While hunting is thought to have been a major factor contributing to the decline of the piping plover in the late 19th and 20th centuries, shooting of the piping plover and other migratory birds has been prohibited since 1918 pursuant to the provisions of the Migratory Bird Treaty Act. Habitat loss and degradation, disturbance by humans and pets, and increased predation were cited as important causes of the downward trend that started in the late 1940's (USFWS 1985) and continues to the present time in some portions of the Atlantic Coast.
The wide, flat, sparsely vegetated barrier beaches preferred by the piping plover are an unstable habitat, dependent on natural forces for renewal and susceptible to degradation by development and shoreline stabilization efforts.
Destruction of beach habitat by residential, resort, and seawall development constitutes irrevocable habitat loss for piping plovers. The Coastal Barriers Task Force (1983) states:
In Maine, construction of seawalls, jetties, piers, homes, parking lots, and other structures has reduced historic nesting habitat by more than 70%; where more than 20 miles of historic habitat may have supported more than 200 pairs of piping plovers (Maine Department of Inland Fisheries and Wildlife 1994), 32 pairs nested in 1993 on habitat with an estimated capacity of 52 pairs (M. McCollough, Maine Department of Inland Fisheries and Wildlife, in litt. 1994). Wilcox (1959) pointed to summer home and road construction as causes of declining plover nesting along Moriches Bay on Long Island, New York between 1939 and 1951. Raithel (1984) cited coastal development and shoreline stabilization, including construction and dredging of permanent breachways, building of breakwaters, and planting of dune areas as major contributors to the decline of the piping plover in Rhode Island. Creation of a parking lot in the early 1980's is cited by C. Raithel (in litt. 1994) as reducing habitat at East Matunuck State Beach, "formerly one of Rhode Island's largest Least Tern and Piping Plover sites," an area that he now estimates can provide habitat for only three pairs of plovers. Analysis of four years of piping plover nest location data on a New York site found that the nests were significantly farther from concrete walkways leading from the dunes to the berm than were random points, suggesting that the walkways decrease the carrying capacity of the beach (Hoopes 1995).
The location of developments on beaches where they are vulnerable to erosion often leads to impacts that go far beyond the footprint of the facilities themselves. Requests from private communities within the Fire Island National Seashore, New York, to construct artificial dunes on adjacent undeveloped National Park Service lands in 1993 (NPS 1993a) exemplify situations where shoreline development has created demand to stabilize adjacent habitat.
The magnitude of impacts of development and shoreline stabilization on availability of piping plover habitat in Atlantic Canada is unclear. Austin-Smith et al. (in CWS 1994) "suspect that the intentional stabilization of beaches at some traditional breeding sites has led to decreased incidence of overwashes and blowout, thus reducing favored habitat for nesting plovers" in Nova Scotia. On the other hand, Chaisson et al. (in CWS 1994) state that "human-induced habitat change is a relatively minor concern in the coastal dune system" of northeastern New Brunswick.
Impacts of shoreline developments are often greatly expanded by the attendant concerns for protecting access roads. For example, much of Hatteras Island in North Carolina remains "undeveloped," but approximately 56 miles of continuous dune line is maintained to protect State Highway 12, which runs the length of the island, through Cape Hatteras National Seashore and Pea Island National Wildlife Refuge. Piping plovers nest only on the roadless spits at Cape Point and Hatteras Inlet (Coutu et al. 1990), no longer nesting on Pea Island, where they once occurred (Cairns and McLaren 1980). On unroaded Cape Lookout National Seashore, by contrast, piping plover nesting areas in 1990 included not only the spits at the current inlets, but several former inlets and large moist sand flats (McConnaughey et al. 1990). Biologists believe that dune maintenance conducted to protect more than eight miles of access road is one of several factors contributing to very low density of piping plovers at Island Beach State Park in New Jersey (C.D. Jenkins pers. comm. 1993). Almost five miles of beach habitat in Duxbury and Plymouth, Massachusetts, are affected by dune stabilization to protect over-land access to 290 homes located on upland habitat at the end of the peninsula (C. Wasserloos, Federal Emergency Management Agency, in litt. 1993).
