Demography and Populations
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Measures of Breeding Activity
Age at First Breeding; Intervals Between Breeding
Except for overwintering birds (see Distribution, Migration and Habitat: Timing and Routes), almost all first-year American Golden-Plovers and many first-year Pacific Golden-Plovers return to nesting grounds. Of these, Pacific Golden-Plovers are distinguished by worn juvenile primaries (see Appearance: Plumages and Appearance: Molts), and both sexes are known to breed, males possibly with greater frequency (260). Similar age criterion are not present in American Golden-Plover as this species molts primaries during first its first overwintering period (13), thus it is more difficult to confirm probable breeding by first-year individuals. Most birds attempt to nest each year, but local and regional variables such as late snow melt may prevent breeding or dramatically reduce nesting densities in some seasons (147, 174, 260, 244, 177, 261, 146).
Four eggs per clutch is typical in American Pacific Golden-Plover (44, 143, 243, OWJ). However, clutch samples often average less than 4 eggs [e.g., 3.7 eggs (n = 21 clutches, WFVZ collection); 3.8 eggs (n = 26 clutches, 243)], presumably owing to partial depredation, or replacement clutches of less than 4 eggs. An unusual clutch of 8 eggs (gradually “depredated one by one”) was reported at Churchill, Manitoba (176), likely involved egg-dumping. Replacement laying after nest loss together with between-clutch mate fidelity has been documented in both American and Pacific golden-plovers (173, 247).
Annual and Lifetime Reproductive Success
No information on lifetime success. Considerable variation in annual success because of seasonally variable losses of eggs and chicks and/or failure to breed. For example, 6 of 21 (28.6%) nests lost near Churchill (176); 47% overall hatching success from 1989–1992 near Prudhoe Bay, Alaska (243); at least 5 of 10 (50%) nests destroyed in 1993 on Seward Peninsula, Alaska, some birds still incubating when observations ended (OWJ).
Life Span and Survivorship
Best known in Pacific Golden-Plover (see 16). On the Taimyr Peninsula, Far North Russia, marked Pacific Golden-Plover males nested at the study site for at least 8 seasons (262). Long-term nesting records for American and Pacific golden-plovers on the Seward Peninsula, Alaska suggest similar longevity; several males of both species returned for 8 consecutive seasons (OWJ and P. Bruner, unpublished data). Two exceptional American Golden-Plovers have been documented: a female at least 12 years of age (Churchill, Manitoba, 263), and a male at least 13 years of age (Seward Peninsula, Alaska); the latter being the longevity record for the species (173). An annual adult survival rate of 0.72 was estimated from survival modeling at 9 breeding sites across the North American arctic and subarctic (264).
Disease and Body Parasites
American Golden-Plovers are known to harbor chewing lice (Actornitophilus timidus, Quadraceps orarius, Philopterus conicus) (265, 266); and a nasal mite (Rhinonyssus pluvialis) (267). No blood parasites were detected in sample of 5 individuals collected in North America (268). Parasites have been extensively studied in Pacific Golden-Plover (see 16).
Effects of extreme weather and collisions with man-made structures (see 269 for a general review) are mostly undocumented. Hailstones sometimes kill and injure plovers on the pampas (270). Exposed to wide array of agrochemicals (see Conservation and Management: Effects of Human Activity), but no information on pesticide-related mortality. Nothing is known about mortality resulting from intraspecific or interspecific competition.
Little detailed knowledge of avian depredation during the breeding season. Rough-legged Hawk (Buteo lagopus), Gyrfalcon (Falco rusticolus), and especially Peregrine Falcon (Falco peregrinus) all take plovers (271, 272, 273, 274). Parasitic and Long-tailed jaegers prey mostly on chicks and young birds (275). Snowy Owl (Bubo scandiacus) is a potential predator, but only one adult plover was found among remains of 15,078 prey (almost entirely lemmings) from owl nests near Barrow, Alaska (D. Holt, personal communication). Other avian predators of possible significance include Pomarine Jaeger (Stercorarius pomarinus), Short-eared Owl (Asio flammeus), and Common Raven (Corvus corax).
Lemming cycles are apparently of major significance to nesting success of golden-plovers. In peak years, Arctic Fox and various raptors consume lemmings almost exclusively; as lemmings decline, predators switch to diet of eggs and chicks. Numerous observers have reported these alternating scenarios on the Siberian breeding grounds of the Pacific Golden-Plover, with near reproductive failure in some seasons (e.g., 276, 277, 31, 278, 279). Similar findings in arctic Alaska (244) and Southampton Island, Nunavut (280). Remote camera studies in the Prudhoe Bay region suggest that Arctic Fox (among various potential predators, mostly avian) are responsible for shorebird nest depredation more often than previously recognized (281).
Caribou and Reindeer are known to trample nests and eat eggs or young of tundra-nesting birds (282, 283, 284, 262). This occurred with several nests under observation on Seward Peninsula in summer 1993 (OWJ). Chance passage of a large herd of these animals through local area likely to destroy most plover nests. No specific information concerning depredation during the overwintering period.
