The births of brown brocket deer ( Mazama gouazoubira) in a secondary lower montane forest called "yunga" in northwestern Argentina were compared with rainfall. Analyses were performed with rainfall and flower-fruit fall in an attempt to determine the possible importance of these seasonal variables in birthing. The births were not directly correlated with rainfall, but rather with the flower and fruit fall of exotic plant species. This may be related to favor the development of fawns, which eat the new and more digestible plant parts, accessible one month after their births.The non-seasonal births observed around the year could be related to the selection by the deer of some plant species that have been introduced into the region (Prunus, Morus and Psidium), have a longer fruiting span than the scarce native plant species.