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Piping Plover (Charadrius melodus circumcinctus)

BACKGROUND

2.1     Description of the Species

Figure 1. Adult Piping Plover.

Figure 1. Adult Piping Plover.

The Piping Plover (Charadrius melodus) is a small (18 cm; 43–63 g) migratory shorebird. It is highly cryptic, with a sand-coloured back and head, white underparts, and orange legs. In breeding plumage (Figure 1), the short bill is orange with a black tip, a single black band stretches between the eyes, and another black band runs across the breast (Haig 1992). The plover is superficially similar in appearance to the Killdeer (Charadrius vociferus), a shorebird that shares habitat with the Piping Plover. The Killdeer, however, is a larger shorebird with a dark brown head and back and two black breast bands. Piping Plovers are characterized by their clear-toned “pipe” call and habit of breeding on open sand or gravel beaches (Goossen et al. 2002).

The Piping Plover is a member of the Charadriidae family (plovers). It is divided into two subspecies: the Atlantic C. m. melodus and the inland C. m. circumcinctus (AOU 1957). The circumcinctus subspecies includes two populations: Prairie Canada and Great Lakes. Both Canadian subspecies are listed as endangered (Boyne 2001) under Schedule 1 of the Species at Risk Act. This recovery strategy applies only to the inland subspecies. Within Canada, C. m. circumcinctus occurs in the provinces of Alberta, Saskatchewan, Manitoba, and Ontario. In the United States, C. m. circumcinctus is threatened in the Northern Great Plains and endangered in the Great Lakes (Sidle 1985), whereas C. m. melodus is listed as threatened on the Atlantic coast.

2.2     General Biology

These predominantly monogamous shorebirds are capable of breeding the first spring after hatch (Haig 1992). They have a modal clutch size of four eggs, with a seven-day laying period (Murphy et al. 1999). Replacement clutches are common due to frequent nest destruction. Double brooding is extremely rare for C. m. circumcinctus but has been observed in the Great Lakes (J. Stucker and C. Haffner, pers. comm., in Haig and Elliott-Smith 2004). Incubation over a 26- to 28-day period is shared by both sexes (Whyte 1985; Haig and Oring 1988b). Both sexes tend broods immediately following hatch, but females may desert broods within 10 days (Haig and Oring 1988b). The precocial young leave the nest within hours after hatching and begin to forage. Frequent brooding (every 5–10 minutes) is required for thermoregulation of young chicks (Haig 1992). Young are capable of sustained flight at 18–25 days (Murphy et al. 1999). Birds may begin migration as early as late June as a result of bad weather and failed nest attempts, although most leave by late July or early August. Peak migration from the wintering grounds is from March (Haig 1992) to April (K. Mehl, pers. comm.), with arrivals on the Canadian prairie breeding grounds occurring from late April to mid-May and in the Great Lakes region of the United States from late April to early May (Pike 1985). C. m. circumcinctus is assumed to be a non-stop migrant, as sightings at appropriate inland stopover sites are rare (Haig 1992). The Great Lakes population may be an exception, as birds have been observed at sites between breeding and wintering areas (U.S. Fish and Wildlife Service 2003).

2.3     Demography

C. m. melodus can live up to 14 years of age (Wilcox 1962); however, few survive beyond the age of nine (Wilcox 1959, 1962). Information on C. m. circumcinctus is limited, but individuals have been known to live up to five years of age (C. Gratto-Trevor, pers. comm.). The estimated mean annual survival rate for adult C. m. circumcinctus, derived from a North Dakota study site, is 0.74 (SE = 0.09), and that for immatures (i.e., fledging to one year of age) is 0.32 (SE = 0.08) (Larson et al. 2000). A Great Lakes study estimated adult survival at 0.73 (Wemmer et al. 2001). Adult breeding site fidelity is highly variable among study sites, but is often high. In five of eight studies, over 50% of adults returned to their former breeding areas (Haig and Oring 1988b). Natal site fidelity is lower than adult breeding site fidelity. Geographical variation in natal site fidelity is evident, with plovers at Lake of the Woods exhibiting the highest natal site fidelity, at 70% (Haig and Oring 1987), and plovers from Nova Scotia exhibiting the lowest, at 1.6% (Cairns 1982). Piping Plover reproductive success, without management and including all habitats used in the Northern Great Plains, is 0.89 chicks fledged per pair (Larson et al. 2002).