Jetties and groins may cause significant habitat degradation by robbing sand from the down-drift shoreline. For example, the Coastal Barriers Study Group (1987) and the Ocean City, Maryland and Vicinity Water Resources Study Reconnaissance Report (U.S. Army Corps of Engineers 1994) attribute the accelerated, landward shoreline recession of the north end of Assateague Island in Maryland (the only remaining piping plover breeding area in that State) to cumulative effects on the natural drift system from inlet stabilization and nourishment of the rapidly eroding beaches at Ocean City. Loss of sand down-drift of a jetty or groin may be partially off-set by habitat accretion on the up-drift side of a structure. Breezy Point at the western end of southern Long Island, New York serves as a striking example of concentrated piping plover numbers on the accreting side of a jetty (A. Hecht, U.S. Fish and Wildlife Service, pers. obs.). However, beaches on the accreting side of jetties may also be subject to plant succession that makes them less attractive to piping plovers over time.
Wilcox (1959) described the effects on piping plovers from catastrophic storms in 1931 and 1938 that breached the Long Island barrier islands, forming Moriches and Shinnecock Inlets and leveling dunes. Only 3-4 pairs of piping plovers nested on 17 miles of barrier beach along Moriches and Shinnecock Bays in 1929; however, following the creation of Moriches Inlet in 1931, plover numbers increased to 20 pairs along a two mile stretch of beach by 1938. Wilcox added that Moriches Inlet moved one mile west between 1931 and 1956. In 1938, a hurricane opened Shinnecock Inlet and also flattened dunes along both Bays. In 1941, plover numbers along the same 17-mile stretch of beach peaked at 64 pairs. Numbers then gradually decreased, a decline that Wilcox attributed to deposition of dredged sand to rebuild dunes, planting of beach grass, and construction of roads and summer homes. Analysis of aerial photographs of Fire Island, immediately west of Wilcox' study area, by Leatherman and Allen (1985), showed that during the same time period as Wilcox' study, coverage of Fire Island by overwash declined from 26% in 1938 to 11% in 1954 and 2% in 1960.
A study of nest site selection on the central barrier islands of southern Long Island, New York (Elias-Gerken 1994) found that beach segments where piping plover broods had access to ephemeral pools or bayside foraging areas were strongly selected by nesting plovers. The creation of a new inlet and a large overwash zone in Elias-Gerken's study area by a December 1992 storm coincided with colonization of these areas by nesting plovers the following season. On beaches without ephemeral pools or access to bayside mudflats, the probability of plover nesting increased with increasing width of "open vegetation," which she characterized as a "storm-maintained, early successional habitat."
Habitat availability for nest site selection is decreased where blowouts or gaps in the foredune are "plugged," increasing the foredune slope. An investigation into effects of foredune slope on nest site selection by piping plovers was conducted by Strauss (1990), using collected data on nest sites of piping plovers at Sandy Neck in Barnstable County, Massachusetts from 1984-87. Strauss' study area included a flat, sparsely vegetated sandspit, steep mature vegetated foredunes, and blowouts or gaps in the foredune caused by wind or wave action. Although mature foredunes, including many areas where former or incipient blowouts had been deliberately plugged with discarded Christmas trees and/or snowfence, constituted 83% of the beachfront, none of 80 plover nest attempts occurred seaward of the steep foredunes. Furthermore, foredune profiles of blowout (n=26) and sandspit nests (n=34) were significantly less steep than those of 40 random profiles.
On some beaches, artificial or stabilized dunes and vegetation may also impair piping plover nest site selection and/or chick survival by blocking access to bayside feeding areas. Loegering and Fraser (1995) found that flightless plover chicks on Assateague Island, Maryland that were able to reach bay beaches and the island interior had significantly higher survival rates than those that foraged solely on the ocean beaches. Their management recommendations stressed the importance of sparsely vegetated access routes to bayside beaches maintained by overwash (see footnote 2, page 6). Overwash was also cited as an important component of interior habitat maintenance, and Loegering and Fraser expressly discouraged deposition of dredged material and artificial dune building. Piping plover broods on some portions of the barrier beach on Chappaquiddick Island, Martha's Vineyard, Massachusetts, have been observed walking across a gently sloped barrier beach from ocean to bayside feeding areas with the turning of almost every tide (T. Chase, The Trustees of Reservations, pers. comm. 1992), and concern has been expressed that installation of snowfences to build dunes on this beach will degrade piping plover and least tern habitat (P. Huckery, Massachusetts Division of Fisheries and Wildlife, in litt. 1994).
