Monitoring Avian Migration with Dedicated Vertical-looking Radar

Abstract

Bird migration is a long-studied phenomena. Geographical challenges faced on route coupled with changing climate and anthropogenic pressures has made migratory species one of the most threatened groups of birds. As migration is an integral part of their life cycle it is important that we understand these movements to make informed conservation decisions. However quantifying migration itself is challenging, made even harder as approximately two thirds of migrants travel at night and at altitudes out of the range of the human eye. Ultimately assistance is needed from appropriate technology to view and record migration. In this thesis, I investigate the effective application of a new innovative vertical-looking radar (VLR) with nutating beam, uniquely dedicated to monitoring migratory birds. Firstly, (chapter 1) I discuss our current understanding of migration and the development of radar systems for detecting animal movements. In chapter 2, I discuss the operation of the VLR and evaluate its capabilities; illustrating with case studies from data collected at the University of Exeter’s Cornwall campus during the autumn of 2015 and spring 2016. Recorded bird echoes are compared and organised into classes to monitor the composition of bird migration. I find the radar to be an effective and non-biased tool for monitoring migration rates, direction and flight heights over varying time frames. Chapter 3 explores the seasonal variation and composition of avian migration as revealed by the radar. Here I find that the classes differ in their flight height, speed and migration rate, though have the same preferred direction of travel within each season. Additionally, there appears to be differences in these characteristics when comparing spring and autumn. Finally, I conclude (chapter 4) my findings and propose areas for refinement and further research. Overall, the aim of this work is to review the suitability of this new radar system for monitoring bird movements and help contribute to our understanding of how wild birds migrate.