Annual fecundity of a neotropical bird during years of high and low rainfall

We investigated how variation in the timing and amount of annual precipitation influenced annual variation in the fecundity of the Spotted Antbird (Hylophylax naevioides) in central Panama from 1998 to 2001. The onset of nesting varied significantly by year and corresponded with a notably strong episode of El Niño-Southern Oscillation that generated variation by year in dry-season precipitation and the onset of wet-season rains. The end of nesting, however, was not influenced by annual variation in rainfall. Fecundity was also similar each year despite pronounced variation in wet-season precipitation. Although breeding pairs attempted an average of almost five nests per year, slightly less than one nest attempt per pair was successful. Annual fecundity was 1.5 fledglings per pair, exceeding the turnover of territorial adults in this population. Extended parental investment in care of fledglings delayed renesting and consequently limited subsequent opportunities to breed within the season. Predation and duration of parental care likely influence annual fecundity more than variation in environmental conditions.