The increasing intensity of human recreation dating from the end of World War II on Atlantic Coast piping plover breeding sites was a major threat cited in the 1986 listing of the piping plover. The Coastal Barriers Task Force (1983) states, "In the thirty-five years following World War II, many factors have combined to produce an explosion in the demand for the kinds of recreational opportunities that coastal barriers provide." Factors contributing to this "explosion" include a 47% growth in the populations of the 19 states bordering the Atlantic Ocean and Gulf Coast between 1950 and 1980; increasing affluence and leisure time; increasing use of motor vehicles, bringing coastal barriers within easy access to more people; and an increasing diversity of recreational demands. Many examples serve to illustrate the role of beach recreation in the post-1950 decline of the piping plover and the need to continue and (in some locations) intensify efforts to protect piping plovers from human disturbance:
Few vehicles were observed in 1950 at Sandy Neck, in Barnstable, Massachusetts. By 1981, 2,234 permits were given for ORV's at this same beach; in 1989, 4,000 ORV permits were issued (Blodget 1990). Between 1984 and 1989, the piping plover population on the same beach declined from 14 pairs to five pairs, and productivity between 1984 and 1988 was extremely low (0.33 chicks per pair), although it improved substantially after the core of the nesting area was closed to vehicles starting in 1989 (Strauss 1990; E. Strauss, University of Massachusetts, Boston, pers. comm. 1991). Further vehicle restrictions to prevent crushing of nests and chicks were instituted in 1990, and the population increased to 18 pairs with a productivity of 2.1 chicks per pair by 1994 (S.M. Melvin in litt. 1994).
Visitation to Cape Cod National Seashore (CACO) increased from 2,830,000 visits in 1966 to 4,979,000 visits in 1981; during that same period, annual visits to Cape Hatteras National Seashore (CAHA) increased from 1,133,000 to 1,635,000 (Coastal Barriers Task Force 1983). By 1987-1993, average annual visitation at CAHA had increased to 2,125,000 (D. Avrin, National Park Service, pers. comm. 1994). Another National Seashore, Fire Island, saw an increase in average annual visitation from 449,000 visits in 1967-1976 to 815,000 visits in 1988-1993 (D. Avrin pers. comm. 1994).
Cape Henlopen State Park in Delaware was first opened to off-road vehicle use in 1978 (Delaware Department of Natural Resources and Environmental Control 1993). Piping plover counts on that site dropped from eight (adults) in 1979 (J. Thomas in litt. 1986) to none in 1988. In 1990, Delaware State Parks implemented restrictions on vehicles in the vicinity of plovers, and there are now tenuous signs that plovers may reestablish at Cape Henlopen (L. Gelvin-Innvaer, Delaware Division of Fish and Wildlife, in litt. 1994).
Vehicle use is prohibited on all beaches in New Brunswick (R. Chaisson, Atlantic Piping Plover Working Group, in litt. 1993) and Prince Edward Island (McAskill et al. in CWS 1994) and on Province-owned beaches in Nova Scotia. However, remote locations of many small nesting beaches makes enforcement extremely difficult, and plover censusers frequently report vehicles and tire tracks on beaches (Boates et al. 1994, CWS 1994, S. von Oettingen pers. comm. 1994).
Various management techniques, including fencing and posting of nesting sites and the exclusion of vehicles from areas where chicks are present, can mitigate impacts of beach recreation on piping plovers, but must be implemented annually as long as the demand for beach recreation continues.
Non-motorized recreational activities can be a source of both direct mortality and harassment of piping plovers. Pedestrians on beaches may crush eggs (Burger 1987b, Hill 1988, Shaffer and Laporte 1992, CACO 1993, Collazo et al. 1994). Unleashed dogs may chase plovers (McConnaughey et al. 1990), destroy nests (Hoopes et al. 1992), and kill chicks (Cairns and McLaren 1980; Z. Boyagian, Massachusetts Audubon Society, pers. comm. 1994).
