The fact that the rainy season to dry season in the seasonal tropics is a continuum calls for subjective judgment regarding division of the year into wet/dry seasons. On BCI, in the center of the isthmus, where total annual precipitation is ca. 2700 mm, rainfall is lowest in January, February, and March, begins to increase in April, plateaus in May–October, reaches the maximum in November, decreases from November to December (to about the level of the May–October plateau), declines sharply from December to January, and finally reaches the minimum in March (Croat, 1978). Based on these data, we recognized three seasons in this study: dry season, January–March; early rainy season, April–July; and late rainy season, August–December.