FACTORS AFFECTING RENESTING IN AMERICAN COOTS

I studied renesting behavior of American Coots (Fulica americana) in south-western Manitoba during 1987-1991. Coots were persistent renesters, replacing 68% of 281 destroyed clutches. Renesting rates varied annually and seasonally, but were unaffected by previous investments in egg formation or incubation. Renest intervals averaged 2.1 +/- 1.8 days (1 SD; n = 127) following clutch loss during laying and 6.4 +/- 1.1 days (n = 28) following clutch loss during incubation. Renest intervals did not vary, or varied only slightly (r2 less-than-or-equal-to 0.11), with respect to year, date, supplemental feeding, number of previous nesting attempts, previous clutch size, previous egg size, and stage of incubation. Clutch size of renests was usually one to two eggs smaller than clutch size of initial nests, but this was entirely an artifact of later nest initiation dates for renests. Clutch and egg sizes of renesting coots were unaffected by levels of previous investment in egg formation or incubation. After controlling for seasonal effects, approximately 30% of the variation in renest clutch size and 65% of the variation in renest egg size were attributable to individual females (i.e., within-season repeatability). These observations suggest that renesting coots are constrained by time or habitat quality, but not by the amount of food or nutrient reserves available for egg production.