Natal Philopatry and Dispersal
Fidelity to Breeding Site
Studies of marked birds from 1988–2003 on the Seward Peninsula showed males much more site-faithful than females (231, 232, 173). Most males (13 of 19, 68%) were observed in one or more post-banding seasons, fewer females (3 of 15, 20%). All males reoccupied the same territories. One female went unseen for 3 post-banding seasons, then was found in season 4 paired with a marked male (a different mate than she had when captured) at a site approximately 1,200 m from the nest where she was originally banded. In post-banding season 5, this female observed again (the last sighting), but only briefly during a skirmish with her season 4 mate (already paired with another female) who chased her away. The other two American Golden-Plover females were found in their first post-banding seasons, unseen thereafter. Both had different mates and were nesting approximately 550 m and 1,600 m, respectively, from their previous season nests. From these inter-year distances, it is apparent that females may return to the same breeding locale but are not site-specific enough to be detected. Similar findings were reported by Klima (285) who located a marked female nesting at “slightly over 1 km” from her study area. Distances up to 5 km are known in Pacific Golden-Plovers (see 16). The range of interyear distances between nests of marked males varies widely: 0 m (reuse of cup) to 500 m (n = 12) on the Seward Peninsula (232, 173); and 46–289 m (n = 3) in North Slope, Alaska (243).
Other fidelity records over consecutive post-banding seasons: 4 of 7 males and 0 of 2 females returned at site on North Slope, Alaska, 3 seasons (243); male return rate 72%, female 41%, 3 seasons, Churchill (see 286). Overall conclusion about breeding ground fidelity: when compared to various species of monogamous shorebirds, American Golden-Plover (also Pacific Golden-Plover and Black-bellied Plover) is notable for significant gender bias with interyear returns to specific nesting territories strongly favoring males (286).
Fidelity to Overwintering Site
High return rates typical in Pacific Golden-Plovers (see 16). Fidelity probably similar in American Golden-Plover, but no information.
When not incubating, breeding birds (especially females) move to feeding grounds, often at considerable distance from nest (31). Some individuals on Seward Peninsula move at least 3 km, with more extended flights likely (OWJ). On overwintering range in Argentina, plovers travel about 4–6 km to reach nighttime roosts (226).
Population size remains uncertain and increased population monitoring is needed (see Clay et al. ). Program for Regional and International Shorebird Monitoring (PRISM) surveys on the breeding grounds (287) indicated that a previous population estimate of 200,000 individuals (288) was too low. Based on the PRISM surveys, Andres et al. (289) estimated a total population of 500,000 (possibly conservative because alpine nesting grounds were not surveyed), with about 50% in Alaska and 50% in Canada. Estimates of 1.0–2.5 million pairs (31) are likely too optimistic. These high numbers were extrapolations based on overall breeding range and average nesting density; however, breeding distribution is often patchy and what appears to be suitable habitat may contain no birds (OWJ).
Estimated breeding densities vary significantly between regions and from year to year; e.g., 0.4–6.1 pairs/km2 in Alaska, Canadian arctic and subarctic (31); 3.0 pairs/km2 on Seward Peninsula in 1993 (OWJ); 4.0 pairs/km2 on Arctic National Wildlife Refuge, Alaska (256); 6.0–15 pairs/km2 at Barrow, Alaska (see 290, 291); 1.0–2.9 pairs/km2 near Prudhoe Bay, Alaska (243); 0.3–6.4 pairs/km2 on 13 sites across the arctic breeding range (see 146); and 0.2–40 birds/km2 in Nunavut (77). Estimated densities on overwintering grounds were 10.0+ birds/ha on grazed pampas of Argentina (121).
Population trends are unclear and reports often conflicting. In 2006, Morrison et al. (288) considered the species to be declining in North America; more recently, Andres et al. (289) ranked the population as apparently stable, trend unknown. Other observations: Increasing numbers of breeding birds were recorded on Devon Island, Nunavut, 1978 to 1989 (259), at Churchill, Manitoba, 1930 to 1990s (292, 177), and on Prince Charles Island and Air Force Island, Nunavut, 1989 to 1997 (146); major decline from 1975 to 1995 in Rasmussen Lowlands, Nunavut (293, 294; for additional comments concerning Nunavut, see Richards and Gaston ); downward trend during fall migrations (1974–1998) in Atlantic Canada and northeastern U.S., and an increase in the Midwest (295); probable declines on overwintering grounds in southeastern South America (182).
If populations are declining for various reasons (see Conservation and Management), objective assessments will require intensive systematic monitoring at stopover areas and on breeding and nonbreeding grounds.
Little specific information about how populations are affected by vagaries of weather and food supply on migratory routes and breeding/overwintering grounds, depredation of eggs and chicks, mortality of juveniles from rigors of first migration and/or competition on overwintering grounds, and depredation on the overwintering grounds. Aside from these factors, looms the specter of climate change and other anthropogenic impacts ( see Conservation and Management).