171 SHORT COMMUNICATIONS The Wilson Journal of Ornithology 121(1):171–173, 2009 Accidental Egg Removal by Incubating Piping Plovers Corie L. White, 1,3,4 R. Mark Brigham, 1 and Stephen K. Davis 1,2 ABSTRACT.—Clutch reduction (the disappearance of 1 or more eggs) is often reported in studies exam- ining avian reproductive success and has typically been attributed to nest predation. We recorded clutch reductions at 20 (11%) of 188 Piping Plover (Char- adrius melodus) nests at Chaplin Lake, Saskatchewan from 2002 to 2004. Partial clutch reductions were ini- tially assumed to be the result of predation. However, all egg disappearances at three nests we monitored us- ing video cameras were due to accidental removal by incubating parents. Our observations suggest that ac- cidental removal may occur more frequently than ex- pected in alkaline environments, and are likely mis- classified as losses due to predation. Received 10 De- cember 2007. Accepted 1 July 2008. Estimating demographic rates and identi- fying factors that influence these rates are es- sential for understanding population ecology (Stearns 1992, Miller and Knopf 1993, Lukas et al. 2004), and effectively managing wildlife species (Sarno et al. 1999). A large proportion of applied ornithological research has focused on estimating reproductive success, in partic- ular nest survival (Beauchamp et al. 1996, Knetter et al. 2002, Davis 2003). Critical to this understanding is the correct classification of nest fate. Unfortunately, logistical con- straints often influence nest visitation sched- ules and make accurate assessment of nest fate difficult (Pietz and Granfors 2000). For ex- ample, reduction in clutch size between nest visits is typically attributed to predation, but could result from brood parasitism (Payne 1977), accidental breakage by the nest owners themselves, or by abiotic factors such as strong winds and heavy rains (Sealy 1994). 1 Department of Biology, University of Regina, Re- gina, SK S4S 0A2, Canada. 2 Canadian Wildlife Service, Environment Canada Prairie and Northern Region, Regina, SK S4P 4K1, Canada. 3 Current address: Saskatchewan Watershed Author- ity, 420-2365 Albert Street, Regina, SK S4P 4K1, Can- ada. 4 Corresponding author; e-mail: corie.white@swa.ca Video monitoring has become a relatively common means of studying nesting behavior and allows an accurate assessment of nest fate (Pietz and Granfors 2000, Sanders and Ma- loney 2002, Williams and Wood 2002). We documented the accidental removal of eggs by incubating Piping Plovers (Charadrius melo- dus) breeding at Chaplin Lake, Saskatchewan (50 26 N, 106 40 W) during a study which used video monitoring of nests (White 2005). OBSERVATIONS Chaplin Lake is a large saline lake covering 11,777 ha. The basin is composed of 10 in- terconnected pools used for harvesting brine shrimp (Artemia franciscana) and extraction of sodium sulfate. This lake supports a large nesting population of Piping Plovers with up to 23% of the Saskatchewan population in a given year. Nest searches and monitoring were conducted from early May until mid August in 2002–2004 following Murphy et al. (1999). Nests were checked every 3–5 days to assess hatching success or failure. Four video sys- tems were used during each of the three breeding seasons to monitor nests (n  24 to- tal). Small (29 mm diameter, 74 mm long) re- mote color/infrared cameras (National Elec- tronics Bullet C/IR, B&E Electronics, Regina, SK, Canada) were hidden in artificial ‘‘rocks’’ constructed from hollow wood and placed at randomly selected nests around the lake. The cameras provided color video images during the day and black and white footage at night. Video was continuously recorded (24 hrs) on a time-lapse videocassette recorder (VCR, Sanyo Real Time SRT 2400DC, or Sanyo Real Time 4040AC). We reviewed all video tape records from nests at which egg losses were recorded during nest visits. Clutch size reduction occurred at 10–17% of monitored nests each year (n  188 nests, Table 1). Review of the video (1,946 hrs) at the 3 nests (1 in each year), where video cam- eras were used and which experienced clutch