Migration Routes and Strategies in a Highly Aerial Migrant, the Common Swift Apus apus, Revealed by Light-Level Geolocators Åkesson, Susanne ; Klaassen, Raymond ; Holmgren, Jan ; Fox, James W. ; Hedenström, Anders Abstract Publication: PLoS ONE Pub Date: July 2012 DOI: 10.1371/journal.pone.0041195 Bibcode: 2012PLoSO...741195A