2.4     Population and Distribution

2.4.1 Canadian Breeding Distribution

The extant breeding range of C. m. circumcinctus extends from east-central Alberta through southern Saskatchewan and Manitoba to Lake of the Woods in southwestern Ontario (Figure 2). The northernmost known breeding occurrence of the plover is Lake Athabasca, in northern Saskatchewan; however, it is not known if plovers breed regularly there. In southern Ontario, confirmed breeding has not occurred along the shores of the Great Lakes since 1977 (Goossen et al. 2002). Historically, Piping Plovers were likely common residents along shores of the four Great Lakes in Ontario; breeding has been documented on Lake Ontario, Lake Erie, and Lake Huron (Russell 1983).

2.4.2 Wintering Distribution

Although the wintering ranges of the three continental breeding populations of Piping Plovers (Figure 2) overlap, the majority of inland breeders winter along the Gulf of Mexico (Haig and Oring 1988a). Banded Prairie Canada birds have been observed in Mexico, Texas, Alabama, and Florida (Mehl 2003; Stucker et al. 2003; D. Prescott, pers. comm.; Canadian Wildlife Service, unpubl. data). A few have also been seen along the Atlantic coast (Canadian Wildlife Service, unpubl. data). U.S. Great Lakes plovers predominantly winter on the Atlantic coast and Gulf coast of Florida (Haig and Elliott-Smith 2004). Plovers banded in Michigan have been sighted in Alabama, Louisiana, North Carolina, Georgia, Florida, southern Virginia, and the Bahamas (U.S. Fish and Wildlife Service 2003).

2.5     Population Size and Trend

Historically, little is known about the size and distribution of Piping Plover populations in the Canadian Prairies and Great Lakes. Bell (1978), using information from prior to 1978, estimated that there were 10 plovers in Manitoba, 300 in Saskatchewan, and 200–220 in Alberta. In 1985, Haig (1985) estimated 100–120 birds in Manitoba, 700–1200 in Saskatchewan, and 200–220 in Alberta. Estimates from Bell (1978) and Haig (1985) were derived from various sources over various years and were not necessarily complete. Russell (1983) estimated the historical Ontario Great Lakes population at 152–162 pairs.

The first comprehensive survey of Piping Plovers in North America was the international census of 1991 (Haig and Plissner 1992). The 2001 International Piping Plover Breeding Census estimated the North American population at 5945 adults, of which 3025 (51%) were C. m. circumcinctus. Of the 1454 (24%) adult Piping Plovers counted in Canada, 973 (67%) were C. m. circumcinctus, of which 972 were counted in Prairie Canada and one was counted on the Great Lakes in Ontario (Table 1). The entire Northern Great Plains/Prairies population showed a 15% overall population decline between 1991 and 2001 (Haig et al. 2005). The Prairie Canada population experienced a 32% decline from the 1991 (1437) to the 2001 (972) international census and a 42% decline from the 1996 (1687) to the 2001 international census; numbers did, however, increase by 17% between 1991 and 1996. In the United States, there was a slight decline in Great Plains numbers from 1991 to 2001, but numbers increased by about 24% from 1996 to 2001. At Lake of the Woods, in Minnesota and Ontario, numbers declined from 18 adults in 1991 to 13 adults in 1996 to only eight adults in 2001. Declines in this remnant population are troubling, as it serves as the only geographical link between the Northern Great Plains/Prairies and Great Lakes. The American Great Lakes population has more than tripled in the last 15 years, from 40 individuals in 1991 (Haig and Plissner 1993) to ~125 individuals in 2005 (J. Stucker, pers. comm.).

Population trends are difficult to determine due to the ephemeral nature of plover habitat, the large extent of the habitat, the bird’s mobility, and variation in survey efforts and site familiarity of observers. Consideration of U.S. populations is essential to interpret and assess Canadian C. m. circumcinctus population trends.

Figure 2. Breeding and wintering ranges of the Piping Plover (modified from Haig 1992).

