Repository containing all data, source code and manuscript for the study:
Nussbaumer, R., L. Kirao, F. Liechti, and C. Jackson. 2022. Using ringing data to inform geolocator deployment: a case study of the Red-capped Robin-chat Cossypha natalensis in East Africa. Journal of Field Ornithology 93(2):8. 10.5751/JFO-00113-930208
Thanks to their light weight and low cost relative to GPS trackers, light-level geolocators are uniquely positioned to uncover bird migration patterns across less well-financed and understudied regions of the world. A main drawback of geolocators is the need to recapture equipped birds to retrieve the data. Maximizing the recapture rate is therefore critical to the success of any geolocator study, while contributing to minimizing bird disturbance. In this paper, we present a methodology drawing on historical ringing data in order to optimize the deployment of geolocators, both in terms of how many birds can be equipped, and when/which birds to equip in order to maximize recapture. We illustrate this methodology with a geolocator study of Red-capped Robin-chats on the coast of Kenya and find that it accurately estimates how many geolocators to order. It also provides insights into which classes of birds (based on age, capture history, and timing within the season) are most likely to be recaptured, which sheds light on potential recapture biases to be accounted for in the research questions. Finally, the analysis of recapture rates also provides a baseline to assess the impact of geolocators.
