Demography and Populations

Measures Of Breeding Activity

Age At First Breeding; Intervals Between Breeding

Except for over-wintering birds (see Migration: 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 easily distinguished by worn Juvenal primaries (see Appearance: molts and plumages, below), and both sexes known to breed, males possibly with greater frequency (Johnson et al. 1993); similar worn Juvenal primaries not evident in American Golden-Plovers (this species apparently replaces flight feathers during first winter), thus 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, lack of food, and lemming cycle (see below) may prevent breeding or dramatically reduce nesting densities in some seasons (Fay and Cade 1959, Hussell and Holroyd 1974, Montgomerie et al. 1983, Tomkovich and Sorokin 1983, Kondratiev 1992, Johnson et al. 1993, Troy 1996, Exo and Stepanova 2000, Jehl, 2004, Latour et al. 2005, Johnston and Pepper 2009).

Clutch

Four eggs/clutch typical in American Golden-Plover (n = 92; Parmelee et al. 1967, Jehl and Smith 1970, Moiteret et al. 1996, OWJ); also in Pacific Golden-Plover (n = 117; Kondratiev 1982, WFVZ collection, Tulp et al. 2000, OWJ). However, clutch samples often average <4 eggs: American Golden-Plover, 3.7 (n = 21; WFVZ collection); 3.8 (n = 26; Moiteret et al. 1996); Pacific Golden-Plover, 3.9 and 3.7 (n = 7 and 6; Underhill et al. 1993); 3.6 (n = 7; Schekkerman and van Roomen 1995); 3.9 (n = 76; Schekkerman et al. 2004). To what extent the latter findings affected by incompletion of clutches, partial depredation, or replacement clutches of less than 4 eggs is unknown. An unusual clutch of 8 eggs (gradually “depredated one by one”) reported in American Golden-Plover (Byrkjedal 1989a), and two 5-egg Pacific Golden-Plover clutches found on Seward Peninsula (OWJ). . Presumably, any number >4 represents egg-dumping.

Replacement laying after nest loss together with between-clutch mate fidelity occurs in both species (Sviridova 2000, Klima 2002, Schekkerman et al. 2004, Tulp 2007, Johnson et al. 2008b). Downward trend in body mass found among female Pacific Golden-Plovers starting incubation later in the season (also similar trend in egg mass) probably reflects the demands of producing replacement clutches (Tulp et al. 2000, Tulp and Schekkerman 2001).

Annual And Lifetime Reproductive Success

No information on lifetime success. Various measures of annual success (percent total nests producing young, mean number of young/nest, mean number of chicks fledged/pair) needing study in these species.

Considerable variation in annual success because of seasonally variable losses of eggs and chicks and/or failure to breed. Examples: American Golden-Plover, 6 of 21 (28.6%) nests lost near Churchill (Byrkjedal 1989a); overall hatching success approximately 47% from 1989-1992 near Prudhoe Bay, Alaska (Moiteret et al. 1996); at least (some birds still incubating when observations ended) 5 of 10 (50%) nests destroyed on Seward Peninsula 1993 (OWJ); Pacific Golden-Plover, 2 of 8 (25%) nests destroyed Seward Peninsula 1993 (OWJ); losses of nests/broods at study sites on the Taimyr Peninsula varied from total to about 50% over period from 1993-2002 (Tomkovich 1994, Tomkovich and Zharikov 1998, Sviridova 2000, Schekkerman et al. 2004).

Life Span And Survivorship

Among territorial Pacific Golden-Plovers captured as first-year birds on Oahu, HI (n = 34), average life span was approximately 6 yr; for those captured as unknown-age adults (n = 78), estimated mean post-banding life expectancy was 4.5 yr; however, 9 of the latter birds survived ≥10 seasons post-banding and 1 individual (a male) was last seen on his winter territory at a minimum age of 21 yr 3 mo, this being a longevity record for the species (Johnson et al. 2001c, 2004b). On the Taimyr Peninsula, Pacific Golden-Plovers (marked males) known to nest at study site for at least 8 seasons (Tulp and Schekkerman 2001). Long-term nesting records through 2009 on the Seward Peninsula are the same (8 post-banding seasons) for several males of both species (OWJ and P. Bruner, unpubl. data); one exceptional male American Golden-Plover returned for 12 post-banding seasons, thus minimum age was 13 yr when last observed (Johnson et al. 2007b). The latter is a longevity record for the species

