Incubation In Relation To Laying

Begins after laying of third egg (in 4-egg clutches) until hatching of last egg, partial incubation early (Bergman 1946). By both sexes, but only sporadically by male from laying throughout incubation period to just before hatching in arctic regions (Witherby et al. 1940; Parmelee and MacDonald 1960; Nettleship 1967, 1973). Possibly longer and more regular bouts by male at low latitudes (Gulf of Bothnia), with male mainly mid- to late afternoon and after sunset (Bergman 1946, Skipnes 1979), though no preference recorded at Kandalaksha Bay (Bianki 1967).

Incubation Patches

Two present in both sexes, large and oblong, 1 along each side. Maximum mea-surements (Hazen Camp, Ellesmere I.; DNN): males, mean length 57.8 mm ± 11.5 SD (range 40–75, n = 6) and mean width 11.5 mm ± 4.6 SD (range 13–25, n = 6); single female, 76 × 25 mm. Largest patches recorded late incubation and at time of hatching.

Incubation Period

Twenty-one to 24 d, beginning with third egg of 4-egg clutch (Bergman 1946); normally 22 d in high-arctic Canada (Parmelee and MacDonald 1960, Nettleship 1973).

Parental Behavior

Incubation by both sexes, but usually only sporadically by male (see Incubation, above). Egg-turning and rearrangement common throughout incubation, as is maintenance of nest lining; activity most pronounced immediately following changeover or return to unattended nest. At southern locations (Gulf of Bothnia), both sexes brood regularly, female mainly day and male at night (Bergman 1946); at 1 nest, female 64% and male 36%, with average bouts increasing from 4.7 h early to 16.7 h last 5 d (Skipnes 1979); at Kandalaksha Bay, female bouts twice as long and more diligent than male (Bianki 1967). Qualitative measurements indicate female incubation duties >75% in arctic regions with 24-h daylight during incubation period (Parmelee and MacDonald 1960; Nettleship 1967, 1973; Parmelee et al. 1967). Male attendance and frequency of visitation to nest site increases markedly last week before hatching, though no evidence of increase in actual brooding (Bergman 1946, Parmelee and MacDonald 1960). Interest by male highest immediately prior to appearance of first chick, that by female relatively constant (Bergman 1946). If 1 adult of a pair dies during incubation, surviving bird expected to desert clutch, though 1 female at Fosheim Peninsula (Ellesmere I.) incubated eggs alone for 16 d after her mate died and successfully hatched all 4 eggs, but could not brood chicks, which died soon after hatching (Parmelee and MacDonald 1960). Eggs attended by both parents throughout incubation period, rarely left exposed except when responding to presence of intruder. In southern regions (Gulf of Bothnia, Kandalaksha Bay), eggs left unattended more frequently (Bergman 1946, Bianki 1967).

Hardiness Of Eggs Against Temperature Stress; Effect Of Egg Neglect

Embryonic resistance to chilling likely highest before onset of incubation—similar to Calidrine shorebirds (see Norton 1972)—but survival can remain high if chilling is of short duration (e.g., snow- or freezing-rain storm: Meltofte 1979). Positioning and shape (ovate to short pyriform) of 4 eggs within nest depression likely significant to heat conservation and embryonic survival. Eggs of arctic breeders rarely left unattended during incubation, mainly only when necessary to avoid nest being detected by predators. Physiological adaptations of eggs, chicks, and adults probably extremely high to harsh northern climatic regimes (see Piersma and Morrison 1994).

Generally synchronous, first 3 eggs of a 4 egg clutch hatch out within <24 h, last chick usually next day (Nettleship 1967, 1973); however, 3 4-egg clutches at Fosheim Peninsula (Ellesmere I.) hatched—i.e., time interval from hatch of first to last egg—between <11.0 h and 15.8 h (Parmelee and MacDonald 1960). Typically, nest with 2 newly hatched young and 2 pipped eggs, 1 with 2 distinct holes (Fig. 4: nest 5 at Hazen Camp, Ellesmere I.) at 10:55 on 7 Jul 1966, and 21 h later all 4 young present, a sequence similar for all turnstone nests (Nettleship 1967).

