Archival geolocators have transformed the study of small, migratory organisms but analysis of data from these devices requires bias correction because tags are only recovered from individuals that survive and are re-captured at their tagging location. We show that integrating geolocator recovery data and mark–resight data enables unbiased estimates of both migratory connectivity between breeding and nonbreeding populations and region-specific survival probabilities for wintering locations. Using simulations, we first demonstrate that an integrated Bayesian model returns unbiased estimates of transition probabilities between seasonal ranges. We also used simulations to determine how different sampling designs influence the estimability of transition probabilities. We then parameterized the model with tracking data and mark–resight data from declining Painted Bunting (Passerina ciris) populations breeding in the eastern United States, hypothesized to be threatened by the illegal pet trade in parts of their Caribbean, nonbreeding range. Consistent with this hypothesis, we found that male buntings wintering in Cuba were 20% less likely to return to the breeding grounds than birds wintering elsewhere in their range. Improving inferences from archival tags through proper data collection and further development of integrated models will advance our understanding of the full annual cycle ecology of migratory species.
LAY SUMMARY
Recent advances in the miniaturization of tracking devices have transformed the ability of researchers to track small migratory birds throughout their journeys. However, the small size of these devices prevents transmitting the data to satellites, so birds must be recaptured to obtain the tracking data.
Because tracking data can only be obtained from individuals that survive and return the following year, these data underestimate how many birds migrate to regions where they are less likely to survive, which may lead to incorrect conclusions about what areas are most important to a species.
We show that more accurate estimates of migratory patterns can be obtained by combining the data from the tracking tags with information about the survival of individuals within each population.
Application of this method to tracking data from Painted Buntings revealed that males wintering in Cuba experience nearly 15–20% lower survival than males wintering elsewhere in the range.