Diseases And Body Parasites

Extensive investigation of Pacific Golden-Plovers (220 specimens) by Okimoto (1975). Okimoto’s findings and his review of literature indicate the following external and internal parasites from plovers collected on Hawaii wintering grounds: feather mites (probably families Dermaglyphidae, Proctophyllodidae, Pterolichidae); chewing lice (Saemundssonia sp., Quadraceps sp., Colphocephalum sp.); nasal mites (Rhinonyssidae); chiggers (Neoschoengastia sp.); eyeworm (Oxyspirura mansoni); acanthocephalans (Plagiorhynchus charadrii, Mediorhynchus orientalis); cecal worm (Subulura skrjabinensis); nematodes (Porrocaecum semiteres, P. ensicaudatum); trematodes (Heterophyidae); and unidentified cestodes. Blood smears were negative for haematozoons and avian influenza. Incidence of internal parasites varied greatly in Hawaii (high at some sites, low or absent at others), leading Okimoto to suggest that populations are distinct groupings with little intra- or inter-island mingling during the wintering season. This interpretation is consistent with winter site fidelity observations (see Range, below).

Reports of Pacific Golden-Plover parasites from various regions of the world include: acanthocephalans (Plagiorhynchus charadrii, Arythmorhynchus petrochenkoi, Filicollis anatis, Sphaerirostris areolatus, and Mediorhynchus papillosus) [Soota et al. 1971, Smith and Guest 1974, Khokhlova 1986]; nematode (Microtetrameres plovericus) [Sharma 1970]; trematodes (Echinostoma charadrii, Eumegacetes sp., Acanthoparyphium cambellensis, Maritrema macropharynga, M. papillorobusta, and Levinseniella howensis) [Tubangui and Masiluñgan 1935, Soota et al. 1970, Ke 1976, Pearson and Deblock 1979 ]; cestodes (Anomotaenia globulus, A. ericetorum, Polycercus sp., Liga brevis, and Paricterotaenia sp., Paraprogynotaenia charadrii and Paraprogynotaenia canarisi) [Belopolskaya 1977, 1979, Tomilovskaya 1979, Jensen et al. 1983, Nikolov and Georgiev 2008]; chiggers, lice, and mites (Acariscus pluvius, A. anous, Neoschoengastia carveri, N. ewingi, N. namrui, N. gallinarum, Toritrombicula shiraii, T. oahuensis, T. oceanica, Actornithophilus ochraceus, Quadraceps charadrii, Saemundssonia conica, Plutarchusia paralongitarsa) [Wharton 1946; see Loomis 1966; Brennan and Amerson 1971; Goff 1971,1977; Amerson and Emerson 1971; Dabert and Ehrnsberger 1990]; hippoboscid flies (Ornithoica pusilla and Olfersia aenescens) [Maa 1968]. Avian malaria (Plasmodium relictum) found in one specimen from NW Hawaiian Is. (Beadell et al. 2006). No avian malaria (Plasmodium or Haemoproteus) in birds (n = 11) from Taimyr Peninsula (Mendes et al. 2005).

Studies of American Golden-Plovers much less extensive: only known parasites appear to be chewing lice (Actornitophilus timidus, Quadraceps orarius, and Philopterus conicus) [Peters 1936, Orfila 1959]; and nasal mite (Rhinonyssus pluvialis) [Fain and Johnston 1966]. No blood parasites in this plover (n = 5) collected in North America (Greiner et al. 1975).

Causes Of Mortality

Effects of extreme weather and collisions with man-made structures (see Newton 2007 for general review) mostly undocumented. Hailstones sometimes kill and injure American Golden-Plovers on the pampas (Hudson 1918). Unpublished record during spring migration 2008 of exhausted Pacific Golden-Plover (a male banded by OWJ on Oahu) landing in dense fog on a fishing vessel in the Bering Sea suggests such weather conditions cause mortality in that region. A severe storm on Oahu, HI, wintering ground caused no apparent losses of Pacific Golden-Plovers (Johnson et al. 1981). Nothing known concerning competition with other species, or pesticide-related mortality. Both plovers exposed to wide array of agrichemicals (see Conservation and Management: effects of human activity, below). Feeding on poisoned bait set out for herons has caused accidental losses of Pacific Golden-Plovers in India (P. O. Nameer in litt.).

Little detailed knowledge of avian predation during the breeding season. Rough-legged Hawks (Buteo lagopus), Gyrfalcons, and especially Peregrine Falcons (Falco peregrinus) all take plovers (White and Weeden 1966, White and Cade 1971, White et al. 1973, Springer 1975). Parasitic and Long-tailed jaegers prey mostly on chicks and young birds (Maher 1974). Snowy Owl (Nyctea scandiaca) is a potential predator, but only 1 adult American Golden-Plover was found among remains of 15,078 prey (almost entirely lemmings) from nests near Barrow, AK (D. Holt pers. comm.). Other avian predators of possible significance include Pomarine Jaeger, Short-eared Owl (Asio flammeus), and Common Raven.