Figure 2. Breeding and wintering ranges of the Piping Plover (modified from Haig 1992).
Table 1. Comparisons of the 1991, 1996, and 2001 International Piping Plover

Breeding Censuses in Canada and the United States for C. m. circumcinctus (Haig et al. 2005)

Table 1. Comparisons of the 1991, 1996, and 2001 International Piping Plover Breeding Censuses in Canada and the United States for C. m. circumcinctus (Haig et al. 2005)

2.6     Importance to Humans

Birdwatchers are a major economic factor in ecotourism. Piping Plovers are of interest to birdwatchers, particularly because of their endangered status. Having a high public profile, Piping Plovers contribute to environmental education and highlight endangered species concerns (Goossen et al. 2002).

2.7     Description of Species Needs

Piping Plovers need 1) adequate space for normal behaviour and population growth, including sites for breeding, rearing, feeding, and staging/migration/wintering; 2) a sufficient supply of aquatic and terrestrial invertebrates; 3) little disturbance; and 4) sites relatively secure from predators. The dynamic ecological processes (e.g., water level fluctuations) that create and maintain Piping Plover habitat are essential to ensure the longevity and availability of that habitat.

2.7.1 Ecological Processes

Piping Plover habitat is ephemeral and is characterized by frequent successional disturbances. Precipitation, drought, and water management can significantly influence annual habitat availability. Cycles of alternating high- and low-water years and ice scour are necessary for habitat maintenance, particularly vegetation control on freshwater wetlands. High water levels are effective at removing encroached vegetation resulting from beach exposure during low-water years. Activities such as water level stabilization and management for hydropower disrupt the natural cycle (Hesse and Mestl 1993), which often results in a reduction in habitat availability due to flooding or vegetation encroachment (J.P. Goossen, pers. obs.). Ice scour promotes the maintenance of vegetation-free, early-succession habitat on sand spits and sites near channels (K. De Smet, pers. comm.). The salinity of alkali lakes further inhibits beach vegetation growth (Wershler 1992). Fire and grazing may be other influencing factors (Root and Ryan 2004). On the wintering grounds, hurricanes and tropical storms maintain coastal beach habitats.

2.7.2 Key Habitat Attributes

Piping Plovers prefer open sandy/gravelly beaches, islands, and peninsulas on alkali and freshwater lakes and riverine sandbars. Annual habitat suitability can be unpredictable due to the dynamic nature of the habitat, climate, and hydrological cycles of the Northern Great Plains. The most consistently available plover habitat in the prairies is wide, gravelly shores on permanent, saline water bodies (Wershler and Wallis 1987). The following attributes are typical of habitats where plovers are found, although composition, components, and combinations may vary:

·        beach width >10 m;

·        shoreline length >0.4 km;

·        patches of gravel or sand/gravel;

·        sandbars;

·        distance to tree line from normal high-water mark >50 m;

·        beach with <50% vegetation cover;

·        access to wet, sandy shoreline or seeps, small streams, or interdunal wetlands for feeding;

·        alkali deposits present somewhere on beach (for alkali lakes/wetlands);

·        adjacent upland vegetation from where insect drift occurs; and

·        key ecological processes that create, maintain, or affect habitat, such as weather, including precipitation and drought, wind, groundwater, salinization, water fluctuations, vegetation encroachment or succession, fire, and herbivory.

2.7.3 Nesting Habitat

In Prairie Canada, Piping Plovers choose sand/gravel beaches of permanent to semipermanent alkali lakes and wetlands, freshwater lakes, reservoirs, and occasionally river shorelines and sandbars for nesting and brood rearing (Boyne 2001). In the Great Lakes region of the United States, plovers choose sand spits or sand beaches associated with dunes and swales. Habitat located on the inland side of foredunes is also used for breeding (Pike 1985; Powell and Cuthbert 1992). Piping Plovers prefer to nest on flat, wide, sparsely vegetated sand, gravel, or alkaline substrate (generally not bare alkali) (Haig 1992). Mixed substrates such as sand, gravel, and pebbles are preferred, as they provide camouflage for nests, incubating adults, and young (Boyne 2001). Periodic habitat disturbance such as grazing or flooding is needed, particularly on freshwater lakes, to minimize vegetation encroachment.

