Telemetry Alone May Not Be Reliable for a Correct Determination of Population-Level Migration Timing: Lessons from Eleonora’s Falcon (falco Eleonorae)

Tracking technologies have revolutionized the study of bird migration, offering unparalleled insights into ecology, behaviours and flyways. However, due to the typically small proportion of individuals tracked, their reliability for estimating population-level migratory parameters, particularly temporal aspects, remains poorly understood. Although this uncertainty is acceptable in behavioural or ecological studies, scaling up from individuals to populations to infer migratory timing (i.e., onset or end) has critical implications for management and conservation. For example, in the European Union, accurately identifying migration onset is essential for setting harvesting calendars for huntable species. Using Eleonora’s Falcon (Falco eleonorae) as a simplified study system, we GPS-tracked approximately 7