Concentrations of pedestrians may deter piping plovers from using otherwise suitable habitat. Ninety-five percent of Massachusetts plovers (n = 209) observed by Hoopes (1993) were found in areas that contained less than one person per 8100 m2 of beach. Elias-Gerken (1994) found that piping plovers on Jones Beach Island, New York, selected beachfront that had less pedestrian disturbance than beachfront where plovers did not nest. Sections of beach at Trustom Pond National Wildlife Refuge in Rhode Island were colonized by piping plovers within two seasons of their closure to heavy pedestrian recreation (C. Blair and J. Kurth, U.S. Fish and Wildlife Service, pers. comm. 1988 and 1990, respectively). Burger (1991, 1994) found that presence of people at several New Jersey sites caused plovers to shift their habitat use away from the ocean front to interior and bayside habitats; the time plovers devoted to foraging decreased and the time spent alert increased when more people were present. Burger (1991) also found that when plover chicks and adults were exposed to the same number of people, the chicks spent less time foraging and more time crouching, running away from people, and being alert than did the adults.
Pedestrians may flush incubating plovers from nests (see Table 3, page 12), exposing eggs to avian predators or excessive temperatures. Repeated exposure of shorebird eggs on hot days may cause overheating, killing the embryos (Bergstrom 1991); excessive cooling may kill embryos or retard their development, delaying hatching dates (Welty 1982). Pedestrians can also displace unfledged chicks (Strauss 1990, Burger 1991, Hoopes et al. 1992, Loegering 1992, Goldin 1993b), forcing them out of preferred habitats, decreasing available foraging time, and causing expenditure of energy.
Fireworks are highly disturbing to piping plovers (Howard et al. 1993). Plovers are also intolerant of kites, particularly as compared to pedestrians, dogs, and vehicles; biologists believe this may be because plovers perceive kites as potential avian predators (Hoopes et al. 1992).
Unrestricted use of motorized vehicles on beaches is a serious threat to piping plovers and their habitats. The magnitude of these threats is particularly significant because vehicles extend impacts to remote stretches of beach where human disturbance would be very slight if access were limited to pedestrians. For example, approximately 0.5 mile of life-guarded beach at Race Point Beach on the Cape Cod National Seashore received an average of 334,000 visits in 1989 and 1990 (I. Tubbs, National Park Service, pers. comm. 1990). In 1989, CACO also sold 2,338 season ORV permits and 290 permits for self-contained camping vehicles; ORV permittees (most of whom made multiple trips on their permits) extend impacts to an additional 8.1 miles of beach that receive only light use by pedestrians walking beyond the 0.5 miles of life-guarded beach (K. Jones, National Park Service, pers. comm. 1991).
Vehicles can crush eggs (Wilcox 1959; Tull 1984; Burger 1987b; Patterson et al. 1991; United States of America v. Breezy Point Cooperative, Inc., U.S. District Court, Eastern District of New York, Civil Action No. CV-90-2542, 1991; Shaffer and Laporte 1992) as well as adults and chicks. In Massachusetts and New York, biologists documented 14 incidents in which 18 chicks and two adults were killed by vehicles between 1989 and 1993 (Melvin et al. 1994). Goldin (1993b) compiled records of 34 chick mortalities (30 on the Atlantic Coast and four on the Northern Great Plains) due to vehicles. Biologists that monitor and manage piping plovers believe that many more chicks are killed by vehicles than are found and reported (Melvin et al. 1994). Beaches used by vehicles during nesting and brood-rearing periods generally have fewer breeding plovers than available nesting and feeding habitat can support. In contrast, plover abundance and productivity has increased on beaches where vehicle restrictions during chick-rearing periods have been combined with protection of nests from predators (Goldin 1993b, S.M. Melvin pers. obs.).
Typical behaviors of piping plover chicks increase their vulnerability to vehicles. Chicks frequently move between the upper berm or foredune and feeding habitats in the wrack line and intertidal zone. These movements place chicks in the paths of vehicles driving along the berm or through the intertidal zone. Chicks stand in, walk, and run along tire ruts, and sometimes have difficulty crossing deep ruts or climbing out of them (Eddings et al. 1990, Strauss 1990, Howard et al. 1993). Chicks sometimes stand motionless or crouch as vehicles pass by, or do not move quickly enough to get out of the way (Tull 1984, Hoopes et al. 1992, Goldin 1993b). Wire fencing placed around nests to deter predators (Rimmer and Deblinger 1990, Melvin et al. 1992) is ineffective in protecting chicks from vehicles because chicks typically leave the nest within a day after hatching and move extensively along the beach to feed (see Table 1, page 9).
