title: Interspecific comparison of the performance of soaring migrants in relation to morphology, meteorological conditions and migration strategies.
abstract: BACKGROUND
  Performance of migrating birds can be affected by a number of intrinsic and extrinsic factors like morphology, meteorological conditions and migration strategies. We compared travel speeds of four raptor species during their crossing of the Sahara desert. Focusing the analyses on this region allows us to compare different species under equivalent conditions in order to disentangle which factors affect migratory performance.
  
  
  RESULTS
  We tracked raptors using GPS satellite transmitters from Sweden, Spain and Italy, and evaluated their migratory performance at both an hourly and a daily scale. Hourly data (flight speed and altitude for intervals of two hours) were analyzed in relation to time of day, species and season, and daily data (distance between roosting sites) in relation to species, season, day length and tailwind support.
  
  
  CONCLUSIONS
  Despite a clear variation in morphology, interspecific differences were generally very small, and did only arise in spring, with long-distance migrants (>5000 km: osprey and Western marsh-harrier) being faster than species that migrate shorter distances (Egyptian vulture and short-toed eagle). Our results suggest that the most important factor explaining hourly variation in flight speed is time of day, while at a daily scale, tailwind support is the most important factor explaining variation in daily distance, raising new questions about the consequences of possible future changes in worldwide wind patterns.
authors: Estación Biológica Terra Natura, Vertebrates Zoology Research Group, CIBIO, University of Alicante, Alicante, Spain. ugomellone@libero.it
authors: Ugo
authors: U
authors: Mellone
authors: Raymond H G
authors: RH
authors: Klaassen
authors: Clara
authors: C
authors: García-Ripollés
authors: Ruben
authors: R
authors: Limiñana
authors: Pascual
authors: P
authors: López-López
authors: Diego
authors: D
authors: Pavón
authors: Roine
authors: R
authors: Strandberg
authors: Vicente
authors: V
authors: Urios
authors: Michalis
authors: M
authors: Vardakis
authors: Thomas
authors: T
authors: Alerstam
mesh_terms: D000352:Africa, Northern; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D020304:Raptors / Q000502:physiology*; D012621:Seasons