| Summary: | Philopatry, site tenacity, and mate fidelity were examined in a 5-yr study of a population of male-territorial, monogamous Semipalmated Sandpipers (Calidris pusilla) breeding at La Perouse Bay, near Churchill, Manitoba. There was no sex bias in natal philopatry and no significant difference in adult philopatry, although males tended to return to the breeding area at higher frequencies than females. However, males nested significantly closer to previous nests than did females. Pairs that had reunited did not move as far from their previous nest site as birds that had changed mates, and this effect was more pronounced in females. Birds that had nested successfully the previous year returned at higher rates than those that had been unsuccessful. However, there was no significant difference in distance moved from a previously successful vs. unsuccessful nest. There also was no significant difference in site tenacity when distances one and two years or two and three years apart were compared. However, nest distances increased significantly when three years had elapsed between utilization of sites. Each year approximately 50% of the marked birds in the study area had reunited with their mate of the previous year. If both members of the pair returned, close to 80% remained paired. There was no tendency for birds that had "divorced" to have been less successful nesters in the previous year, compared to pairs that had reunited. Subsequent nesting success was not significantly different between birds that had changed or retained mates. However, in 1 of 4 yr, nests of pairs that had changed mates hatched significantly later than did those of remated pairs. Received 23 April 1984, accepted 4 October 1984.
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