Vehicles also significantly degrade piping plover habitat or disrupt normal behavior patterns. They may harm or harass plovers by crushing wrack into the sand and making it unavailable as cover or a foraging substrate (Hoopes et al. 1992, Goldin 1993b), by creating ruts that can trap or impede movements of chicks (J. Jacobs, U. S. Fish and Wildlife Service, in litt. 1988), and by preventing plovers from using habitat that is otherwise suitable (MacIvor 1990, Strauss 1990, Hoopes et al. 1992, Goldin 1993b, Hoopes 1994). Vehicles that drive too close to the toe of the dune may destroy "open vegetation" that may also furnish important piping plover habitat (Elias-Gerken 1994).
While removal of human-created trash on the beach is desirable to reduce predation threats, the indiscriminate nature of mechanized beach-cleaning adversely affects piping plovers and their habitat. In addition to the danger of direct crushing of piping plover nests and chicks and the prolonged disturbance from the machine's noise, this method of beach-cleaning removes the birds' natural wrackline feeding habitat (Eddings and Melvin 1991, Howard et al. 1993).
Predation has been identified as a major factor limiting piping plover reproductive success at many Atlantic Coast sites (Burger 1987a, MacIvor 1990, Patterson et al. 1991, Cross 1991, Elias-Gerken 1994). As with other limiting factors, the nature and severity of predation is highly site-specific. Predators of piping plover eggs and chicks include red fox, striped skunk, raccoon, Norway rat, opossum, crows, ravens, gulls, common grackles, American kestrel, domestic and feral dogs and cats, and ghost crabs.
Substantial evidence exists that human activities are affecting types, numbers, and activity patterns of predators, thereby exacerbating natural predation. Non-native species such as feral cats and Norway rats are considered significant predators on some sites (Goldin et al. 1990, Post 1991; see also Appendix C). At other locations, the introduction of predator species to islands has resulted in increased predation pressure on piping plovers and their young. For example, skunks have been introduced to Martha's Vineyard in Massachusetts (T. French, Massachusetts Division of Fish and Wildlife, pers. comm. 1989). Humans have also indirectly influenced predator populations. Human activities have abetted the expansions in the populations and/or range of other species such as gulls (Erwin 1979, Drury 1973) and opossum (Gardner 1982). The availability of trash at summer beach homes increases local populations of skunks and raccoons (Raithel 1984). Strauss (1990) found that the density of fox tracks on a beach area was higher during periods of more intensive human use.
In addition to direct predation on piping plovers, herring, great black-backed, and ring-billed gulls compete with plovers for space and may cause piping plovers to abandon former nesting areas. Raithel (1984) noted that piping plovers no longer nest on the northern tip of Block Island, Rhode Island, where a large gull colony now occurs. Nesting pairs of piping plovers declined at Monomoy National Wildlife Refuge in Massachusetts as a large gull colony grew rapidly during the 1960's and 70's (USFWS 1988c). Cross (1988) attributed the absence of breeding plovers on South Metompkin Island (contrasted with 30 and five pairs, respectively, on islands immediately to the north and south) to intimidation and nest site competition from 2,000+ pairs of herring gulls. Cartar (1976) suggested that invading gulls were a major factor in plover nest destruction at Long Point, Ontario. The U.S. Fish and Wildlife Service believes that nesting gulls pose a substantial threat to piping plovers and other nesting shorebirds at Breezy Point, New York and has encouraged the National Park Service to eliminate the gull colony (N. Kaufman and P. Nickerson, U.S. Fish and Wildlife Service, in litt. 1992 and 1994, respectively).
Increased depredation by crows may be an indirect adverse impact of woody vegetation plantings. Elias-Gerken (1994) observed these avian predators perching and nesting in exotic Japanese black pines along the Ocean Parkway on Jones Island, New York, and hypothesized that this vegetation and other artificial perches exacerbated depredation by crows there.
