Demography and Populations

Age At First Breeding

Age at first breeding normally 2 yr (Bergman 1946, Thompson 1973, Johnson 1979); some possibly 3–4 yr (Bianki 1967). After fledging, migrate to wintering grounds, where yearlings usually remain for their first complete summer, sometimes moving northward, though short of breeding range. Based on banding studies and observations of reproductive condition of Ruddy Turnstones not migrating to northern breeding areas, partial development of breeding plumage in yearlings common, sometimes complete, but reproductive organs inactive (Johnson 1973, 1977, 1979; Thompson 1973; Ens et al. 1990). No information on differences between sexes.

Intervals Between Breeding

Normally each year after sexual maturity and first breeding (Bergman 1946, Bianki 1967). Age-related differences unknown; likely some young males hold territories without breeding and young females occasionally fail to produce eggs due to poor food supply during egg formation; small clutch sizes (<4 eggs) may also indicate young females.

Clutch

See Breeding: eggs, above.

Annual And Lifetime Reproductive Success

Information on annual productivity and breeding success very limited. High- and low-arctic Canada: Ellesmere I. (Fosheim Peninsula, about 79°N, 1955: Parmelee and MacDonald 1960; Hazen Camp, 81°N, 1966: Nettleship 1967, 1973): hatching success, 60.7% (n = 19) and 67.3% (n = 15), respectively; fledging success (percentage of chicks hatched that fledge), no detailed information, but estimated between 40 and 50% at Hazen Camp in 1966; breeding success (i.e., fraction of eggs laid producing fledglings) estimated at Hazen Camp (1966) to be about 30.6% (Nettleship 1967, 1973); overall nest survival (fraction of clutches producing ≥1 chick), 78.6%; egg and chick loss due largely to predation by Long-tailed Jaegers, some to arctic foxes (Parmelee and MacDonald 1960; Nettleship 1967, 1973). Green-land: few data available—in 1975 at Danmarks Havn (about 76°N), 7 nests containing 25 eggs produced 14 chicks (hatching success 56%), with most egg losses due to unusually poor weather conditions during incubation (Meltofte 1979).

At southern limits of breeding range in Europe: Gulf of Finland (about 60°N: Bergman 1946), Gulf of Bothnia (about 63°N: Vuolanto 1968), and Kandalaksha Bay (about 66°N: Bianki 1967), hatching success 72.3%, 52.7%, and 81%, respectively; fledging success 81.5%, unmeasured, and estimated at about 70%; breeding success 58.9%, unknown, and estimated at 57.3%.

No data on lifetime reproductive success. See Table 1 for details on annual breeding performance.

Number Of Broods Normally Reared Per Season

One.

Proportion Of Total Females That Rear At Least One Brood To Nest-Leaving Or Independence

No information.

Factors Affecting Breeding Success

Few serious predators on breeding grounds. See Behavior, predation, above. Major losses of eggs due to embryonic mortality from unusually severe weather conditions, hatching deaths, and accidental damage to eggshell during incubation (Parmelee and MacDonald 1960; Bianki 1967; Nettleship 1967, 1973; Parmelee et al. 1967; Meltofte 1979); some losses by flooding and washing of nests, mostly in southern parts of breeding range (e.g., Bianki 1967). Chicks vulnerable to chilling prior to onset of thermoregulation, less so to aerial and ground predators before fledging. Also see, Conservation and management: effects of human activity, below.

Few data for North American birds. Annual adult survival (based on returns of Ruddy Turnstones banded as breeders): 77.8% in Gulf of Finland (Bergman 1946) and 66.4% ± 3.95 SD (n = 27) in Fenno-Scandia (Boyd 1962); higher in the Firth of Clyde (Scotland): at least 85% based on return rate of individually marked adult turnstones to winter area (Metcalfe and Furness 1985). First-year survival estimated to be 45–58% (Boyd 1962). Average longevity for Gulf of Finland population estimated to be 6–7 yr (Bergman 1946). Maximum recorded longevity 19.7 yr (Rydzewski 1978); 1 of 16,152 Ruddy Turnstones banded at St. George I. (Pribilofs, AK) in fall 1964 and recaptured in spring 1971 near Tokyo, Japan, gives a minimum age of 9 yr (Thompson 1973). No population model has yet been constructed for either North American or European birds.

Diseases

Limited information. No botulism observed in thousands of birds examined on Pribilof Is. (Thompson 1973), though type C known to sometimes adversely affect turnstones and other shorebirds eating maggots from decaying animal carcasses (Austin and Austin 1931, Friend and Laitman 1987). Haematozoa absent in turnstones breeding in the Taimyr Peninsula, Russia (Earle and Underhill 1993).

Body Parasites

Generally, birds considered relatively clean with few ecto- or endoparasites; small numbers of nematode (Nematoda) worms in individuals examined in Iceland (Anderson and Wong 1992).

Few data on causes of juvenile and adult mortality. Fledglings particularly vulnerable to aerial predators before and during departure from breeding grounds. See also Behavior: predation and Measures of breeding activity, above.

Natal Philopatry

Few data. Return rate to natal area appears low for both sexes; of 64 chicks banded in Gulf of Finland, only 1 known to return to natal area (Bergman 1946). Birds likely return to general region of birth, dispersing widely.

Fidelity To Breeding Site And Winter Home Range

High fidelity shown by both sexes to breeding site (territory) after nesting there at least once previously (determined by banded individuals; Bergman 1946, Bianki 1967, R. I. G. Morrison pers. comm.). Although pairs return to same nesting territory and mate, rarely use same nest scrape as previous year (Bergman 1946, Bianki 1967). Generally use same routes and staging areas during migration and wintering grounds year after year (Bianki 1967, Thompson 1973, Branson et al. 1978, Morrison 1984, Metcalfe and Furness 1985, Ens et al. 1990, Gudmundsson 1993, Gudmundsson and Gardarsson 1993). Size of wintering populations at specific locations likely highly stable from year to year, with majority of birds (95%) returning to the same location each fall, where they remain until Apr or May the following year (Metcalfe and Furness 1985).

