Piping plovers have been observed as early as February 24 in Virginia (Cross 1991), March 11 in New York (Goldin 1990), March 15 in Massachusetts (MacIvor 1990), and March 28 in Nova Scotia (Mills 1976, cited in Cairns 1977). Cross (1991) reported that feeding was the most common plover activity during March in Virginia. Cairns (1977) also reports early season flocking of unpaired birds in neutral feeding areas (i.e., areas not defended through territorial behaviors) in Nova Scotia.
By early April, males begin to establish territories (Patterson 1988, MacIvor 1990, Cross 1991), which they defend aggressively against adjacent males by performing "horizontal threat," "parallel run," and aerial displays, characterized by Cairns (1982). Parallel runs may cover distances up to 100 meters, while aerial displays may be performed from just above ground level up to approximately 35 m and are generally accompanied by continuous vocalization. Courtship rituals include tilt displays, tossing of shell fragments, and scraping of multiple shallow depressions in the sand. Cairns (1982) also provides descriptions of copulatory activities.
Piping plovers are monogamous, but usually shift mates between years (Wilcox 1959, Haig and Oring 1988c, MacIvor 1990) and, less frequently, between nesting attempts in a given year (Haig and Oring 1988c, MacIvor 1990, Strauss 1990) Plovers are known to breed at one year of age (MacIvor 1990, Strauss 1990, Haig 1992), but the rate at which this occurs is unknown.
Piping plover nests are situated above the high tide line on coastal beaches, sandflats at the ends of sandspits and barrier islands, gently sloping foredunes, blowout areas behind primary dunes, and washover areas cut into or between dunes. They may also nest on areas where suitable dredge material has been deposited. Nest sites are shallow scraped depressions in substrates ranging from fine grained sand to mixtures of sand and pebbles, shells or cobble (Bent 1929, Burger 1987a, Cairns 1982, Patterson 1988, Flemming et al. 1990, MacIvor 1990, Strauss 1990). Nests are usually found in areas with little or no vegetation although, on occasion, piping plovers will nest under stands of American beachgrass (Ammophila breviligulata) or other vegetation (Patterson 1988, Flemming et al. 1990, MacIvor 1990).
Piping plovers are territorial nesters, defending both nesting and brood rearing territories from conspecifics (Wilcox 1959, Cairns 1977). Observed nesting densities are highly variable, however. Wilcox (1959) reported that nests of adjacent pairs are usually spaced 200 feet or more apart and are seldom closer than 100 feet. Nests in Cairns' (1977) primary study area in Nova Scotia averaged about 50 m apart, but the shortest distance between two simultaneously active nests was 3 m. Elias-Gerken (1994) noted contrasting densities of pairs within her study area on New York's central barrier islands; in 1992, she located 2.1 pairs per kilometer on Westhampton Island and 1.8 pairs per km on Jones Island, compared with 0.2 pairs per km on Fire Island.
Data gathered to date at New England sites where productivity has been high and the population has increased in recent years suggest that, at most sites, observed nesting densities may be a function of available breeding birds, which may be limited because of depressed productivity for many years. Dramatic increases in breeding densities have occurred without declines in productivity that might suggest overcrowding. For example, the piping plover population on the Cape Cod National Seashore in Massachusetts increased from 13 pairs in 1988 to 72 pairs in 1994, while average productivity in the same area increased from 0.9 chicks per pair in 1988 to 2.1 and 2.5 chicks per pair in 1993 and 1994, respectively (Brown and Hoopes 1993; S.M. Melvin, Massachusetts Division of Fisheries and Wildlife, in litt. 1994). Similarly, the number of breeding pairs at Crane Beach, Massachusetts increased from five pairs in 1986 to 18 in 1993; the lowest productivity recorded on the site during this period was 1.8 chicks per pair in 1990 (Rimmer 1994). In Maine, 15 pairs with average productivity of 1.7 chicks per pair nested at Seawall/Popham/Hunnewell Beach in 1993, where only two pairs were recorded in 1981 (J. Jones, Maine Audubon Society, in litt. 1992, 1993). The nesting population on about 8 hectares at Goosewing Beach in Rhode Island increased from three pairs in 1986 to nine pairs in 1994, when productivity was over 2.6 chicks per pair (C. Raithel, Rhode Island Division of Fish and Wildlife, in litt. 1994).