Lemming cycles apparently of major significance to nesting success. In peak years, arctic fox and various raptors consume lemmings almost exclusively; as lemmings decline, situation reverses since predators switch to diet of eggs and chicks. Numerous observers have reported these alternating scenarios on the Siberian breeding grounds, with near reproductive failure in some seasons (e.g., Underhill et al. 1993, Schekkerman and van Roomen 1995, Byrkjedal and Thompson 1998, Ryabitsev 2000, Schekkerman et al. 2004). Similar findings in arctic Alaska (Troy 1996) and Southampton I. (Smith et al. 2007). Remote camera studies in the Prudhoe Bay region suggest that arctic foxes (among various potential predators, mostly avian) are responsible for shorebird nest depredation more often than previously recognized (Liebezeit and Zack 2008).

Caribou and reindeer are known to trample nests and eat eggs or young of tundra-nesting birds (Wright 1979, Tomkovich and Zharikov 1997, de Roos 1997, Tulp and Schekkerman 2001, also see Soloviev and Tomkovich 2003-2008). This occurred with several nests of both species 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.

Established, resident Pacific Golden-Plovers on Oahu, HI, wintering grounds show 80+% year-to-year survival rates, indicating that annual mortality involves mostly juveniles. After depletion of energy reserves during their first southward migration, inexperienced young birds arrive on winter ranges already occupied by adults, with which they must compete. Dead and dying juveniles (in emaciated condition) are relatively common during fall and winter in the nw. Hawaiian I. (Johnson et al. 1989, B. McCaffery pers. comm.), similar mortality observed at Johnston Atoll (Johnson et al. 2004c); undetected starvation-caused losses are likely elsewhere on the winter range. Presumably, juvenile American Golden-Plovers face similar problems, although winter ranges on South American grasslands might offer more resources than the insular Pacific (Johnson 1985).

Losses of wintering American and Pacific golden-plovers to predation are poorly understood (see Conservation and Management: effects of human activity, below). Raptors may cause significant losses, and both golden-plovers show predictable responses to this threat (see Behavior: predation, above). In Hawaii, the Barn Owl, Short-eared Owl, feral house cat, and mongoose (Hespestes auropunctatus) are potential Pacific Golden-Plover predators. Pellet and scat analyses from the first three showed low incidence of plover predation by Short-eared Owl only (Snetsinger et al. 1994). However, Pacific Golden-Plover remains were found at a Barn Owl roost on Kaula I., HI (R. Walker pers. comm.), and a Barn Owl attempted to capture a plover on Maui, HI (P. Bruner pers. comm.). Better assessment of owl, cat, and mongoose predation awaits additional studies. Habit of roosting on roofs in Hawaii (see Behavior: self-maintenance, above) lessens threat from cats.

Range

Natal Philopatry And Dispersal

No information.

Fidelity To Breeding Site

Studies of marked birds both species from 1988-2003 on the Seward Peninsula showed males much more site-faithful than females, following details from Johnson et al. (1993, 1997a, 2001b, 2007b). Returnees observed in one or more post-banding seasons: American Golden-Plover, 13 of 19 males (68%), 3 of 15 females (20%); Pacific Golden-Plover, 12 of 16 males (75%), 2 of 12 females (17%). All males reoccupied the same territories annually. One of the American Golden-Plover females 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 last year’s 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. The two female Pacific Golden-Plover returnees were found only in their first and second post-banding seasons. One bird paired with a different male on a territory near to where she had been banded, then mated with this same male again in season 2. The other female returned to the site where she had been captured and reunited with the same male in both post-banding seasons 1 and 2 (i.e., the same pairing three consecutive times).

From the inter-year distances mentioned above for females, it is apparent that at least some females return to the same general breeding locale but often are not site-specific enough to be detected. Similar findings were reported by Klima (2002) who located a marked female American Golden-Plover nesting at “slightly over 1 km” from her study area, by Sviridova (2000) who found a female Pacific Golden-Plover nesting at 924 m from her previous nest and another female that likely was nesting at 1.5-2 km, and by Ryabitsev (2000) who discovered two females of the congeneric Black-bellied Plover (these had been missing from his study plot on the Yamal Peninsula for two years) nesting at distances of 2 km and 4 km, respectively. Of 3 instances in which both members of pairs returned in the first season after banding on nw. Taimyr Peninsula, 1 pair divorced, 1 reunited, and in 1 the status was uncertain as the female was observed with a previous mate and also a different male (Schekkerman et al. 2004). All the foregoing concerning female site fidelity indicates that reunion of the same pairs is infrequent and unlikely in these 3 Pluvialis plovers. 

