We studied the gonadal and molt cycle of three species of Columbina ground-doves in seasonal savannas of Venezuela to explore whether gonadal development is related to seasonal patterns of rainfall. The study site is a strongly seasonal, open woodland-savanna displaying a predictable alternation of dry and wet seasons, providing strong cues on environmental periodicity and on the variation in the level of food resources associated with those fluctuations. All three species of doves had an extensive breeding season, bred (although not exclusively) during the dry season, had fully functional testes independent of rainfall, and displayed a relatively small seasonal fluctuation in testes size. Nevertheless, even though all three species were exposed to similar ambient conditions and their diets overlapped extensively, there were noticeable differences in their testicular cycles, and no simple generalizations regarding the possible stimulatory roles of photoperiod or rainfall were apparent. The testes of most Scaled Doves (C. squammata) remained fully or partly recrudesced throughout the year, but a significant reduction in testes size occurred in May, at the beginning of the rainy season, when the size of the soil seed bank should be smallest. Maximum testes sizes were reached from November through March during the beginning and peak of the dry season, when the seed bank is expected to be large. In this species, neither rainfall nor longer photoperiod had a stimulatory effect on testicular development. Ruddy Ground-Doves (C. talpacoti) had an extensive, and seemingly double, breeding season encompassing the latter part of the dry season and the rainy season. Male C. talpacoti had fully functional testes in the peak of the dry season, some three months ahead of the first rains. Hence, as in the Scaled Dove, the influence of rainfall on testicular development was not apparent, but testicular recrudescence coincided with the period of increasing day length and we cannot rule out a possible degree of photoresponsiveness in Ruddy Ground-Doves. Males of Plain-breasted Ground-Doves (C. minuta) underwent testicular regression in April and May, at the beginning of the rainy period, and testicular recrudescence progressed along with the advancement of the rainy season. In this species, rainfall, but not increasing photoperiod, could have a stimulatory effect on gonadal development, since testes became smaller as day length increased towards May, but testis size increased until November while days were becoming shorter. In none of the species was the molt of primary wing feathers synchronous, but in all of them there was a tendency not to molt primaries during the peak of the rainy season. At the level of the population, the periods of breeding and wing molt overlapped. The molt was spread over most of the year in all species. An unforeseen finding was a highly biased sex ratio in favor of males among adults in all species.
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Vol. 75 • No. 1