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Piping Plovers


by
Susan M. Haig
National Biological Service
Jonathan H. Plissner
University of Georgia

Editor's note: This paper is largely a synopsis of a paper by Haig and Plissner (1993) in Condor.
The piping plover (Charadrius melodus) is a wide-ranging, beach-nesting shorebird whose population viability continues to decline as a result of habitat loss from development and other human disturbance (Haig 1992). In 1985 the species was listed as endangered in the Great Lakes Basin and Canada and threatened in the northern Great Plains and along the U.S. Atlantic coast. The U.S. Fish and Wildlife Service (USFWS) is proposing that birds in the northern Great Plains also be listed as endangered.
Each year, many breeding areas are censused and some winter surveys are conducted. In 1991 biologists from Canada, the United States, Mexico, and various Caribbean nations carried out a simultaneous census of piping plovers at all known breeding and wintering sites. Census goals were to establish baseline population levels for all known piping plover sites and to census additional potential breeding and wintering sites (Figure).

Figure. Distribution of piping plovers throughout the annual cycle in 1991.

Status
This census covered 2,099 sites, resulting in the highest number of breeding and wintering piping plovers ever recorded. It will be repeated three or four more times over the next 15-20 years for more accurate assessment of population trends.

Winter Census
The total number of wintering birds (3,451) reported constituted 63% of the breeding birds (5,486) counted (Tables 1, 2). Most birds (55%; N = 1,898) were found along the Texas coast where the census concentrated on birds in previously uncensused stretches of Laguna Madre's back bays. The highest concentration of birds in local sites was also reported in Texas (Haig and Plissner 1993). Although the 1991 census discovered more wintering birds than had been previously reported, a large proportion of piping plovers were not seen in the winter census. Table 1. Numbers of wintering piping plovers and sites where birds occurred in 1991.  
Location Birds Sites
U.S. Atlantic
 
 
North Carolina 20 7
South Carolina 51 8
Georgia 37 6
Florida 70 9
Total 178 30
U.S. Gulf
 
 
Florida 481 31
Alabama 12 1
Mississippi 59 7
Louisiana 750 23
Texas 1,904 64
Total 3,206 126
Mexico Gulf
27
4
Caribbean
 
 
Bahamas 29 1
Turks and Caicos 0 0
Cuba 11 1
Jamaica 0 0
Puerto Rico 0 0
Cayman Islands 0 0
Total 40 2
Combined total
3,451
162

Better census efforts in Louisiana, northern Cuba, and on many of the smaller Caribbean islands may reveal additional winter sites. Previous reviews of their distribution did not indicate that birds moved farther south than the Caribbean (Haig and Oring 1985). Relatively few birds are seen on the Atlantic coast in winter, a contrast to the 36% of plovers that breed along the Atlantic coast. Thus, the largest gap in our understanding of piping plover distribution during winter appears to be in locating winter sites for Atlantic coast breeders.

Breeding Census
All known piping plover breeding sites were censused in 1991 (Table 2). Piping plovers were widely distributed in small populations across their breeding range (Figure); most adults (63.2%) bred in the northern Great Plains and prairies of the United States and Canada. Thirty-six percent were found on the Atlantic coast and less than 1% occurred on the Great Lakes. Sites with the highest concentrations of breeding birds also were found in the northern Great Plains (also known in Canada as the Great Prairie); however, each local population consisted of only a small (less than 8%) proportion of the total breeding population. Local populations were even smaller on the Atlantic coast. Table 2. Piping plover breeding census, 1991.