Eggs may be present on the beach from mid-April to late July. Clutch initiation dates have been recorded as early as April 21 in Virginia (Cross 1991), April 15 in New York (C. Brittingham, The Nature Conservancy, pers. comm. 1994), April 20 in Massachusetts (MacIvor 1990), and April 24 in Nova Scotia (Cairns 1977).
Piping plovers generally fledge only a single brood per season, but may renest several times if previous nests are lost or, infrequently, if a brood is lost within several days of hatching (Wrenn 1991, Goldin 1994a, Rimmer 1994). A few extremely rare instances of adults renesting following fledging of an early brood have also been observed (J. Victoria, Connecticut Department of Environmental Protection, in litt. 1994; Bottitta et al. 1994). One female on Cape Cod was observed in five nesting attempts laying a total of 19 eggs in a season (MacIvor 1990). Renests often occur on the same site, but movements between sites have also been recorded (Cross 1990, MacIvor 1990).
A comparison of data from North Carolina (Coutu et al. 1990, McConnaughey et al. 1990, Wrenn 1991), Rhode Island (C. Raithel, files), and Nova Scotia (Cairns 1977), reveals completed clutches from first nest attempts as early as mid-April and as late as mid-June, with a peak in all three areas between April 30 and May 7. Nest initiation appears to be slightly later in Quebec, Prince Edward Island, and on the eastern shore of New Brunswick, with a peak of nest initiation in mid-May to early June (Morse 1982, Tull 1984, Shaffer and Laporte 1992). Although nests may be initiated as late as July 25, few nests hatch after July 15, and the latest recorded hatch date is July 31 in Massachusetts (MacIvor 1990).
Clutch size for an initial nest attempt is usually four eggs, one laid every other day. Eggs are pyriform in shape, with variable buff to greenish ground color marked with black or brown spots. Cairns (1977) and Wilcox (1959) reported mean egg lengths of 32.5 mm (n = 215) and 31.7 mm (n = 26), respectively. Plover nests and eggs are very difficult to detect, especially during the 6-7 day egg-laying phase when the birds generally do not incubate (Goldin 1994a).
Full-time incubation usually begins with the completion of the clutch, averages 27-30 days, and is shared equally by both sexes (Wilcox 1959, Cairns 1977, MacIvor 1990).
Eggs in a clutch usually hatch within four to eight hours of each other, but the hatching period of one or more eggs may be delayed by up to 48 hours (Cairns 1977, Wolcott and Wolcott 1994). Chicks are precocial, often leaving the nest within hours of hatching (Wilcox 1959, Cairns 1982, Wolcott and Wolcott 1994), but are tended by adults who lead the chicks to and from feeding areas, shelter them from harsh weather, and protect the young from perceived predators (see following section). Broods may move hundreds of meters from the nest site during their first week of life (Table 1). Chicks remain together with one or both parents until they fledge (are able to fly) at 25 to 35 days of age. Depending on date of hatching, flightless chicks may be present from mid-May until late August, although most fledge by the end of July (Patterson 1988, Goldin 1990, MacIvor 1990, Howard et al. 1993). After fledging, adults and young may congregate on neutral (non-territorial) feeding grounds prior to southward migration (Cairns 1977).
Most time budget studies reveal that chicks spend a very high proportion of their time feeding (Table 2). Cairns (1977) found that piping plover chicks typically tripled their weight during the first two weeks after hatching; chicks that failed to achieve at least 60% of this weight gain by day 12 were unlikely to survive. Loegering (1992) found that chick weight and length of exposed bill measured at four or five days of age were significantly higher for chicks that ultimately fledged than for those not surviving.
