Groping in the Fog: Soaring Migrants Exhibit Wider Scatter in Flight Directions and Respond Differently to Wind Under Low Visibility Conditions

Paolo Becciu, Michele Panuccio, Giacomo Dell’Omo, Nir Sapir

Research output: Contribution to journalArticlepeer-review

Abstract

Atmospheric conditions are known to affect flight propensity, behaviour during flight, and migration route in birds. Yet, the effects of fog have only rarely been studied although they could disrupt orientation and hamper flight. Fog could limit the visibility of migrating birds such that they might not be able to detect landmarks that guide them during their journey. Soaring migrants modulate their flight speed and direction in relation to the wind vector to optimise the cost of transport. Consequently, landmark-based orientation, as well as adjustments of flight speed and direction in relation to wind conditions, could be jeopardised when flying in fog. Using a radar system operated in a migration bottleneck (Strait of Messina, Italy), we studied the behaviour of soaring birds under variable wind and fog conditions over two consecutive springs (2016 and 2017), discovering that migrating birds exhibited a wider scatter of flight directions and responded differently to wind under fog conditions. Birds flying through fog deviated more from the mean migration direction and increased their speed with increasing crosswinds. In addition, airspeed and groundspeed increased in the direction of the crosswind, causing the individuals to drift laterally. Our findings represent the first quantitative empirical evidence of flight behaviour changes when birds migrate through fog and explain why low visibility conditions could risk their migration journey.

Original languageEnglish
Article number745002
JournalFrontiers in Ecology and Evolution
Volume9
DOIs
StatePublished - 29 Oct 2021

Bibliographical note

Funding Information:
Data collection was supported by Terna Rete Italia S.p.A. We thank Ornis italica which supported our fieldwork. We thank all the people involved in the field as radar operators and as birdwatchers. MP was partially funded by COST-European Cooperation in Science and Technology through the Action ES1305 European Network for the Radar Surveillance of Animal Movement (ENRAM). We would also like to thank G. Bohrer and E. Kirsch for their useful comments that substantially improved our work, and S. Turjeman for the English revisions.

Funding Information:
This work was partially funded by Terna Rete Italia S.p.A., COST-European Cooperation in Science and Technology through the Action ES1305 European Network for the Radar Surveillance of Animal Movement (ENRAM), and University of Haifa, Haifa, Israel.

Funding Information:
Data collection was supported by Terna Rete Italia S.p.A. We thank Ornis italica which supported our fieldwork. We thank all the people involved in the field as radar operators and as birdwatchers. MP was partially funded by COST-European Cooperation in Science and Technology through the Action

Publisher Copyright:
Copyright © 2021 Becciu, Panuccio, Dell’Omo and Sapir.

Keywords

  • Honey Buzzard
  • Strait of Messina
  • bird migration
  • flight behaviour
  • movement ecology
  • radar aeroecology
  • visual navigation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology

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