Wikipedia's significant gender bias is widely acknowledged. In this paper we analyze the Spanish Wikipedia with the aim of estimating the percentage of women editors and measuring their engagement and editing practices with respect to their men counterparts. To identify the gender of Wikipedia registered users, we analyzed both the information contained in their user profile and the information provided by users about themselves on their personal user pages. Using our own coding procedure, it is possible to identify a greater number of women than by relying only on the gender reported in their user profile. Combining both methods, our results show that the percentage of women is small, a meagre 11.6% of all analyzed editors, though there is still a significant percentage of users whose gender cannot be determined by either method. Men outnumber women in all Wikipedia namespaces in a ratio that is always equal to or greater than 3:1. This fact can be partially explained by the lesser persistence of women editors, who tend to leave Wikipedia much more quickly. There is, however, a small group of veteran women editors who, in some cases, surpass men editors in terms of their editing practices and participation in different Wikipedia namespaces.