Expanding North: Tracking the Range Shift of Buff-Bellied Hummingbird ( Amazilia yucatanensis ) Using Citizen Science Data

Background and Research Aims: Recent decades have seen increased sightings of the Buff-bellied Hummingbird ( Amazilia yucatanensis ) northeastward from its historical range, including winter sightings in the southeastern United States, but it remains unclear whether these reflect true range expansion or recent migratory behavior. Therefore, we aimed to determine potential range expansion of A. yucatanensis , and evaluate evidence for seasonal migratory movements. Methods: We analyzed occurrence data from public records in scientific collections and citizen-science platforms. Occurrence records from 1961 to 2020 were filtered and mapped to analyze range expansion and migratory patterns. Distances between northernmost points per decade were measured, and temporal trends were assessed using regression models, and latitudinal, longitudinal, and seasonal shifts were evaluated using Anderson-Darling test. Results: Our results show a steep increase in the number of records of A. yucatanensis after the year 2000, with more than 67,000 occurrence records in the last decade (2011–2020). Spatial analyses revealed a clear and significant expansion of the species’ distribution, with approximately 10 degrees of latitudinal and longitudinal movement. The seasonal occurrence records and the full distribution range show the same pattern, showing more data after 2001–2010. Seasonal analyses also showed occurrences in all months of the year, with similar numbers of records between spring–summer and fall–winter, except for a marked increase in fall–winter observations during the last decade. Conclusion: Overall, the evidence indicates that A. yucatanensis have expanded their distribution range over time, with no indication of a migratory pattern. Implications for Conservation : Citizen science data revealed a northward range expansion, providing useful insights for conservation. Targeted monitoring and multidisciplinary research are needed to clarify demographic trends, habitat requirements, and the factors driving range shifts, in order to inform effective conservation strategies.