| Source | Location | Data |
|---|---|---|
| Patterson (1988: 40) | Maryland and Virginia | 18 of 38 broods moved to feeding areas more than 100 meters from their nests; 5 broods moved more than 600 meters (distance measured parallel to wrack line). |
| Cross (1989: 23) | Virginia | At three sites, observers relocated broods at mean distances from their nests of 153 m +/-97 m (44 observations, 14 broods), 32 m +/-7 m (8 observations, 3 broods), and 492 m +/-281 m (12 observations, 4 broods). |
| Coutu et al. (1990: 12) | North Carolina | Observations of 11 broods averaged 212 m from their nests; 3 broods moved 400-725 m from nest sites. |
| Strauss (1990: 33) | Massachusetts | 10 chicks moved more than 200 m during first 5 days post-hatch while 19 chicks moved less than 200 meters during same interval. |
| Loegering (1992: 72) | Maryland | Distances broods moved from nests during first 5 days post-hatch averaged 195 m in bay habitat (n=10), 141 m in interior habitat (n=36), and 131 m in ocean habitat (n=41). By 21 days, average movement in each habitat had, respectively, increased to 850 m (n=1), 464 m (n=10), and 187 m (n=69). One brood moved more than 1000 m from its nest. |
| Melvin et al. (1994) | Massachusetts and New York | In 14 incidents in which 18 chicks were killed by vehicles, chicks were run over < 10 m to < 900 m from their nests. In 7 of these instances, mortality occurred > 200 m from the nest. |
| Source | Location | Data |
|---|---|---|
| Flemming (1984: 27) | Nova Scotia | Major chick activities were feeding (80.5% of time) and being brooded (15.7%). Percent of time spent feeding was 34% for chicks ages 0-5 days, and above 89% for all age-classes over 5 days old. |
| Loegering (1992: 74) | Maryland | Chicks 3-10 days old in bay beach, interior, and ocean habitats spent 76%, 80%, and 37% of their time feeding, respectively. Respective time spent foraging by chicks 11-20 days in different habitats were 82%, 88%, and 56%. |
| Elias-Gerken (1994: 51) | New York | On average, chicks spent 73-75% of their time foraging and 13-16% resting. Foraging accounted for 58-73% of time of chicks 0-2 days old, 73-75% for chicks 3-10 days old, 82-77% for chicks 11-20 days old, and 76-75% for chicks 21-25 days old. |
| Goldin (1993b: 44) | New York | In 1988, 61% of chick observations were of feeding, 11% being brooded or guarded, 10% maintenance, 10% locomotion, and 6% disturbance. In 1989, percentages were 59% feeding, 24% maintenance, 7% disturbance, 6% locomotion, and 4% being brooded or guarded. |
| Hoopes (1993: 33) | Massachusetts | Chicks devoted 35% of their time to feeding behaviors, 39% to maintenance, 15% to disturbance-related behaviors, 4% to locomotion, 2% to being brooded, and 5% to other behaviors. |
| Burger (1991: 44) | New Jersey | Chicks spent 22% of their time feeding, 27% alert, 39% running away from people, and 10% crouched. |
| Goldin (1993a: 16) | Rhode Island | Chicks devoted 72% of their time to feeding and 17% to maintenance behaviors; 4% of their time was spent in disturbance behaviors. All other behaviors accounted for 7% of their time. |
Cryptic coloration is a primary defense mechanism for this species; nests, adults, and chicks all blend with their typical beach surroundings. Chicks sometimes respond to vehicles and/or pedestrians by crouching and remaining motionless (Cairns 1977, Tull 1984, Goldin 1993b, Hoopes 1993). Adult piping plovers also respond to intruders (avian and mammalian) in their territories by displaying a variety of distraction behaviors, including squatting, false brooding, running, and feigning injury. Distraction displays may occur at any time during the breeding season, but are most frequent and intense around the time of hatching (Cairns 1977). Distances at which plovers react to human disturbance are summarized in Table 3.
