Biodiversity benefits of an ecosystem engineer are negated by an invasive predator

Ecosystem engineers play a vital role in community assembly by modifying the environment to create novel habitat features. Woodrats (Neotoma sp.) build and maintain intricate stick-nests that stockpile organic materials and create habitat for other small species. The Key Largo woodrat (Neotoma floridana smalli) is an endangered subspecies endemic to Key Largo, Florida, USA, that has undergone substantial declines due to habitat loss and predation by invasive predators. We leveraged data from a camera trap monitoring grid at supplemental woodrat nest structures to survey bird communities to evaluate the role of woodrat nest use and stick-nest building related to bird abundance using generalized linear models. We predicted that woodrat occurrence and stick-nest building would positively correlate with bird species richness and abundance due to the creation of habitat structures that support prey for birds. To test this, we analyzed the relationship that bird abundance and species richness have with several indicators of woodrat activity along with other environmental and predator variables. Bird abun-dance was positively associated with woodrat supplemental nest use and stick-nest building. However, these positive associations were largely negated by the presence of free-roaming cats (Felis catus), an invasive predator, and dampened by proximity to human development. We provide evidence that woodrats may have cascading effects on their local food webs by creating foraging grounds for birds, but this positive relationship is disrupted by the presence of an introduced predator.