2.7.4 Brood Rearing Habitat

Brood-rearing habitat overlaps with nesting and feeding habitats. Often brood habitat is within a pair’s territory; however, families may leave territories because of disturbance or food requirements. Young plovers may use sparse vegetation to provide shelter from the elements or escape from human disturbance or predators. Densely vegetated areas are rarely used by plovers, as these areas are difficult to traverse and limit visibility.

2.7.5 Feeding Habitat

There is little information on the plover’s diet in the Northern Great Plains and Great Lakes (see Whyte 1985; Beckerman 1988; Staine and Burger 1994; Cuthbert et al. 1999). Piping Plovers feed on a variety of aquatic, benthic, and terrestrial invertebrates. Adult Piping Plovers and flightless juveniles feed at seeps, ephemeral river pools, or the river edge (Cuthbert et al. 1999), along the lakeshore, in vegetation, and at the high-water mark within the nesting territory. Non-tending adults and juveniles capable of flight will feed beyond the immediate nesting or brood-rearing area. Birds feed primarily within 5 m of the water’s edge. Time spent at various feeding habitat types varies by sex, age, and stage of breeding (Haig 1992), as well as habitat availability and disturbance.

2.7.6 Staging/Migration Habitat

Piping Plovers stage on natal lakes before migration (Harris 1994). Great Lakes birds use migration habitat on stopovers between breeding and wintering areas (U.S. Fish and Wildlife Service 2003). Sightings at seemingly appropriate inland stopover sites in the Northern Great Plains are rare, suggesting that these birds are non-stop migrants (Haig 1992). Juveniles are capable of covering considerable distances within a few days of attaining flight. Results from a North Dakota study showed that two juveniles covered ≥50 km when 28 days old (Knetter et al. 2001). A colour-banded juvenile migrated >2000 km from North Dakota to the Gulf coast of Mexico in less than five days (M.R. Ryan, unpubl. data, in Knetter et al. 2001). 

2.8     Threats

2.8.1 Predation

Boyne (2001) identified human disturbance as the primary threat to Piping Plovers in Canada; although this may be true for Atlantic Canada, predation appears to be the primary factor limiting Piping Plover productivity on the Northern Great Plains (see Whyte 1985; Haig and Oring 1987, 1988b; Prindiville Gaines and Ryan 1988; Richardson 1999; Westworth et al. 2004). Predation is rarely witnessed, and predator identification is therefore difficult and often inferred from tracks, nest condition, or other evidence. This approach is not always reliable in determining predator identities (Larivière 1999).

The predator complex has changed with the advent of European settlement. The following predator species have increased in numbers since 1966: American Crow (Corvus brachyrhynchos), Black-billed Magpie (Pica hudsonia), California Gull (Larus californicus), Great Horned Owl (Bubo virginianus), Merlin (Falco columbarius), and Ring-billed Gull (Larus delawarensis) in Alberta; Ring-billed Gull and Merlin in Manitoba; and American Crow, Black-billed Magpie, and Merlin in Ontario (Sauer et al. 2003).

Effective mechanisms for predator management have been identified (Schmelzeisen et al. 2004) and will be utilized at various sites where appropriate. The effectiveness of management tools will continually be assessed and refined to reduce predation on eggs, young, and adults.

Egg Predation

Predation of Piping Plover eggs generally involves the whole clutch. The following are confirmed predators of Piping Plover eggs: American Crow (Kruse et al. 2001), Common Raven (Corvus corax) (Schmelzeisen et al. 2004), Black-billed Magpie (Licht and Johnson 1992), American Kestrel (Falco sparverius) (Kruse et al. 2001), mink (Mustela vison) (Kruse et al. 2001), domestic dog (Canis familiaris) (Kruse et al. 2001), and raccoon (Procyon lotor) (Espie et al. 1992; Kruse et al. 2001). The following species are considered potential egg predators based on evidence near the nest or their presence near depredated nests: California Gull (Mayer and Ryan 1991a), blackbirds (Icteridae) (Ivan and Murphy 2005), striped skunk (Mephitis mephitis), American badger (Taxidea taxus) (Casler and Murphy 2001; Murphy et al. 2003a; Ivan and Murphy 2005), coyote (Canis latrans), red fox (Vulpes vulpes) (Goossen et al. 2002; Ivan and Murphy 2005), white-tailed deer (Odocoileus virginianus) (Ivan and Murphy 2005), and ground squirrels (Spermophilus spp.) (Ivan and Murphy 2005).