Table 3. Summary of Data on Distances at which Piping Plovers React to
Disturbance
| Source | Location | Data |
|---|---|---|
| FLUSHING OF INCUBATING BIRDS BY PEDESTRIANS: | ||
| Flemming et al. (1988: 326) | Nova Scotia | Adults usually flushed from the nests at distances <40 m; however, great variation existed and reaction distances as great as 210 m were observed. |
| Cross (1990: 47) | Virginia | Mean flushing distances in each of two years were 47 m (n=181, range = 5 m to 300 m) and 25 m (n=214, range = 2 m to 100 m). |
| Loegering (1992: 61) | Maryland | Flushing distances averaged 78 m (n=43); range was 20 m to 174 m. Recommended use of 225 m disturbance buffers on his site. |
| Cross and Terwilliger (1993) | Virginia | Mean flushing distance for all years on all sites (Virginia plover sites, 1986-91) was 63 m (n=201, SD=31, range = 7 m to 200 m). Differences among years were not significant, but differences among sites were. |
| Hoopes (1993: 72) | Massachusetts | Mean flushing distance for incubating plovers was 24 m (n=31). |
| DISTURBANCE TO NON-INCUBATING BIRDS: | ||
| Hoopes (1993: 89) | Massachusetts | Mean response distance (all ages, all behaviors) was 23 m for pedestrian disturbances (range = 10 m to 60 m), 40 m for vehicles (range = 30 m to 70 m), 46 m for dogs/pets (range = 20 m to 100 m), and 85 m for kites (range = 60 m to 120 m). |
| Goldin (1993b: 74) | New York | Average flushing distance for adult and juvenile plovers was 18.7 m for pedestrian disturbances (n=585), 19.5 m for joggers (n=183), and 20.4 m for vehicles (n=111). Pedestrians caused chicks to flush at an average distance of 20.7 m (n=175), joggers at 32.3 m (n=37), and vehicles at 19.3 m (n=7). Tolerance of individual birds varied; one chick moved 260 m in direct response to 20 disturbances in 1 hour. |
Plover foods consist of invertebrates such as marine worms, fly larvae, beetles, crustaceans, and mollusks (Forbush 1925, Bent 1929, Cairns 1977, Nicholls 1989, Gibbs 1986, Shaffer and Laporte 1994). Staine and Burger (1994) found more polychaete worms in core samples taken from intertidal areas where plovers were feeding than in random samples.
Feeding areas include intertidal portions of ocean beaches, washover areas, mudflats, sandflats, wrack lines, and shorelines of coastal ponds, lagoons, or salt marshes (Gibbs 1986, Coutu et al. 1990, Hoopes et al. 1992, Loegering 1992, Goldin 1993b). Studies have shown that the relative importance of various feeding habitat types may vary by site (Gibbs 1986, Coutu et al. 1990, McConnaughey et al. 1990, Loegering 1992, Goldin 1993b, Hoopes 1993, Elias-Gerken 1994) and by stage in the breeding cycle (Cross 1990). Adults and chicks on a given site may use different feeding habitats in varying proportion (Goldin et al. 1990). During courtship, nesting, and brood-rearing, feeding territories are generally contiguous to nesting territories (Cairns 1977), although instances where brood-rearing areas are widely separated from nesting territories are not uncommon (see Table 1). Feeding activities of both adults and chicks may occur during all hours of the day and night (Staine and Burger 1994) and at all stages in the tidal cycle (Goldin 1993b, Hoopes 1993).
Atlantic Coast piping plover migration patterns are not well documented. Most piping plover surveys have focused on breeding or wintering sites, and it is sometimes difficult to distinguish local nesting birds and fledged young feeding on neutral feeding areas from non-local breeders on stopover during southward migration. References to piping plover migration are contained in Bent (1929), Griscom and Snyder (1955), Bull (1964), Cairns (1977), Raithel (1984), Tull (1984), Haig and Oring (1985), Nicholls and Baldassarre (1990a), McConnaughey et al. (1990), Haig and Plissner (1993), and Collazo et al. (1995). Northward migration to the breeding grounds occurs during late February, March and early April, and southward migration to the wintering grounds extends from late July, August, and September. On the breeding grounds, transient birds have been observed following early autumn hurricanes (C. Raithel pers. obs.) and are occasionally sighted during October.
Both spring and fall migration routes are believed to follow a narrow strip along the Atlantic Coast. Appendix B identifies many breeding sites where concentrations of post-breeding and migrating plovers have been observed. There are several North Carolina sites where relatively large numbers of plovers have been observed during migration, including Oregon Inlet, Ocracoke Inlet/Portsmouth Flats, and New Drum Inlet, within the Cape Hatteras and Cape Lookout National Seashores (McConnaughey et al. 1990; S. Wrenn, North Carolina State University, pers. comm. 1994). In addition, plover numbers fluctuate at Ohio Key, Florida during spring and fall periods, suggesting use by migrant plovers (M. Brown pers. comm. 1988).
