Research comparing dive durations and inter-dive intervals of stiff-tailed diving ducks, which is important for understanding differences in species ecology, is lacking for the non-migratory Masked Duck (Nomonyx dominicus) and West Indian Ruddy Duck (Oxyura jamaicensis jamaicensis), and the migratory Northern Ruddy Duck (Oxyura jamaicensis jamaicensis). Although the Northern Ruddy Duck and West Indian Ruddy Duck are considered the same species, we treated them separately to evaluate possible ecological differences. All three were observed at the same time in the same place in Laguna Cartagena National Wildlife Refuge, Puerto Rico. Dive durations and inter-dive intervals were recorded for Masked Duck (n = 60), Northern Ruddy Duck (n = 70), and West Indian Ruddy Duck (n = 445) from 1 January through 30 April 2015 and 2016. The Northern Ruddy Duck had a longer mean (± SE) dive duration (22.9 ± 0.75 sec) than the West Indian Ruddy Duck (18.8 ± 0.02 sec). Northern Ruddy Ducks likely had longer dive times because of their larger body size and migratory behavior.