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COPYRIGHT 2005 Wilson Ornithological Society
Piping Plover (Charadrius melodus) numbers have declined continentally in the last 50 years, due in part to permanent destruction of breeding and wintering habitats, and reduced reproductive success (Sidle 1984, Haig 1992). This decline has resulted in the Piping Plover being listed as an endangered species in Canada (Haig 1985), endangered in the Great Lakes region of the United States, and threatened elsewhere in the United States (Sidle 1984). Low reproductive success is considered a limiting factor to the recovery of Piping Plovers in the Northern Great Plains (Haig 1992, Ryan et al. 1993, Murphy et al. 1999); however, this aspect of demography has been documented at relatively few alkali lakes (Haig and Plissner 1992, Plissner and Haig 1997, Murphy et al. 1999). Monitoring reproductive success is considered a priority for the recovery of this species (U.S. Fish and Wildlife Service 1994).
Factors thought to affect reproductive success of Piping Plovers include weather (e.g., Grover and Knopf 1982, Haig and Oring 1988, Sidle et al. 1992), fluctuating water levels (e.g., Mayer 1990, Sidle et al. 1992, Espie et al. 1998, Skeel and Duncan 1998), and egg and chick predation (e.g., Rimmer and Deblinger 1990, Mayer and Ryan 1991, Melvin et al. 1992, Mabee and Estelle 2000). The importance of these factors can vary annually and with the type of breeding site (Larson et al. 2002).
Big Quill Lake, Saskatchewan, is a large alkaline wetland and is an important breeding site for Piping Plovers in North America. In 1996, the site had the largest breeding population (435 birds) of any site in North America--8% of the continental population and 26% of the Canadian prairie population (Skeel et al. 1997). However, numbers fluctuate widely from year-to-year: the last three International Censuses at Big Quill Lake reported 151 adults in 1991 (Haig and Plissner 1992), 435 adults in 1996 (Plissner and Haig 1997), and 105 adults in 2001 (Ferland and Haig 2002); Harris and Lamont (1991) reported 43 birds in 1989, and Harris estimated over 440 birds in 1995 (W. C. Harris pers. comm. in Skeel et al. 1997).
Even though Big Quill Lake can support a large breeding population of Piping Plovers, there is very little information on Piping Plover reproductive success at this lake and the role it plays in the overall conservation of this species. The purpose of this paper is to examine the reproductive success of Piping Plovers at Big Quill Lake by documenting nesting chronology, nesting success, and fledging success. Knowledge of Piping Plover reproductive success at such an important breeding area will increase our ability to conserve and manage this endangered species.
METHODS
Study area.--Big Quill Lake (51[degrees] 53'N, 104[degrees] 15' W) is a large (30,700 ha), shallow, saline basin on the Central Saskatchewan Plains about 200 km east of Saskatoon. The shoreline is primarily alkaline mudflats, and is approximately 200 km long when the basin is full. The upper beaches are partially to fully vegetated with alkali grass (Distichlis stricta), western sea-blite (Suaeda depressa), Nuttall's salt-meadow grass (Puccinellia nuttalliana), northern reed grass (Calamagrostis inexpansa), and wild barley (Hordeum jubatum). In 1993 and 1994, the basin was approximately 60% flooded, and beach width was approximately 1,000 m (Harris 1993, 1994). In 1995, the water level in Big Quill increased due to heavy snowfall the previous winter, resulting in a beach width of <200 m (Harris 1995).
Nest surveys.--Our study area was located on the east side of Big Quill Lake and composed approximately one-third of the shoreline. During 1993-1995, we surveyed the study area at least twice weekly from 7 May to 30 August. We searched for territorial pairs of Piping Plovers (birds calling, exhibiting aggressive or defensive behavior, or performing courtship displays) by systematically walking or slowly traversing the shoreline with an all-terrain vehicle (ATV). We watched territorial birds from a distance of 50-100 m, which allowed birds to return to their nest. We plotted the location of all birds on a map of the study area. We marked nests with pin-flags placed at least 30 m away in the adjacent vegetation, and plotted nest locations on an aerial photograph of the shore. We determined nest occupancy using a 15-60x telescope from a distance of 50-100 m during repeat visits. We visited nests every 3 days during initiation and early incubation. Most nests were located...
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