Sightings away from the outer beaches, either inland or offshore, are rare (Bull 1964, Barbour et al. 1973, Imhof 1975, Potter et al. 1980). Observations of color-marked birds from the Atlantic Coast suggest some crossover to Gulf Coast wintering areas (Haig and Plissner 1993); however, routes are unknown. Occasional sightings of piping plovers at distant islands, such as Bermuda (American Birds 1987, 1990; D. Wingate, Bermuda Aquarium and Natural History Museum, in litt. 1988), demonstrate that long-distance migrations are possible. Intensified survey efforts during migration periods should result in identification of additional important stopover areas.
The piping plover's winter range extends along the Atlantic and Gulf Coasts from North Carolina to Mexico and into the Bahamas and West Indies (USFWS 1985, Haig and Oring 1985, Haig and Oring 1988b, Hoopes et al. 1989). Two fairly comprehensive surveys, one conducted between January 1983 and April 1984 and the other between December 1986 and March 1988, provided preliminary insight into winter distribution and contributed to the identification of specific wintering sites (Haig and Oring 1985, Nicholls and Baldassarre 1990a). The most comprehensive survey to date was the 1991 International Piping Plover Census, which tallied a total of 3,451 plovers, the largest number of birds ever accounted for during the winter period (Haig and Plissner 1993). While approximately 63% of the known adult plovers were observed during this rangewide survey, a large number of plovers are still unaccounted for during the wintering period.
Pooling sightings of banded birds from the 1991 International Census and earlier reports, Haig and Plissner (1993) reported 49 band sightings on the wintering grounds of plovers banded on the Atlantic Coast breeding grounds, including 41 birds (84%) sighted on the southern Atlantic Coast, five (10%) on the Gulf Coast, and three (6%) in the Florida Keys. Twenty-six piping plovers from inland breeding populations (14% of band sightings) were also reported wintering in North or South Carolina. The magnitude of crossover between coasts is difficult to ascertain, because few birds are seen on the Atlantic Coast in winter, and a relatively small proportion of the Atlantic Coast plovers are banded. The development of refined techniques for genetic testing may eventually assist in addressing this issue (S. Haig, National Biological Survey, in litt. 1994).
Plovers wintering on the Atlantic Coast are generally distributed in small groups; six was the average number of piping plovers per site during Nicholls' 1986-87 survey (Nicholls 1989). The barrier islands off Georgia and South Carolina (especially Deveaux Bank) appear to host the largest numbers of wintering birds. A few sites in North Carolina (e.g., Bird Shoals and Figure 8 Island) and Florida (Ward's Bank, Little Talbot Island, Ohio Key, Boca Grande Key) also have relatively high numbers for the Atlantic Coast.
Several sightings have been recorded in the Caribbean and more intensive searches may locate more birds. Haig and Oring (1985) reviewed museum records and did not find any records of birds wintering further south than the Lesser Antilles. Additional searches along the Louisiana, Texas, and Mexico Gulf beaches may result in upward revisions in wintering plover counts there. Indeed, the large proportion of birds found in Louisiana and Texas during the 1991 International Census suggests the possibility that more birds from the Atlantic Coast breeding population may be wintering on the Gulf Coast than previously surmised (Haig and Plissner 1993).
In general, wintering plovers on the Atlantic Coast are found at accreting ends of barrier islands, along sandy peninsulas, and near coastal inlets. Plovers appear to prefer sandflats adjacent to inlets or passes, sandy mudflats along prograding spits, and overwash areas as foraging habitats. These types of substrates may have a richer infauna than the foreshore of high energy beaches and attract large numbers of shorebirds. Roosting plovers are generally found along inlet and adjacent ocean and estuarine shorelines and their associated berms (with wrack and other debris often used as wind-shields), and on nearby exposed tidal flats (Fussell 1990, Nicholls and Baldassarre 1990a).
