Decision-making by a soaring bird: Time, energy and risk considerations at different spatio-temporal scales

Roi Harel, Olivier Duriez, Orr Spiegel, Julie Fluhr, Nir Horvitz, Wayne M. Getz, Willem Bouten, François Sarrazin, Ohad Hatzofe, Ran Nathan

Research output: Contribution to journalArticlepeer-review

Abstract

Natural selection theory suggests that mobile animals trade off time, energy and risk costs with food, safety and other pay-offs obtained by movement. We examined how birds make movement decisions by integrating aspects of flight biomechanics, movement ecology and behaviour in a hierarchical framework investigating flight track variation across several spatio-temporal scales. Using extensive global positioning system and accelerometer data from Eurasian griffon vultures (Gyps fulvus) in Israel and France, we examined soaring–gliding decision-making by comparing inbound versus outbound flights (to or from a central roost, respectively), and these (and other) homerange foraging movements (up to 300 km) versus long-range movements (longer than 300 km). We found that long-range movements and inbound flights have similar features compared with their counterparts: individuals reduced journey time by performing more efficient soaring–gliding flight, reduced energy expenditure by flapping less and were more risk-prone by gliding more steeply between thermals. Age, breeding status, wind conditions and flight altitude (but not sex) affected time and energy prioritization during flights. We therefore suggest that individuals facing time, energy and risk trade-offs during movements make similar decisions across a broad range of ecological contexts and spatial scales, presumably owing to similarity in the uncertainty about movement outcomes.

Original languageEnglish
Article number20150397
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Volume371
Issue number1704
DOIs
StatePublished - 26 Sep 2016
Externally publishedYes

Keywords

  • Biotelemetry
  • Convective thermals
  • GPS tracking
  • Movement ecology
  • Risk-aversion flight index
  • Soaring–gliding efficiency

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