Old habits die hard: pigeons maintain route fidelity but reduce flight altitude when exposed to a raptor-like robot

Abstract

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  Experienced homing pigeons faced repeated RobotFalcon attacks along familiar routes.
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  Birds lowered altitude starting ∼200 m before reaching the simulated predator.
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  Pigeons did not abandon familiar flight routes after repeated predator encounters.
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  No clear anticipatory response to the predator was detected.

Prey organisms use a range of adaptive strategies to mitigate predation risk, including camouflage, predator deterrence by collective antipredator behaviours, specialized predator evasion tactics and spatial or temporal avoidance of predators. The latter may involve memorizing locations of nonlethal predator encounters and altering movement routines to subsequently avoid areas where such encounters are more likely, in line with the ‘landscape of fear’ concept. We investigated whether and how experienced homing pigeons, Columba livia, altered their homing behaviour upon repeated exposures to simulated attacks by a robot (‘RobotFalcon’) mimicking a peregrine falcon, Falco peregrinus, a common aerial predator of pigeons, along their consolidated homing route. Pigeons showed evidence of immediate responses to predator detection, considerably reducing their flight altitude when they approached the RobotFalcon, starting at ∼200 m from it, and maintained a lower altitude when leaving the RobotFalcon area. Yet, pigeons showed no evidence of altering their path to avoid the area where they were more likely to encounter the RobotFalcon, even in subsequent flights when the RobotFalcon was absent, indicating that the tendency to retrace consolidated routes was not affected by predation risk. Our results indicate that pigeons can adaptively respond to immediate predation risk by flying closer to the ground, which may reduce the success of aerial predator attacks. These findings suggest that maximizing energy efficiency and flying over well-known landscapes, which may make immediate predator responses more effective, are prioritized over minimizing predation risk by flying across novel and unknown environments.

Prey organisms use a range of adaptive strategies to mitigate predation risk, including camouflage, predator deterrence by collective antipredator behaviours, specialized predator evasion tactics and spatial or temporal avoidance of predators. The latter may involve memorizing locations of nonlethal predator encounters and altering movement routines to subsequently avoid areas where such encounters are more likely, in line with the ‘landscape of fear’ concept. We investigated whether and how experienced homing pigeons, Columba livia, altered their homing behaviour upon repeated exposures to simulated attacks by a robot (‘RobotFalcon’) mimicking a peregrine falcon, Falco peregrinus, a common aerial predator of pigeons, along their consolidated homing route. Pigeons showed evidence of immediate responses to predator detection, considerably reducing their flight altitude when they approached the RobotFalcon, starting at ∼200 m from it, and maintained a lower altitude when leaving the RobotFalcon area. Yet, pigeons showed no evidence of altering their path to avoid the area where they were more likely to encounter the RobotFalcon, even in subsequent flights when the RobotFalcon was absent, indicating that the tendency to retrace consolidated routes was not affected by predation risk. Our results indicate that pigeons can adaptively respond to immediate predation risk by flying closer to the ground, which may reduce the success of aerial predator attacks. These findings suggest that maximizing energy efficiency and flying over well-known landscapes, which may make immediate predator responses more effective, are prioritized over minimizing predation risk by flying across novel and unknown environments.