Location Adults Sites where piping
plovers occurred
Atlantic Coast
 
 
Canada    
   New; Brunswick 203 24
   Newfoundland; 7 1
   Nova; Scotia 113 34
   Prince; Edward Island 110 20
  Quebec; 76 11
   St.; Pierre/ Miquelon 4 2
Canada Atlantic total 513 92
U.S.    
   Maine; 38 8
   Massachusetts; 293 50
   Rhode; Island 47 7
   Connecticut; 67 7
   New; York 338 69
   New; Jersey 280 22
   Delaware; 10 3
   Maryland; 35 1
   Virginia; 270 14
   North; Carolina 86 14
   South; Carolina 2 1
U.S. Atlantic total 1,466 196
Atlantic total 1,979 288
Great Lakes
 
 
   Duluth;, MN 0 0
   Wisconsin; 1 1
   Michigan; 39 14
   Long; Point, Ontario 0 0
Great Lakes total 40 15
Northern Great Plains/Prairie
 
 
Canada Prairie    
   Alberta; 180 27
   Saskatchewan; 1,172 71
   Manitoba; 80 12
Lake of Woods, Ontario 5 1
Canada Prairie total 1,437 111
U.S. Great Plains    
   Montana; 308 39
   North; Dakota 992 115
   South; Dakota 293 47
   Lake; of Woods, MN 13 1
   Colorado; 13 4
   Nebraska; 398 106
   Iowa; 13 2
   Kansas; 0 0
   Oklahoma; 0 0
U.S. Great Plains total 2,030 314
Combined totals
 
 
   Canada; 1,950 203
   United; States 3,536 525
Total 5,486 728

Migration Areas
Atlantic coast piping plovers are commonly seen on east coast beaches during spring and fall migration. Migration routes of inland birds are poorly understood, however. Only a few occurrences of piping plovers have been reported at seemingly appropriate inland migration sites such as Kirwin National Wildlife Refuge in Kansas, Cheyenne Bottoms Wildlife Management Area in Kansas, and Great Salt Plains National Wildlife Refuge in Oklahoma. It appears that inland birds may fly nonstop to gulf coast sites.

Trends
Because simultaneous, species-wide censuses were not conducted in the past, assessing population trends is difficult. Examination of long-term census data at specific sites is useful in some cases. Most midcontinent sites that have been monitored for 10 years or more have experienced a decline (Table 3). The cumulative effects of problems in the prairies have been modeled, and results indicate that piping plovers in the Great Plains are now declining by 7% annually (Ryan et al. 1993), a devastating trend for the species. Atlantic coast numbers remain stable; however, there has been unprecedented effort to protect piping plovers along the U.S. Atlantic coast. Results from previous censuses (Table 3) should be considered rough population estimates; as is true with many bird species, we have little information regarding the intensity of census efforts in those population estimates. Table 3. Changes in numbers of piping plovers at specific breeding areas.*

Location 1st est. 2nd est. 1991 census % Change 1st est. 1991 % Change 2nd est. 1991
Year
No.
Year
No.
Atlantic Coast
Newfoundland 1968 30 1984 4 7 -72 +75
Cadden Beach, Nova Scotia 1976 56 1983 28 20 -64 -29
Maine 1976 48 1982 12 38 -21 +217
Rhode Island 1945 80 1983 20 47 -41 +135
Connecticut 1980 40 1983 34 67 +68 +97
Long Island, NY 1939 1,000 1983 200 338 -66 +69
New Jersey 1980 118 1983 64 280 +137 +338
Delaware 1978 80 1984 18 10 -88 -44
Maryland 1972 85 1984 25 35 -59 +40
Great Lakes
Michigan 1979 77 1982 14 39 -49 +179
Wisconsin 1900 140 1983 6 1 -99 -83
Northern Great Plains/Prairie
Big Quill Lake, Saskatchewan 1978 210 1984 186 151 -28 -19
Chain Lakes, Alberta 1976 50 n.a. n.a. 9 -72 n.a.
Lake Manitoba, Manitoba 1980 27 1984 9 3 -89 -67
Lake of the Woods, MN 1982 44 1986 32 13 -70 -59
Niobrara River, NE 1978 1981 92 1985 100 110 +20 +10
*Sources are listed in Haig and Oring (1985) and Haig and Plissner (1993).

