Species on oceanic islands are more likely to be endemic as well as more extinction-prone than those on continents. The Galápagos Rail Laterallus spilonotus, endemic to the Galápagos Archipelago, is presently known to occur on just four of its seven previously occupied islands and is facing multiple threats to its persistence. In this study, we compared the rail’s occurrence and abundance at 193 survey points between 2000 and 2007 on Santa Cruz Island and examined the influence of an invasion of the habitat of the species by the exotic Red-barked Quinine Tree Cinchona pubescens. We detected a 13% reduction in rail occurrence and a 31% reduction in abundance between 2000 and 2007. Rail abundance declined more in low elevation areas (< 719 m) and outside of Cinchona pubescens removal areas but not in areas where Cinchona pubescens was removed. Insofar as Galápagos Rails responded positively to management actions that promote and maintain native vegetation, we conclude that restoration projects that restore native vegetation communities benefit this apparently declining endemic bird for which more focused conservation attention is warranted.