Demography and Populations

Age At First Breeding; Intervals Between Breeding

Breeds first at 2–3 yr, on basis of return of adults banded first as chicks (n = 7; Flynn et al. 1999). Breeds yearly thereafter, but some evidence of skipping years from marked individuals in Churchill, Manitoba.

Clutch

Three to 4 eggs; typically 4 eggs/clutch, but more 3-egg clutches in year with particularly low temperatures (e.g., 1992 in Churchill, Manitoba; see Table 1). Typically 1 clutch/season; 2–8% of pairs renest/yr after loss of first clutch (EN).

Annual And Lifetime Reproductive Success

In Churchill, Manitoba (3 yr), mean number of young fledged per successful pair (those hatching chicks) was about 2.25–2.43 young (n = 10–19 pairs per year); 0.42–0.64 young fledged/laying female (n = 48–52 pairs per year). Of 23 broods monitored in Queen Charlotte Is., British Columbia, 11 contained 4 chicks, 9 contained 3, 2 contained 2, and 1 contained 1 (mean 3.3); hatching success 74.5% (35 of 47 nests; Cooper and Miller 1997). Higher fledging success than reported in Churchill.

Number Of Broods Normally Reared Per Season

Never >1 brood per season (EN).

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

In Churchill, Manitoba, proportion of pairs that successfully hatched at least 1 chick was 40.7–80.8% (average 60.8, n = 5 yr; Nol et al. 1997). Variation among years was negatively proportional to clutch completion dates: Years with early average completion dates had higher hatching success than years with later dates (n = 5 yr, r = –0.86, p = 0.06; EN). Proportion of pairs that fledged at least 1 chick varied from 22.0 to 48.6%, on basis of 3 yr of data (Y. Zharikov pers. comm., EN).

Oldest known breeding individual in Churchill, Manitoba, where population was studied 19881999, was 9 yr old, but 5- and 6-yr-olds made up 15% of breeding population (EN). Of all birds, 44–63% are first-time breeders (EN). Survivorship, as measured by return rates of banded breeders, was up to 60% for males; since females disperse in response to mate change (see Range, below), female return rates probably do not measure survivorship (Flynn 1997). SURGE analysis of adult survivorship gives estimates of 0.71 based on capture histories of 152 females and 142 males; no difference in survivorship estimates for males and females (D. Giesbrecht pers. comm.).

Diseases

No information.

Body Parasites

Feather lice common in Churchill, Manitoba (MSB), and on birds found during migration (EN). Of 5 shorebird species examined in Churchill, Semipalmated Plovers contained the most internal (all organs and blood) parasites, averaging 142 ± 198.5 SD individuals/bird (n = 122), 121 of 122 (99.2%) birds examined were infected (A. Didyk pers. comm.). Semipalmated Plovers also contained the most species, including cestodes, nematodes, digeneans, and acanthocephalans (A. Didyk pers. comm.). New species (Paraliga charadrii n. sp. [Cestoda: Dilepididae]) described from small intestine, collected from Manitoba (breeding), Bay of Fundy (fall migration), Venezuela (wintering), and Delaware Bay (spring migration), suggesting that transmission is ubiquitous (Didyk and Burt 1998). Feather mites include Bychovskiata semipalmati n. sp. (Avenzoariinae; Mironov and Dabert 1995).

Exposure

In years with low temperatures during incubation, greater proportion of eggs abandoned to exposure (Nol et al. 1997). Low body weights (<40 g) are seen in incubating birds exposed to freezing temperatures for 1 wk (M. Williamson pers. comm.).

Predation

Few data. Predators eat eggs, chicks, and adults in Churchill, Manitoba (Nol et al. 1997). Peregrine Falcons have been observed capturing foraging Semipalmated Plovers in Venezuela (A. Smith pers. comm.). Common Ravens took 3 of 6 clutches in Queen Charlotte Is., British Columbia (Cooper and Miller 1997). No information on mortality of adults, although Merlins (Falco columbarius) took other small shorebirds at James Bay (R. I. G. Morrison pers. comm.).

Competition With Other Species

Competition with Killdeer at Churchill (Manitoba) or Queen Charlotte Is. (British Columbia) is possible because of similarity in nesting habitat, but Killdeer generally feed on drier substrate than Semipalmated Plovers both in Churchill and elsewhere (e.g., coastal Virginia; EN). One case of interspecific aggression between Killdeer and Semipalmated Plover on migration grounds (Recher and Recher 1969).

Initial Dispersal From Natal Site

Only 7 of 445 (1.6%) hatchlings banded in Churchill, Manitoba, returned there in a subsequent year (Flynn et al. 1999). No yearling breeders (EN).

Fidelity To Breeding Site And Winter Home Range

Fidelity to winter home range unknown. In Churchill, 58.9% of (n = 95) adult males and 41.2% of (n = 102) females returned to breeding area. Males usually return to same territory (mean movement 40 m ± 12 SE, n = 35). Females move after change of mate (through divorce, loss, or lack of return of previous mate) up to 5 km (mean 576 m ± 216 SE, n = 18; Flynn et al. 1999). For both sexes, success in the previous year resulted in higher return rates (Flynn et al. 1999). Females that experienced breeding failure and changed mates in the subsequent breeding season moved farther from failed nest sites than did females that were successful and changed mates (Flynn et al. 1999).

Home Range

During breeding season, up to 3 km²; not known during winter or migration.

No evidence of decrease in numbers along migration or at migration stopover areas (Howe et al. 1989, Morrison et al. 1994). Total population near Masset, Queen Charlotte Is., British Columbia, estimated at 31–34 pairs (Cooper and Miller 1997); total for island probably about 100 pairs (EN). Churchill, Manitoba, population estimated at 70 pairs (W. Jehl and J. R. Lin unpubl.). Density along Ontario coast is 11–100 breeding pairs/10 km², 2–10/km²on riverbeds (Hussell 1987); densities of 13–14 pairs/km²in outer Mackenzie Delta, Northwest Territories (Gratto-Trevor 1996). Estimate for entire breeding range (12,000 km²) based on these densities: 13,200–120,000 breeding pairs. Estimates based on wintering numbers or numbers during migration probably are lower (20,000–30,000 individuals), but poor coverage along most of n. South American shoreline where species concentrates.

Breeding population in Churchill, Manitoba, was very stable during 9 yr of study (1988, 1992–1999). Return rates vary tremendously among years, suggesting that factors on wintering grounds might limit breeding densities. After El Niño event of winter 1997–1998, low return rate to breeding grounds at Churchill (<30%; EN) and Prudhoe Bay, AK (15%; R. Lanctot pers. comm.).