Because obligate corallivorous butterflyfish feed exclusively on coral polyps, they are particularly sensitive to changes in coral cover and its spatial distribution. To understand how such differences in coral cover influence obligate corallivores, we examined the densities and foraging behavior of Melon butterflyfish Chaetodon trifasciatus across three reefs in the Lakshadweep archipelago. These reefs suffered differential bleaching mortality after the 2010 El Niño Southern Oscillation, resulting in wide variation in coral cover and community composition. Despite these differences, C. trifasciatus were able to persist at similar densities across reefs. However, our analysis of high-resolution video recordings of multiple focal fish revealed that time budgets, bite rates, and diet selectivity differed significantly. Fish in resource-poor reefs spent more time moving between coral patches and less time foraging than ones in relatively resource-rich reefs. We also found that fish in resource-poor reefs had higher bite rates and were less selective in their foraging. Our results provide novel insights into how obligate corallivores cope with even large differences in resource availability. At a time when we are rapidly losing corals to repeated climate-induced bleaching events, this flexibility may represent a critical mechanism that enables persistence of obligate corallivores in resource-poor reefs, even if it does not guarantee longer-term survival.