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Haig, S. and L.W. Oring. 1986. Population evaluation of piping plovers at Lake of the Woods, Minnesota. Report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. Unpaged.


Since 1982, Piping Plovers have been studied at 5-6 sites at LOTW (Wiens 1986, Oring and Haig 1985). Initial work concentrated on collection of individual life history data, while research carried out during the past 2 years has focused on monitoring the population as a whole. Information presented in this report utilize data from 1982-1985 to gain perspective on results from 1986. Field trips were carried out from May 14-17, June 5-8, July 3-6, and July 15-18, 1986. During each visit, Piping Plovers were censused at Zippel Bay, Morris Point, Pine Island, Curry Island, and Oak Point. Factors influencing mortality and reproductive success were monitored. In 1986, 84-87% of the Piping Plovers at LOTW had hatched or previously bred on the study sites. High return rates indicate a low recruitment of individuals from outside the area into the population. It is noteworthy that five of six adults banded as new breeders in 1985 were present again in 1986. 20% of 1985 chicks (n=10) returned to breed. The 1986 population at LOTW consisted of 11 breeding pairs, 9-10 transients, and 14 chicks. In addition, at least 1 bird was seen at Rocky Point. This estimate of 31-32 birds represents an 11-24% decrease from the 1985 population (Oring and Haig 1985). Pair counts from previous breeding seasons indicate the number of pairs present in 1986 is approximately 50% less than pair counts for 1983-1985. The largest decrease was found on Pine Island. Nine chicks fledged from Pine Island representing an average fledging rate of 0.8 chicks per pair. The factors responsible for poor nest and/or brood success are varied, including summer storms, mink, and increased water levels (decreased the amount of habitat available). Decreased nesting habitat for Ring-billed Gulls on other islands increases their density, and subsequent chance of destroying Piping Plover eggs, on Pine Island, Morris Point, and Oak Point. Immediate and continued removal of mammalian predators is the most essential element of a successful management plan for Piping Plovers at LOTW. Restriction of human activity on the islands should continue. The SNA signs seem to be successful and should be maintained.