Preliminary Events And Vocalizations

Three to 5 d before hatching, cracks (star pips) appear on blunt end of egg, eventually forming small hole, which indicates egg will hatch within 24 h (Nettleship 1967, 1973). Peeping and tapping of eggshell with egg tooth (on tip upper mandible) by unhatched chick usually evident 2–3 d before hatching, sometimes earlier. Low cheep notes from unhatched chick heard immediately prior to and during egg-pipping, most intense just before emergence from egg; believed to elicit strong brooding responses by adults, particularly male (Bergman 1946; Parmelee and MacDonald 1960; Nettleship 1967, 1973).

Shell-Breaking And Emergence; Parental Assistance And Disposal Of Eggshells

Chick emerges through opening at blunt end of egg, normally without assistance from adult (Parmelee and MacDonald 1960), but sometimes hole enlarged by incubating adult in response to chick’s peeps (Nettleship 1967, 1973). Final egg of a clutch usually last egg to hatch (Parmelee and MacDonald 1960, Nettleship 1967). Once egg hatches, empty eggshell immediately removed by parent and dropped ≥100 m from nest (Nettleship 1973).

Condition At Hatching

Chicks precocial and nidifugous (downy), mobile and walking within hours after hatching, able to peck at objects while looking for insect food. Newly born chicks at Hazen Camp (Ellesmere I.), 8–15 Jul 1966, measured: mean mass 11.42 g ± 0.75 SD (range 10.0–12.5, n = 22), mean exposed culmen 10.36 mm ± 0.51 SD (range 10.0–11.5, n = 25), mean wing 18.52 mm ± 2.00 SD (range 16.0–23.0, n = 25), and mean tarsus 21.92 mm ± 0.76 SD (range 20.0–23.0, n = 25; DNN). Chicks (<24 h old) from other Canadian high-arctic (Fosheim Peninsula, Ellesmere I., 1955: Parmelee and MacDonald 1960) and low-arctic (Cambridge Bay, Victoria I., 1960 and 1962) locations measured: mean mass 10.9 g (range 10.0–12.5, n = 6), mean exposed culmen 10.1 mm (range 9.0–10.5, n = 7), and mean tarsus 20.3 mm (range 19.0–21.5, n = 7; Parmelee et al. 1967). Newly hatched young from variety of locations (mostly European) averaged 90 mm in total length, weighing 11.5–15.0 g (Fjeldså 1977).

See Appearance: hatchlings, below, for description of downy plumage.

Growth And Development

Few measurements of changes in mass from hatching to fledging due to rapid movement away from nest after hatching and difficulty of relocating young. Egg-tooth tip of upper mandible usually disappears first day of life. Fledging period uncertain, probably 19–21 d; chicks of known age fledged by 22–23 d old (Parmelee and MacDonald 1960; Bianki 1967; Nettleship 1967, 1973; Parmelee et al. 1967; Thompson 1973). Gain in mass and size considerable during 19- to 21-d chick-rearing period: mean mass from hatching (about 11.5 g) to recently fledged juveniles (about 93 g at 22–23 d old) equals a mass increase by a factor of 7, roughly 700% over 3 wk, or a mean daily increase of 3.5–3.7 g (DNN). Five recently fledged young—1 known to be 22 d old, others about 21–23 d—measured: mean mass 93.0 g ± 5.8 SD (range 84.1–98.0), mean exposed culmen 21.3 mm ± 0.97 SD (range 20–22.5), mean wing 134.0 ± 2.45 SD (range 131–137), mean tarsus 25.4 mm ± 2.41 (range 22–28), and mean tail 48.7 mm ± 2.47 SD (range 45–51; Parmelee and MacDonald 1960, Parmelee et al. 1967, DNN).

Series of 5 other known-age Ellesmere I. immatures (Parmelee and MacDonald 1960, DNN) likely representative of age cohort and rate of development: <1 d old (mass 10.3 g, culmen 10 mm, wing 17 mm, tarsus 20 mm), 3 d (mass 13.9 g, culmen 11.0 mm, wing 22 mm, tarsus 22 mm), 15 d (mass 56 g, culmen 19.0 mm, wing 101 mm, tarsus 32 mm, tail 22 mm), 18 d (mass 68 g, culmen 19.5 mm, wing 110 mm, tarsus 33 mm, tail 33 mm), 22 d (mass 98 g, culmen 20.0 mm, wing 132 mm, tarsus 34 mm, tail 50.5 mm). Well-developed flying young likely close to adult mass near to departure from breeding grounds (see Fledgling stage, below).

