Clutch and egg size variation in the coot Fulica atra breeding on fishponds in eastern Poland – test of the optimal egg dimensions hypothesis

POLAK M. 2010. Clutch and egg size variation in the coot Fulica atra breeding on fishponds in eastern Poland – test of the optimal egg dimensions hypothesis. Acta zoologica cracoviensia, 53A(1-2): 35-40. Abstract. Clutch and egg size variation of the coot, Fulica atra, was studied in eastern Poland from 2005 to 2008. The study areas were extensively managed fish farms in the Lublin region. A total 797 eggs from 106 clutches were measured during four nesting seasons. Mean clutch size was 7.52 ± 1.59 (range 5-14), modal clutch size was 7. Average values of the egg dimensions are as follows: egg length – 52.70 ± 2.33 mm, egg breadth – 36.52 ± 1.22 mm and egg volume 35.72 ± 3.44 cm3. Egg dimensions were positively correlated. No significant differences in clutch and egg sizes during the four seasons were found. This suggests that the environmental conditions in the studied fishponds during the study period did not change or had no influence on egg size. There was no significant relationship between egg dimensions and clutch size and the study does not support predictions based on the hypothesis of optimal clutch/egg size.