Chick Predation

Piping Plover chick loss on the Northern Great Plains is considerable, considering that from the average clutch of four eggs, only 0.89 chicks fledge per pair (Larson et al. 2002). Again, predation is rarely witnessed in the field, and chick remains are rarely found. Confirmed predators of chicks are Northern Harriers (Circus cyaneus) (Murphy et al. 2003a; Ivan and Murphy 2005), American Kestrel (Kruse et al. 2001), Great Horned Owl (Kruse et al. 2001), mink (Kruse et al. 2001), and coyote (C. White, unpubl. data; D. Martens, unpubl. data).

Adult Predation

Depredated adults are rarely found. Merlins (Michaud and Prescott 1999) and Peregrine Falcons (Falco peregrinus) (W. Harris, pers. comm., in Goossen et al. 2002) are known predators of plover adults. Potential predators of adult Piping Plovers include coyote, red fox, raccoon, American badger, striped skunk, gulls, Northern Harrier, Great Horned Owl, American Crow, Red-tailed Hawk (Buteo jamaicensis), and Swainson’s Hawk (Buteo swainsoni) (Murphy et al. 2003a). Some plover management activities have attracted raptors, causing adult mortalities (see Murphy et al. 2003a).

Other Predators

Other possible predators of Piping Plovers include Herring Gull (Larus argentatus) (U.S. Fish and Wildlife Service 2003), Short-eared Owl (Asio flammeus) (W. Harris, pers. comm., in Goossen et al. 2002), Snowy Owl (Bubo scandiacus) (Cuthbert and Wemmer 1999), Common Grackle (Quiscalus quiscula) (Ivan and Murphy 2005), and short-tailed weasel (Mustela erminea) (Haig and Elliott-Smith 2004).

2.8.2 Habitat Loss or Degradation

Habitat loss can occur when nesting beaches or basins become unsuitable or unavailable to Piping Plovers through natural causes, such as drought, high precipitation, and vegetation encroachment (Goossen et al. 2002). Human activities, such as water management, recreational development, and oil and gas development, can further contribute to habitat loss (Boyne 2001). The quality of otherwise physically suitable habitat may be compromised by human disturbance, water management, and livestock disturbance. Threats to wintering habitat are also of concern, as plovers spend most of the year on coastal marine habitats.

Mitigation efforts and conservation agreements will address water management threats. Stewardship will be emphasized in future habitat protection. Habitat will be protected through stewardship, legislation, and enforcement. The establishment and enforcement of protected areas, such as at the Walter Cook Piping Plover Conservation Area (Manitoba), the Clandeboye Bay Piping Plover Conservation Area (Manitoba), and the Muriel Lake Waterbird Sanctuary (Alberta), will aid in protecting plover habitat and reproductive efforts.

2.8.3 Livestock Grazing

Livestock may trample nests, disrupt normal breeding behaviour, and alter characteristics of the habitat (Boyne 2001). Feeding habitat quality may deteriorate from cattle urine and manure contamination and trampling (Wershler 1992).

Fencing initiatives, delayed grazing agreements, and alternative watering sites can lessen negative impacts from cattle on Piping Plovers and their habitat (Goossen et al. 2002). If properly managed, cattle can improve habitat for Piping Plovers by reducing vegetation height and density along upper beaches. Landscapes where cattle grazing is the dominant land use may be superior, as they tend to be less fragmented than intensively farmed lands (R. Murphy, pers. comm.).

2.8.4 Human Disturbance

The Piping Plover’s preference for wide sand and gravel beaches on freshwater lakes makes them more susceptible to human impacts. Pedestrians, all-terrain vehicles (ATVs), and other motorized vehicles may inadvertently destroy the highly camouflaged eggs and chicks. Human disturbance can interfere with chick behaviour by decreasing time spent foraging and brooding due to increased vigilance behaviour (Flemming et al. 1988).