The range of interyear distances between nests of marked males varies widely: American Golden-Plover, 0 m (reuse of cup) to 500 m, n = 12, Seward Peninsula (Johnson et al. 2001b, 2007b), 46-289 m, n = 3, North Slope, AK (Moiteret et al. 1996); Pacific Golden-Plover, 100-450 m, n = 3, nw. Taimyr Peninsula and 15-530 m, n = 16, se. Taimyr Peninsula (Sviridova 2000), 0 (reuse) to 420 m, n = 24, Seward Peninsula (Johnson et al. 2001b, OWJ), 8-432 m, n = 12, nw. Taimyr Peninsula (Schekkerman et al. 2004). Distances between first nests and replacement nests (see above) for Pacific Golden-Plovers: 66-330 m, n = 3, nw. Taimyr Peninsula (Schekkerman et al. 2004), 74-457 m, n = 4, Seward Peninsula (Johnson et al. 2008b).

Other fidelity records over consecutive post-banding seasons: American Golden-Plover, 4 of 7 males and 0 of 2 females returned at site on North Slope, AK, 3 seasons (Moiteret et al.1996), male return rate 72%, female 41%, 3 seasons, Churchill (see Klima and Johnson 2005); Pacific Golden-Plover, 11 of 22 males (50%) and 2 of 23 females (8.7%), 2 seasons, se. Taimyr Peninsula and 3 of 8 males (37.5%), and 0 of 6 females, 1 season, nw. Taimyr Peninsula (Sviridova 2000); 25 of 39 birds (64%) no clear indication of any difference between sexes, 2 seasons, nw. Taimyr Peninsula (Schekkerman et al. 2004); 3 of 4 birds (sexes not indicated) returned, 1 season, ne. Taimyr Peninsula (Underhill et al. 1993); and a female marked by Tomkovich and Vronski (1988) nested at the same site nw. Taimyr Peninsula, 2 seasons. Overall conclusion about breeding ground fidelity: when compared to various species of monogamous shorebirds, American and Pacific golden-plovers (also the Black-bellied Plover) are notable for significant gender bias with interyear returns to specific nesting territories strongly favoring males (Klima and Johnson 2005).

Fidelity To Winter Site

High return rates typical in Pacific Golden-Plovers on Oahu study areas (see above). Territorial birds reoccupy same territories, and non-territorial birds frequent same sites annually (Johnson et al. 1981, 1989, 2001c, OWJ and P. Bruner unpubl. data). The same pattern was found at wintering grounds on Johnston I., Saipan I., and American Samoa (Johnson et al. 2004c, 2006, 2008a). No other comparable studies elsewhere on Pacific Golden-Plover winter range. Fidelity probably similar in American Golden-Plover, but no information.

Home Range

When not incubating, breeding birds (especially females) move to feeding grounds, often at considerable distance from nest (Sauer 1962, Byrkjedal and Thompson 1998). Some individuals on Seward Peninsula move at least 3 km, with more extended flights likely (OWJ). On winter range in Argentina, American Golden-Plovers travel about 4–6 km to reach nighttime roosts (Myers 1984); on Oahu, Pacific Golden-Plovers move variable distances to at least 4 km (OWJ). Movements of Pacific Golden-Plover probably much greater where birds feeding in high-elevation environments (e.g., on island of Hawaii) return to rooftop, coastal, or hillside roosts.

Population Status

Numbers

Current knowledge limited to estimates of uncertain accuracy: American Golden-Plover, 200,000 (Morrison et al. 2006); Pacific Golden-Plover, 185,000-250,000 (Delaney and Scott 2006), 100,000-1,000,000 (Bamford et al. (2008). Of the world’s Pacific Golden-Plover population, Morrison et al. (2006) estimate that 35,000-50,000 breed in Alaska.

Estimates of 1.0-2.5 million pairs for American Golden-Plover and 1.1-2.6 million pairs for Pacific Golden-Plover (Byrkjedal and Thompson 1998) 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). From sampling in representative habitats, Schwartz and Schwartz (1949) estimated 74,000 Pacific Golden-Plovers wintering in main Hawaiian I.; Giffin and Medeiros (1968) estimated 15,173 Pacific Golden-Plovers on island of Oahu. Of the total world population, the number of Pacific Golden-Plovers wintering at the far southern end of the range is relatively small (estimates: 7,500 Australia [Bamford et al. 2008]; 229-649 New Zealand [Sagar et al. 1999, Southey 2009]).