Plumage development rapid. Humeral-feather shafts visible on day 3, split skin on day 4 and emerge as small tufts on day 5; shafts also appear along midline of back and remiges day 6; by day 9, chicks covered all over with feather tufts, small on neck, back, breast, and rectrices, longer on shoulders and wings. At 18 d, primaries and secondaries almost fully developed, at which time chick attempts to fly commence (Bianki 1967). Young fledglings (19–23 d old) often still with natal down on forehead, nape, throat, lower belly, thighs, and round heel of tarsus; those about 5 d older without traces of down (Parmelee and MacDonald 1960, Parmelee et al. 1967, DNN).

Fledgling Flocks

Young tended by both parents, female usually departing mid-fledging period, male remaining until chicks fledge (Nettleship 1973). Juveniles independent at fledging, forming small to large flocks, often mixed with fledglings of other shorebird species, such as Red Knot, and accompanied by ≥1 adult turnstones, almost always males (Parmelee and MacDonald 1960; Nettleship 1967, 1973; Parmelee et al. 1967; Meltofte 1985).

Brooding

Chicks mobile and pecking at objects near nest within hours after hatching. Family group normally deserts nest site within 24 h once last egg hatched. Prior to abandonment, chicks may leave nest for short periods, returning to be brooded by adults. During this period, chicks brooded mainly in nest scrape. After departure, likely brooded regularly for first week by both parents, decreasing substantially during second week. Movement by 1- to 2-d-old young with parents can be rapid (e.g., 400 m in <16 h) en route from nest to distant food-rich areas. Chicks guarded constantly by both parents for first 10–14 d, later mainly by male until young fledge; male aggressiveness and intensity of alarm calls always higher than female (Parmelee and MacDonald 1960; Nettleship 1967, 1973). Single parent unable to brood 4 young successfully prior to onset of thermoregulation (Parmelee and MacDonald 1960). Little detailed information available on chick-adult behaviors after family group departs nest site.

Feeding And Food Of The Young

Young self-feeding. Parents guard rigorously, leading chicks to food-rich habitats—usually wet areas where recently emerged small and soft-bodied dipteran insects, mostly chironomids, occur at high densities. Family movements over tundra coordinated mostly by male parent in relationship to timing of insect emergence and availability of food for the young. Chicks not fed by parents, although adult foraging behavior likely important to identification of prey (Nettleship 1967, 1973; DNN). Also see Food habits, above.

Nest Sanitation

Adults and chicks desert nest scrape within 24 h after last egg of clutch hatched. Eggshell removed from nest by 1 parent immediately after each chick emerges and dropped a considerable distance away (Nettleship 1967, 1973).

Not known to occur.

Not known to occur as a reproductive strategy. Five-egg clutches—recorded rarely (e.g., Witherby et al. 1940, Väisänen 1969, Bianka 1977, Harrison 1978)—believed to be laid by single female.

Departure From The Nest, Association With Parents Or Other Young

Chicks directed away from nest scrape by parents within a day after last egg hatched. Family group remains together, moving on foot from nesting area to locations where food suitable for chicks is most abundant. Concentrations of individual family groups often occur at these food-rich locations—slopes or beds of marshy areas and edges of ponds—leaving territories vigorously defended only a few days earlier vacant. Aggregations of adults and young sometimes include families of other species, especially Red Knot in northern regions. Parental guarding of young shared by sexes; adult females leave family group first, usually midway (7–10 d) through fledging period; males only once young fledge (Parmelee and MacDonald 1960; Nettleship 1967, 1973; Parmelee et al. 1967; Meltofte 1985). See Hatching, Young birds, and Parental care, above.

Age And Condition At Departure

First flight at about 19 d of age (range 19–21), at which time female parent has already departed, and bond between male parent and young dissolves.

Growth

Well-developed flying young (21–23 d old) depart breeding grounds close to adult size (sexes combined): about 83% adult mass, 91% adult wing length, 100% adult exposed culmen, 100% adult tarsus length, and 78% adult tail length (Parmelee and MacDonald 1960, Parmelee et al. 1967, DNN).

Poorly known. Normally remain with postbreeding group into fall, but details from postbreeding dispersal to wintering quarters uncertain. Survival rates of immatures from fledging to first breeding at age 2 yr unknown. See Fledgling stage, above.