Stewardship, education, and enforcement will address the threat of human disturbance. Educational materials, such as pamphlets, brochures, and web sites, will help increase public awareness, appreciation, and concern for the Piping Plover and its habitat. Parking lots, vehicle barriers, and signs identifying breeding beaches will also help to minimize human disturbance by reducing beach access. Guardian programs can be used to increase public awareness (see Dufour 2003; Jacobson 2003; Maconachie 2003). In some instances, increased enforcement may be required to protect Piping Plovers and their habitat.

2.8.5 Mortality on Wintering Grounds

Little is known about the survival of Piping Plovers on the wintering grounds. The only study conducted found no mortality among 49 radio-marked plovers in Texas, suggesting that winter mortality may not be a major factor contributing to population declines (Drake et al. 2001).

2.8.6 Other

Other potential threats include West Nile virus (C. Kruse, pers comm.), weather (Smith and Heilhecker 1995; Harris et al. 2005), and pollution, including oil. Concentrations of polychlorinated biphenyls (PCBs) found in plover eggs collected in Michigan have the potential to cause reproductive impairment (D. Best, pers. comm., in U.S. Fish and Wildlife Service 2003). The magnitude of these threats to the Piping Plover and its habitat is unknown.

2.9     Actions Already Completed or Under Way

In 1989, the first recovery plan (unpublished) for both subspecies was completed (Atlantic and Prairie Piping Plover Recovery Teams 1989) and provided direction for the early years of recovery activities. Later, under the Recovery of Nationally Endangered Wildlife (RENEW) program, a second plan was developed and then published in 2002 (Goossen et al. 2002). COSEWIC approved separate listings for the two plover subspecies in 2001; with the passing of the Species at Risk Act in 2002, separate recovery strategies were prepared for each subspecies (this strategy and Environment Canada in prep.). Recovery of circumcinctus in Prairie Canada has benefited from federal–provincial–non-government agency cooperation and international cooperation with the United States and Mexico.

To date, recovery actions for the Great Plains Piping Plover have focused on monitoring (annual lake censuses, four international censuses) (Haig and Plissner 1993; Plissner and Haig 2000; Schmelzeisen and Engley 2003; Haig et al. 2005), productivity enhancement (predator exclosures, clutch translocation, nest enclosures, water management) (Richardson 1997; Engley et al. 2004; Harris et al. 2005), habitat management (Saskatchewan Watershed Authority 2004), research (habitat, population dynamics, and dispersal) (Espie 1994; Dundas 1995; White 2005), and communication (guardian programs, brochures, presentations, science workshop) (Dufour 2003; Westworth et al. 2004; Jacobson 2005).

2.10     Knowledge Gaps

The following lists, compiled from input by researchers at a recent Piping Plover workshop (see Westworth et al. 2004), identify and rank knowledge gaps in decreasing order of importance. Greater knowledge in these areas will benefit provincial, national, and international conservation efforts.

2.10.1 Research Knowledge Gaps

1.     Accuracy of fledging rate estimates.                                                                                   

2.     Standardize terminology (e.g., fledging success, pairs).                                                       

3.     Movements of adults and young between areas.                                                                 

4.     Juvenile survival.

5.     Detectability rate during International Piping Plover Censuses in different areas.                   

6.     Role of various predators and predator ecology.                                                                

7.     Landscape analysis related to plover productivity.                                                              

8.     Wintering ground locations, detectability, and threats.                                                         

9.      Demographics of dispersing adults.                                                                                   

10.  Water regime effect on distribution and influence on census results.                                    

11.  Staging and migration.

In addition to the above, information is also lacking or limited on the role of food in habitat selection and plover management (E. Nol, pers. comm.), the amount of habitat and spatial distribution needed to reach the recovery goal, and the relationship, if any, between habitat quality and predator populations. There is also a need to revisit population models for this species.

2.10.2 Management Knowledge Gaps

1.       Livestock impacts on plover habitats and productivity.

2.       Influence of vegetation encroachment on plover site selection and productivity.

3.       Recreational impacts on plover habitat and productivity.