Data from: Spatial dynamics of habitat use informs reintroduction efforts in the presence of an invasive predator

1. Islands experience major impacts from introduced species, especially nocturnal predators. The Brown Treesnake (Boiga irregularis) extirpated almost the entire native avifauna on Guam shortly after introduction. Reintroductions from neighboring islands can restore bird communities but will take place in heavily managed units where snake populations can be controlled. Yet reintroductions often proceed without relevant biological information such as nocturnal habitat and space use when nocturnal predators are present. To guide efforts, we studied diurnal and nocturnal habitat and space use by the avian frugivore community on the nearby island of Saipan where the snake is absent. 2. Using radio telemetry and a Bayesian framework, we first compared data typically accessible to resource managers (diurnal home range [DHR] and habitat selection) and which often forms the basis of reintroduction plans. We contrast this with data on nocturnal habitat use that is often not available but relevant when nocturnal predation threat is high. 3. DHR size varied within and among species with Micronesian Starlings (Aplonis opaca) having DHRs at least 45 ha larger than other species. For all species, night roost locations were generally spatially clustered within a DHR and covered a smaller spatial extent. Two species had higher probabilities of roosting outside DHR boundaries but, when outside, roosts were often within 200 m of the DHR boundary. All species selected forested habitats during day and night, with some species choosing native forest over non-native habitat. 4. Synthesis and applications If individuals roosted randomly throughout DHR’s, landscape-level suppression of B. irregularis might be the only viable option for reintroductions of some species. However, individuals of all species showed clustered roosting and high site fidelity. If site fidelity is common, then individuals that roost within fenced areas where snake populations are severely reduced or eliminated will experience high survivorship even if DHRs extend into surrounding unprotected matrix. There was large overlap in habitat selection during day and night indicating managed areas should be composed of native forest with non-native forests of secondary importance. In systems with nocturnal predators, understanding variability in diurnal and nocturnal habitat use could lead to better informed decisions