Despite a wide distribution over much of the New World, the behavior of the Least Grebe (Tachybaptus dominicus) is still poorly known, and most ecological studies have been performed on Northern Hemisphere subspecies. This note reports two observations during breeding in the South American subspecies T. d. brachyrhynchus. Deliberate egg-covering to hide an active nest from an approaching threat was observed, coupled with elusive “hiding” behavior during an opportunistic breeding attempt in a novel habitat (xeric Chaco). Photographic documentation of egg destruction by a domestic Muscovy Duck (Cairina moschata) at a Least Grebe nest is also reported.