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.1. 岛屿生态系统极易受到外来物种的严重冲击，尤以夜行性捕食者为甚。棕树蛇（Boiga irregularis）在入侵关岛后不久，便几乎彻底清除了当地原生鸟类区系。从邻近岛屿开展的种群再引入可恢复本土鸟类群落，但此类项目需在经过严格管控的区域实施，以便对蛇类种群实施有效防控。然而，现有再引入实践往往缺乏关键生物学数据，比如存在夜行性捕食者时的夜行栖地利用与空间利用模式。为指导相关保护工作，我们在未受棕树蛇入侵的邻近塞班岛，针对食果鸟类群落的日间与夜间栖地及空间利用模式展开了系统研究。 2. 本研究借助无线电遥测技术与贝叶斯框架，首先对比了资源管理者通常可获取的两类核心数据——日间家域（diurnal home range, DHR）与栖地选择，这类数据往往是再引入规划的基础；同时我们还对比了另一类常难以获取但在夜行性捕食威胁较高时至关重要的夜行栖地利用数据。 3. 不同鸟类的日间家域面积存在种内与种间差异，其中密克伦八哥（Aplonis opaca）的日间家域面积至少比其他物种大45公顷。对于所有研究物种而言，夜间栖息位点通常在日间家域范围内呈空间聚集分布，且栖息范围更小。有两个物种在日间家域外栖息的概率更高，但即便超出家域范围，其栖息位点也往往距日间家域边界不足200米。所有物种在日间与夜间均优先选择森林栖地，部分物种更偏好原生林而非非原生林。 4. 综合与应用：若鸟类个体在日间家域内随机栖息，那么针对棕树蛇的全域种群管控或许是部分物种再引入项目的唯一可行方案。但本研究结果显示，所有研究物种均呈现出聚集式栖息与较高的栖地忠实性。若这种栖地忠实性普遍存在，那么即便日间家域延伸至未受保护的周边生境矩阵中，栖息于蛇类种群已被大幅抑制或清除的围栏区域内的个体，仍可获得较高的存活率。日间与夜间的栖地选择存在高度重叠，这表明管控区域应以原生林为主，非原生林仅作为次要补充。在存在夜行性捕食者的生态系统中，明晰日间与夜间栖地利用的变异规律，可为保护决策提供更科学的依据。