Migrating peregrine falcons are transitory inhabitants of most Atlantic Coast plover breeding sites (and nest on a few artificial sites in Virginia, Maryland, and New Jersey) and are incidental predators of piping plovers. In response to recovery efforts for that species, peregrine numbers are now increasing. Incidence of piping plover depredation by peregrines may be increasing relative to the 1950's and 1960's when the latter species' numbers were very depressed, but even at full recovery levels there is no reason to believe that peregrines will become a significant piping plover predator (P. Nickerson pers. comm. 1994).
Overall winter habitat loss is difficult to document, but some historical accounts indicate that degradation has occurred along the Atlantic Coast (Stevenson 1960). A variety of anthropogenic disturbance factors has been noted that may affect plover survival or utilization of wintering habitat (Nicholls and Baldassarre 1990a, Haig and Plissner 1993). These factors include recreational activities (motorized and pedestrian), inlet and shoreline stabilization, dredging of inlets, beach maintenance and renourishment, and pollution (e.g., oil spills) (Nicholls and Baldassarre 1990a, Haig and Oring 1985, Haig and Plissner 1993).
Wintering habitat, like Atlantic Coast breeding habitat, is dependent on natural forces of creation and renewal. Man-made structures along the shoreline or manipulation of natural inlets can upset this dynamic process and result in habitat loss or degradation (Melvin et al. 1991). For example, dredging of inlets can affect spit formation adjacent to inlets, while jetties can cause widening of islands and subsequent growth of vegetation on inlet shores. Over time, both result in loss of plover habitat. Additional investigation is warranted to determine the extent to which these disturbance factors affect wintering plovers (Melvin et al. 1991). This is a particularly pressing problem in Texas because of several major U.S. Army Corps of Engineers projects with the potential to impact plover wintering habitat (Haig and Plissner 1993).
Nicholls (1989) found higher densities of both people and off-road vehicles on wintering sites without piping plovers than those where they were present. Although these differences were not statistically significant, she cited the need for further investigation of recreational impacts on wintering plovers (J. Nicholls in litt. 1989).
Severe cold weather and storms are believed to take their toll on wintering plovers. After an intense snowstorm swept the entire North Carolina Coast in late December 1989, high mortality of many coastal bird species was noted (Fussell 1990). Piping plover numbers decreased significantly from approximately 30-40 to 15 birds. While no dead piping plovers were found, circumstantial evidence suggests that much of the decrease was mortality (Fussell 1990). Hurricanes may also result in direct mortality or habitat loss, and if piping plover numbers are low enough or if total remaining habitat is very sparse relative to historical levels, population responses may be impaired even through short-term habitat losses. Wilkinson and Spinks (1994) suggest that, in addition to the unusually harsh December 1989 weather, low plover numbers seen in South Carolina in January 1990 (11 birds, compared with more than 50 during the same time period in 1991-1993) may have been influenced by effects on habitat and food availability caused by Hurricane Hugo which came ashore there in September 1989. Hurricane Elena struck the Alabama Coast in September 1985 and subsequent surveys noted a reduction of foraging intertidal habitat on Dauphin and Little Dauphin Islands (Johnson and Baldassarre 1988). Birds were observed foraging at Sand Island, a site that was previously little used prior to the hurricane.
Oil spills pose a threat to piping plovers throughout their life cycle. Oiled plovers have been reported from Breezy Point, New York; Sandy Hook and Mantoloking, New Jersey; Trustom Pond, Rhode Island; Horseneck Beach, Massachusetts; and Matagorda Island National Wildlife Refuge, Texas (USFWS files).
Fourteen abandoned plover eggs from five New Jersey sites were analyzed for presence of organochlorine and heavy metal burdens in 1990 (USFWS 1991a). Although DDE, PCB's, and chlordane metabolites were detected in all samples, levels did not appear to threaten reproduction. Mercury concentrations ranged from 0.077 to 1.07 ppm wet weight; with the exception of 1.07 ppm wet weight mercury in eggs from Brick Township, New Jersey, mercury residues in that study appeared below those thought causative of avian reproductive anomalies.
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Last updated March 15, 2000