<p>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 (<i>Falco eleonorae</i>) as a simplified study system, we GPS-tracked approximately 7% of an Italian breeding population over two years to evaluate the reliability of tracking data in estimating population-level migratory timing (e.g., the end of pre-nuptial migration). Our findings show that GPS-tracked birds end their pre-nuptial migration later than reported through Citizen Science or in the literature, with simulations revealing that this delay is likely driven by a sample size effect. Extrapolating dates from tracked individuals would result in a delayed population-level estimate by at least 15&#xa0;days, primarily due to insufficient capture of inter-individual variability. We suggest that the required sample size to reliably infer population migration timing increases proportionally with inter-individual variability, often rendering such sample sizes de facto unachievable in most studies. Therefore, we emphasize that tracking studies aiming to infer population-level migratory timings should adopt complementary approaches, integrating additional data sources such as those from direct observations, radar, or ringing. This multifaceted strategy will ensure more robust and accurate estimates for management and conservation purposes.</p>