CLUTCH SIZE AND FLEDGING SUCCESS IN THE TURQUOISE-BROWED MOTMOT

ABST•,ACT.--Clutches of 4 eggs accounted for 64-73% of all clutches laid in 3 yr by a population of Turquoise-browed Motmots (Eumomota superciliosa) in Yucatan, Mexico. The consistently high frequency of 4-egg clutches was associated with only a slight advantage in fledging success relative to clutches of 3 eggs, which ranged in frequency from 11% to 33%. Differences in number of young fledged and proportion of hatchlings fledged were not statistically significant over 3 yr or in any particular year. Clutches of 4 yielded more surviving young in 2 of 3 yr, averaging 2.02 compared to 1.71 for clutches of 3. The proportion of hatchlings that fledged was higher in broods of 3 (overall = 0.67) than in broods of 4 (overall = 0.55) in 2 of 3 yr. The proportion of hatchlings fledged from clutches of 5 (0.36) was lower over 3 yr than that fledged from clutches of 4 or 3. Approximately 40% of nestling mortality in nests that escaped predation was due to starvation. Other known causes included falls from nests and parasitism by maggots. Received 12 July 1984, accepted 9 April 1985.