title: Estimating updraft velocity components over large spatial scales: contrasting migration strategies of golden eagles and turkey vultures.
abstract: Soaring birds migrate in massive numbers worldwide. These migrations are complex and dynamic phenomena, strongly influenced by meteorological conditions that produce thermal and orographic uplift as the birds traverse the landscape. Herein we report on how methods were developed to estimate the strength of thermal and orographic uplift using publicly available digital weather and topography datasets at continental scale. We apply these methods to contrast flight strategies of two morphologically similar but behaviourally different species: golden eagle, Aquila chrysaetos, and turkey vulture, Cathartes aura, during autumn migration across eastern North America tracked using GPS tags. We show that turkey vultures nearly exclusively used thermal lift, whereas golden eagles primarily use orographic lift during migration. It has not been shown previously that migration tracks are affected by species-specific specialisation to a particular uplift mode. The methods introduced herein to estimate uplift components and test for differences in weather use can be applied to study movement of any soaring species.
authors.affiliation: Department of Civil, Environmental and Geodetic Engineering, The Ohio State University, OH, USA. bohrer.17@osu.edu
authors.forename: Gil
authors.initials: G
authors.lastname: Bohrer
authors.forename: David
authors.initials: D
authors.lastname: Brandes
authors.forename: James T
authors.initials: JT
authors.lastname: Mandel
authors.forename: Keith L
authors.initials: KL
authors.lastname: Bildstein
authors.forename: Tricia A
authors.initials: TA
authors.lastname: Miller
authors.forename: Michael
authors.initials: M
authors.lastname: Lanzone
authors.forename: Todd
authors.initials: T
authors.lastname: Katzner
authors.forename: Charles
authors.initials: C
authors.lastname: Maisonneuve
authors.forename: Junior A
authors.initials: JA
authors.lastname: Tremblay
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001717:Birds / Q000502:physiology*; D020307:Eagles / Q000502:physiology*; D005426:Flight, Animal / Q000502:physiology*; D013045:Species Specificity; D014481:United States; D014887:Weather; D014919:Wind