How Cheap Is Soaring Flight in Raptors? A Preliminary Investigation in Freely-Flying Vultures Duriez, Olivier ; Kato, Akiko ; Tromp, Clara ; Dell'Omo, Giacomo ; Vyssotski, Alexei L. ; Sarrazin, François ; Ropert-Coudert, Yan Abstract Publication: PLoS ONE Pub Date: January 2014 DOI: 10.1371/journal.pone.0084887 Bibcode: 2014PLoSO...984887D