Factors Affecting Reproductive Success of Wood Storks (Mycteria americana) in East-Central Georgia

Abstract

-From 1984 through 1989, we examined the reproductive success of Wood Storks (Mycteria americana) at the Birdsville colony in east-central Georgia. Average fledging success ranged among years from 0.33 to 2.16 fledglings per nest. For nests that produced fledglings, prey availability was an important factor affecting reproductive success. Yearly average prey densities at foraging sites were significantly correlated with the average number of fledglings produced from successful nests. Among 243 nests observed, all eggs or chicks were lost from 104 (43%) nests. Five factors were associated with the loss of entire clutches or broods. During the two driest years, 1985 and 1988, raccoon (Procyon lotor) predation eliminated almost all chicks. Many nests were abandoned early in 1989, following periods of cold weather when the parents appeared to be under stress. In 1985, the birds deserted the colony before egg laying when the area experienced freezing weather. Following nest abandonments within the colony, paired adults that presumably had abandoned their nests were involved in nest takeovers that also caused the loss of eggs and chicks. Three storms during the study caused the loss of a few nests. Some losses were due to unknown factors. The importance of these mortality factors varied from year to year. Nest abandonments and subsequent aggression seem to be related to cold periods early in the season. Raccoon predation seems to be related to drying out of the water under the colony. This suggests that the storks have a window in time when it is best to breed-after the winter and early spring cold weather and before the water dries under the colony in the summer. Received 4 December 1991, accepted 15 November