Rainfall amount influences space use and survivorship of Cardellina canadensis (Canada Warbler) on the nonbreeding grounds: An assessment using VHF tracking

Abstract Cardellina canadensis (Canada Warbler) display flexible space use during the nonbreeding season that is only weakly associated with habitat characteristics, while higher local precipitation is linked to increased survival. Understanding the relationships between fitness, space use, climate, and land-use is key to assessing population vulnerability under future precipitation and land-use scenarios. We examined these relationships by estimating home ranges of 29 C. canadensis using manual radio-telemetry in forests across 3 biogeographic regions of the Colombian Andes: the western slope of the Cauca Valley, the eastern slope of the Magdalena Valley and the eastern slope of the Eastern Andes. We assessed the effect of precipitation, habitat quality, and habitat availability on home-range sizes, and estimated weekly and nonbreeding survival. Home-range sizes were weakly associated with habitat variables. Individuals in areas with higher vegetation greenness (normalized difference vegetation index [NDVI]) tended to have smaller home ranges, although support for this pattern was limited and dependent on site-level effects. Variation in home range among sites suggests that broader regional or site-level factors influence space use during the nonbreeding season. Survival was consistently high, averaging 98% monthly and 92% from January through April. Notably, individuals experienced higher survival when precipitation prior to initial capture was higher. Together, our findings indicate that nonbreeding C. canadensis exhibit flexible space use, and that home-range size is only weakly linked to the habitat variables we measured. Furthermore, increased local precipitation enhances survivorship during the nonbreeding season, underscoring the importance of climatic factors during this period. Overall, our findings provide valuable insights into the adaptive behaviors of migratory birds during the nonbreeding season and highlight the critical role of environmental factors in their survival. This knowledge provide insight for conservation strategies to protect the species under changing precipitation and land-use conditions.