Quantifying phenology and migratory behaviours of hummingbirds using single-site dynamics and mark-detection analyses

Nuanced understanding of overwintering movements of partially migratory birds is paramount to species and habitat conservation. Using nascent statistical methods, we identified migratory strategies of birds outfitted with radio-frequency identification (RFID) tags detected at RFID feeders in two sites in California, USA. We quantified proportions of migrants and residents and the seasonal movement phenology of two species: Allen's and Anna's hummingbirds. We found species-specific differences in proportions of migrants and residents. Both Allen's and Anna's hummingbirds exhibited characteristics of facultative migratory behaviour. We also quantified apparent annual survival for each migratory strategy and found that residents had significantly higher probabilities of survival. Low survival estimates for migrants suggest that a high proportion of birds in the migrant group permanently emigrated from our study sites. Considered together, our analyses suggest that hummingbirds in both northern and southern California sites partake in diverse and highly plastic migratory behaviours. Our assessment elucidates the dynamics underlying idiosyncratic migratory behaviours of two species of hummingbirds, in addition to describing a framework for similar assessments of migratory behaviours using the multi-state open robust design with state uncertainty (MSORD-SU) model and single-site dynamics.These data were analysed using Program MARK via RMark version 2.2.7.The dataset "EnglishEtAl2022_CaptureHistories.csv" includes individual monthly detection histories for each tagged bird in the study. Each detection history comprises 36 characters corresponding to each month from March 2018 to February 2021. Detections were encoded with one of three characters: `0` denotes no detection within the monthly period, `u` denotes that the bird was detected, but detection took place outside of the 4 winter months (November to February) and its state is therefore unknown, and lastly `R` denotes that a bird was detected during winter and is therefore classified as a resident