Nicholls and Baldassarre (1990b) attempted to develop a predictive model of habitat use along the Atlantic and Gulf Coasts and identified variables that could be measured over a broad spectrum of sites. While a few general features, such as the presence of large inlets and large areas of sand or mudflats, appeared important, no single variable dominantly identified typical habitats. Thus, plover distribution may be influenced by a number of habitat variables, and it may be the presence of a diversity of microhabitats in close juxtaposition that separates the sites commonly used by wintering plovers from non-plover sites. While this study provided a preliminary overview of plover winter habitat, more investigation is needed to provide a fuller habitat characterization. Research is presently underway along the Texas Coast to more precisely characterize wintering habitat and to identify features predictive of plover use (Zonick and Ryan 1993). One important discovery from this latter study and the 1991 census was the high use of blue-green algal mats by wintering plovers in the Laguna Madre area. This discovery may broaden the search image for new wintering areas in Mexico and the Caribbean.
Investigations during winter are few and have focused primarily on population density and distribution (Haig and Oring 1985, Haig and Oring 1988b, Nicholls and Baldassarre 1990a, Haig and Plissner 1993). Studies on the Alabama and Texas Coasts have provided insight into habitat use and movements, foraging efficiencies, and interspecific interactions. Johnson and Baldassarre (1988) found that different microhabitats in coastal Alabama -- sandflats, mudflats, beaches -- may serve different functional roles for wintering plovers depending on tidal stage, weather, and time of day. The study also found that plovers spend a high percentage of time foraging relative to other activities during the fall and midwinter. Tidal height appeared to be the most important factor affecting foraging time; higher tide negatively correlated with foraging. Zivojnovich and Baldassarre (1987) radio-tracked several wintering plovers in coastal Alabama and found them to utilize several sites within the general barrier island complex of Mobile Bay depending on tidal stage and weather. Ongoing research on the Texas Coast (Zonick and Ryan 1993) also indicates the importance of tides in plover habitat use.
The periodicity of local tides greatly influences the diurnal availability of foraging habitat (Zonick and Ryan 1993). Habitat along the Atlantic Coast is primarily influenced by lunar tides and is regularly available, thus plover use of sites may be more predictable than in areas such as south Texas where tides are influenced by winds. Indeed, plovers may stay within one inlet area or barrier island complex on the Atlantic Coast (Fussell 1990). Observations of banded birds in Texas suggest that individual plovers shuttle between small, discrete areas from algal or tidal flats to beaches (Zonick and Ryan 1993). Haig and Oring (1985) noted a seasonal difference in habitat use along the Gulf Coast, with larger numbers of plovers occurring on sandflats adjacent to beaches and coastal inlets during the winter; more birds were observed on beaches during migration. Observations along the Texas Coast also suggest this seasonal habitat preference (T. Eubanks, GL/NGP Piping Plover Recovery Team, pers. comm. 1992).
Johnson and Baldassarre (1988) found relatively high site fidelity for plovers wintering in the Mobile Bay area in Alabama. Similarly, there are several reports of banded birds returning year after year to the same wintering sites on both the Atlantic and Gulf Coasts (S. Bogert pers. comm. 1988; T. Below, National Audubon Society, pers. comm. 1988; T. Eubanks pers. comm. 1989; Zonick and Ryan 1993; J. Fussell pers. comm. 1995).
During the winter, piping plovers are often found in association with several other shorebird species (Nicholls and Baldassarre 1990b, Eubanks 1992). Territorial and agonistic interactions have been observed with other piping plovers and similar-sized plover species -- semipalmated and snowy plovers (Johnson and Baldassarre 1988, Zonick and Ryan 1993). In Alabama, combined time spent in territorial and agonistic activities largely involved intraspecific interactions (Johnson and Baldassarre 1988). Piping plovers appear to be aggressive and may defend food patches during the winter period (Zonick and Ryan 1993). Piping plovers also appear to roost in multi-species flocks (Nicholls and Baldassarre 1990b, Zonick and Ryan 1993), but are often found in a tight cluster on the fringes of a flock (J. Nicholls, U.S. Fish and Wildlife Service, pers. obs.).
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Last updated March 15, 2000