Estimated densities (pairs/km²) on breeding grounds vary significantly between regions and from year-to-year: American Golden-Plover, 0.4-6.1 Alaska, Canadian arctic and subarctic (see Byrkjedal and Thompson 1998); 3.0 on Seward Peninsula 1993 (OWJ); 4.0 on Arctic National Wildlife Refuge, AK (Spindler 1978); 6.0-15 at Barrow, AK (see Lowe 1994,1995); 1.0-2.9 near Prudhoe Bay, AK (Moiteret et al. 1996); 0.3-6.4 on 13 sites across the arctic breeding range (see Johnston and Pepper 2009);

Pacific Golden-Plover (pairs/km² ): 0.1-6.7 Yamal, Taimyr, Chukchi Peninsulas, Koryak Mtns., Russia (see Byrkjedal and Thompson 1998); 0.5-7.5 nw. Taimyr Peninsula (Schekkerman and van Roomen 1995; Tomkovich and Zharikov 1998; Tulp et al. 1997, 2000; Tulp and Schekkerman 2001; Schekkerman et al. 2004); 2-5 Lena Delta, Russia (Tomkovich and Zharikov 1998, Exo and Stepanova 2000); 0.66 on Yukon-Kuskokwim Delta, AK 1988-1992 (McCaffery 1996); 2.0 on Seward Peninsula 1993 (OWJ). Nesting densities of Pacific Golden-Plovers higher than those listed above possibly occur in unusually favorable habitats, however reports of “up to 80 birds/km²” (see Rogacheva 1992) seem unlikely. Large numbers of American Golden-Plovers breed on the coastal plain of the Arctic National Wildlife Refuge, AK. Sampling by Brown et al. (2007) indicated the plain hosts approximately 8% of world’s population as estimated by Morrison et al. (2006).

Estimated densities on wintering grounds (birds/ha): American Golden-Plover, 10.0+ on grazed pampas of Argentina (Myers and Myers 1979); Pacific Golden-Plover, 0.22–44.7 in various habitats ranging from forest trails to coastal mudflats, Oahu (Morita and Walker 1964, Giffin and Medeiros 1968), 1.4 on golf courses, Oahu (Johnson and Johnson 1993c), 5.2 on lawns of National Cemetery of the Pacific, Oahu (OWJ), 8.0 on slopes of Mauna Kea at 2,380 m elevation, Hawaii I. (Van Riper et al. 1978), 3.0 on golf course, American Samoa (Johnson et al. 2008a).

Trends

Status of both species remains uncertain; increased population monitoring needed (see Johnson 2003, Clay et al. 2009).

American Golden-Plover: Trends unclear and reports often conflicting; increasing numbers of breeding birds recorded on Devon I., 1978 to 1989 (Pattie 1990), at Churchill, ON, 1930 to 1990s (Jehl and Lin 2001, Jehl 2004), and on Prince Charles and Air Force Is., NU, 1989 to 1997 (Johnston and Pepper 2009); major decline from 1975 to 1995 in Rasmussen Lowlands, NU (Gratto-Trevor et al. 1998, Johnston et al. 2000); fall migration data 1974-1998 from North America suggest downward trend in n. Atlantic region, increase in Midwest (Bart et al. 2007); Morrison et al. (2006) consider the species to be declining, however in 2008 USFWS analyses of shorebird trend datasets the species was listed as stable (B. Andres, in litt.); no meaningful trend counts from wintering grounds or along migratory routes to/from North America.

Pacific Golden-Plover: No useful trend data from either the breeding or non-breeding ranges; Morrison et al. (2006) indicate species in decline, Andres (in litt.) considers trend unknown; apparent declines in Australia and New Zealand (Harris 1994, Wilson 2001, Gosbell and Clemens 2006, Southey 2009) may be due to “short-stopping” elsewhere (see Habitat: winter range, above).

Both species: Populations may be declining for various reasons (see Conservation and Management, below), but objective assessments will require intensive systematic monitoring at stopover areas and on breeding and non-breeding grounds.

Population Regulation

Little specific information. Likely factors include vagaries of weather and food supply on breeding grounds (as reflected by variation in nesting densities cited above), egg and chick predation, loss of juveniles from rigors of first migration and/or competition on wintering grounds, and predation on winter range.

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