Threats
In the northern Great Plains, water-level regulation policies on the major rivers (e.g., Platte, Missouri) serve as a direct source of chick mortality and an indirect source of habitat loss through vegetation encroachment and flooding (Schwalbach 1988; Sidle et al. 1992). We know that because 20% of northern Great Plains (Great Prairie) birds use river sites, loss of productivity on rivers such as the Missouri can significantly affect annual productivity for the species. A similar threat to piping plovers occurs on Lake Diefenbaker in Saskatchewan, the largest piping plover breeding site in the world, where each year water levels are raised soon after parents have laid their clutches, resulting in a loss of all nests.
Avian and mammalian predation is a problem throughout the species' breeding range, although population numbers appear to be stabilizing on the Atlantic coast and the Great Lakes as a result of using predator exclosures over nests (Rimmer and Deblinger 1990; Mayer and Ryan 1991; Melvin et al. 1992). Human disturbance continues to be a problem on the Atlantic coast (Strauss 1990), and in the Great Lakes, piping plovers may also be suffering from a lack of viable habitat (Nordstrom 1990). Comparison of food availability at northern Great Plains sites with Great Lakes sites indicated lower diversity and abundance of invertebrates on the Great Lakes. Finally, recent evidence suggests that Great Lakes birds may be suffering from high levels of toxins (i.e., PCB's), which may be a prime factor in low productivity and population growth (USFWS, East Lansing, Michigan, personal communication).
Piping plover (Charadrius melodus). Courtesy S. Haig
The discovery of the high proportion of wintering piping plovers on algal and sand flats has significant implications for future habitat protection. Current development of these areas on Laguna Madre in Texas and Mexico, increased dredging operations, and the continuous threat of oil spills in the Gulf of Mexico will result in serious loss of piping plover wintering habitat.
In summary, piping plovers suffer from many factors that may cause their extinction in the next 50 years. Most devastated are the Great Lakes and northern Great Plains birds whose viability is severely threatened. Unfortunately, recovery is hindered by a lack of knowledge about the winter distribution, status of winter sites, adequate water-management policy in western breeding sites, and direct human disturbance on the Atlantic coast.
For further information:
Susan M. Haig
National Biological Service
Forest and Range Ecosystem Science Center
Oregon State University
3200 SW Jefferson Way
Corvallis, OR 97331
References
Haig, S.M. 1992. The piping plover. Pages 1-18 in A. Poole, P. Stettenheim, and F. Gill, ed. Birds of North America. American Ornithologists' Union, Washington, DC.

Haig, S.M., and L.W. Oring. 1985. Distribution and status of the piping plover throughout the annual cycle. Journal of Field Ornithology 56:334-345.

Haig, S.M., and J.H. Plissner. 1993. Distribution and abundance of piping plovers: results and implications of the 1991 International Census. Condor 95:145-156.

Mayer, P.M., and M.R. Ryan. 1991. Electric fences reduce mammalian predation on piping plover nests and chicks. Wildlife Society Bull. 19:59-62.

Melvin, S.M., L.H. MacIvor, and C.R. Griffin. 1992. Predator exclosures: a technique to reduce predation at piping plover nests. Wildlife Society Bull. 20:143-148.

 Nordstrom, L.H. 1990. Assessment of habitat suitability for reestablishment of piping plovers on the Great Lakes National Seashores. M.S. thesis, University of Missouri, Columbia. 36 pp.

Rimmer, D.W., and R.D. Deblinger. 1990. Use of predator exclosures to protect piping plover nests. Journal of Field Ornithology 61:217-223.

Ryan, M.R., B.G. Root, and P.M. Mayer. 1993. Status of the piping plover in the Great Plains of North America: a demographic simulation model. Conservation Biology 7:581-591.

Schwalbach, M.J. 1988. Conservation of least terns and piping plovers along the Missouri River and its major tributaries in South Dakota. M.S. thesis, South Dakota State University, Brookings. 43 pp.

Sidle, J.G., D.E. Carlson, E.M. Kirsch, and J.J. Dinan. 1992. Flooding: mortality and habitat renewal for least terns and piping plovers. Colonial Waterbirds 15:132-136.

Strauss, E. 1990. Reproductive success, life history patterns, and behavioral variation in a population of piping plovers subjected to human disturbance. Ph.D. dissertation, Tufts University, Boston, MA. 123 pp.


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