in three nesting sites of the patagonian coast of argentina (punta loma, caleta malaspina and puerto deseado) we performed a comparative study of inter- and intraspecific variation of the relationship between dive duration and intervals at surface in three species of patagonian cormorants: the imperial shag (phalacrocorax atriceps), the rock shag (phalacrocorax magellanicus) and the red-legged shag (phalacrocorax gaimardi). the imperial shag presented the highest diving capacity in terms of mean and maximum dive duration. the mean dive duration of the rock shag and the red-legged shag were similar, and were 55% and 74% lower than that of imperial shag, respectively. intervals at surface differed among species and showed a pattern similar to the observed for dive duration. although intervals at surface increased linearly with dive duration in the three species, we observed a marked intraspecific variation when analyzing different colonies for the rock shag. the imperial shag increased intervals at surface in relation to dive duration to a rate between five and eight times higher than the other two species. inter and intraspecific differences in the relationship between these variables were dependent on the studied locality, likely in response to the ecological and environmental characteristics of the marine areas exploited by the birds to feed.