Dispersal From Breeding Site Or Family Group

Information of dispersal distances after breeding by North American birds is limited. Small number of recoveries indicate distances traveled are considerable by both adults and immatures. For birds breeding in e. Siberia and St. Lawrence I., AK, apparent wintering area lies in Marshall Is. and adjacent islands—more than 4,500 km, with some birds continuing as far as Australia (Sydney), about 10,500 km from St. George I., AK (Thompson 1973, Kessel 1989). Dispersal of central and eastern arctic populations similar, south to n.-central Brazil (9,000–11,000 km), Uruguay, and s. Peru (>9,500 km); high-arctic Canada population dispersing mainly to United Kingdom (via Iceland) and Netherlands to n. Norway, all one-way distances exceeding 6,000 km (Parmelee and MacDonald 1960; Nettleship 1967 b; Morrison 1975, 1984; Morrison and Ross 1989, Smit and Piersma 1989, Rose and Scott 1997). See also Migration: timing and routes of migration, above.

Home Range

On breeding grounds, over large general area encompassing many individual nesting territories at arrival while still in flocks; reduced quickly to area of actual nesting territory once territorial defense and pair formation begins through egg-laying and incubation period; widespread after the hatch when family groups desert their nesting territories for communal feeding areas where food is more abundant (Parmelee and MacDonald 1960; Nettleship 1967, 1973; Parmelee et al. 1967; Meltofte 1985). See Spacing: territoriality, above, for details during breeding.

Numbers And Count Estimates

Best current (1999) estimate of breeding population in North America totals 267,000 Ruddy Turnstones, comprising 235,000 mainly in n. Canada (>95%, remainder in Alaska) and 32,000 in Greenland (Morrison et al. 1999, Meltofte 1985). Totals for races morinella and interpres are 200,000 and 67,000 (35,000 high-arctic Canada; 32,000 Greenland) individual breeding birds, respectively. North American total (267,000) represents almost 60% of the most accurate global total for the species — 449,000 breeding birds (Rose and Scott 1997). Estimates of world population by van Gils and Wiersma (1996) based on counts of wintering birds produced range of 259,000–544,000 birds, though estimate for North American population of 30,000–100,000 most certainly a gross underestimate. Species not globally threatened, and North American populations considered relatively stable (Morrison et al. 1994a, 1994b; van Gils and Wiersma 1996), but data for species relatively weak and many regional populations known to be at considerable risk from human activities adversely affecting critical staging and winter habitats (Howe et al. 1989; also see Conservation and management: effects of human activity, below).

Recent counts in North America of race morinella during spring migration total 160,300 birds, with 87% moving along Atlantic Coast, 13% through central flyway, and <1% on Pacific Coast (Skagen et al. 1998, Morrison et al. 1999). Although count total falls below estimate of total size of North American population (see above: 200,000 breeding birds), proportions of population using the 3 principal migratory routes seem accurate (Morrison et al. 1999). Counts during fall migration and on wintering grounds considerably lower, underlining more diffuse patterns of migratory movement in autumn and winter distribution recorded for both races (Wilson 1981, Meltofte 1985, Gudmundsson and Gardarsson 1993, Morrison et al. 1999).

Trends

Few statistically meaningful data sets available for trend analysis of North American population. However, hunting pressures on coastal shorebirds throughout 1800s and early 1900s, during migration and on wintering grounds in South America, almost extirpated certain species and caused steady declines in most others, including North American morinella race of Ruddy Turnstone (Forbush 1912, Hewitt 1921, Taverner 1922, Bent 1929). Historically, many ne. U.S. shorebird migration–stopover locations exploited by market hunters for food and millinery trades (Doughty 1975), particularly New England, where turnstone numbers dropped markedly during second half of nineteenth century (Forbush 1912, Bent 1929). Since a high proportion of extant North American Ruddy Turnstone population (A. i. morinella) continues to move through traditional Atlantic coastal staging sites during spring migration, a monitoring program designed to track future trends is both feasible and necessary (see Morrison et al. 1999).

Information on population status of European race A. i. interpres in Arctic America also limited. No direct evidence of recent change in high-arctic Canada or Greenland, though decreases likely to have occurred during 1800s in response to heavy human persecution on wintering grounds (see Distribution: historical changes, above). Currently, little interyear variation in numbers of birds present on wintering grounds, which suggests a relatively stable population (Metcalfe and Furness 1985; Summers et al. 1989; Rose and Scott 1994, 1997). North American A. i. interpres population probably can be monitored effectively by counts of birds at spring-migration staging sites in Iceland (Gudmundsson and Gardarsson 1993) and at certain locations on wintering grounds in Britain (Branson et al. 1978, 1979; Metcalfe and Furness 1985; Rose and Scott 1997; R. I. G. Morrison pers. comm.).

Principal determinants of population sizes of both races of Ruddy Turnstones breeding in North America likely to be: availability of suitable habitat for nesting; adequate food supply on nesting territory for egg formation, self-maintenance during incubation, and early chick survival; and suitable food resources off territory for chick growth to fledging and buildup of energy reserves prior to fall exodus from breeding grounds to complete long-distance migratory flights between traditional staging areas. Factors important to adequate food reserves during winter season also critical to first-year survival, adult survival, and readiness of all age groups for spring migration.