Four pairs of the poorly understood tropical mockingbird Mimus gilvus were captured and color banded at a grassland in Maracaibo, Venezuela in June 1997. Throughout the following 8 months, individuals were observed two days per week for 4 hours each. We recorded courtship behaviour, nest construction, incubation, parental care, territory defense and timing of reproductive cycle. Pairs lived in defined territories defended primarily by the male. Both sexes participated in nest building which began at the start of two rainy seasons: April and October. Between April and June, 80 % of nests were parasited by the shiny cowbird (Molothrus bonariensis). No parasitism was recorded in the later nesting season. Consequently, breeding success for the April and October seasons was 20 % and 83 % respectively. Only the female incubated and the mean clutch size was 2.2 eggs.
Keywords: mimus gilvus, molothrus bonariensis, breeding success, courtship, clutch size, parental care, parasitism