| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 1985. Psychology Bibliography: leaves 81-86. A small insular population of nesting Spotted Sandpipers (Actitis macularia), estimated at 38-45 individuals, was studied during the summers of 1979 and 1980. Daily observations were wade from late May when birds first arrived through mid-July when most eggs had hatched. Some individuals were colour banded or otherwise marked. During the two seasons 31 nests were located and histories resulting from daily observations at these nests are summarized. Contrary to reports of some researchers (e.g. Oring & Knudson 1972), perceived size differences and plumage markings in this population did not allow reliable determination of sex in the field. Extensive observations were made at nests where one or both individuals were marked to determine whether one or both pair members participated in clutch and brood tending activities. Marked individuals were also followed when off the nest to assess use of feeding areas. Of 14 marked females, two were known to mate with multiple males and some details of these relationships are presented. Aggression was rare and seemed to occur primarily in situations where existing pair relationships were challenged or in instances of "mate defense." Territorial behaviour by males and females was not apparent and overlapping feeding areas were observed. Theoretical arguments which suggest selective pressures for incubation and brood tending by one member of a breeding pair are reviewed and their relevance to the Spotted Sandpiper mating system are discussed.
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