If a bird flies in the forest, does an insect hear it?

Area of Science:

• Ecology
• Bioacoustics
• Animal Behavior

Background:

• Birds are significant predators of various eared insects like moths, butterflies, crickets, and cicadas.
• Insects possess auditory systems that may have evolved to detect predators.

Purpose of the Study:

• To investigate if insect ears can function as 'bird detectors'.
• To determine if foraging birds produce detectable flight sounds.
• To assess insect auditory perception of bird flight sounds.

Main Methods:

• Recorded flight sounds of Eastern phoebes and chickadees during foraging.
• Measured insect hearing thresholds and sound levels of bird flight.
• Recorded auditory nerve cell responses in moths and butterflies to bird flight sound playback.

Main Results:

• Foraging birds produce broadband flight sounds (18-20 Hz) linked to wing beats.
• Insects can detect bird flight sounds from at least 2.5 meters.
• Auditory nerve cells of moths and butterflies responded to bird flight sounds, indicating detectability across hearing frequencies.

Conclusions:

• Foraging birds generate detectable flight sound cues for eared insects.
• Insect ears may serve as 'bird detectors', providing an early warning system.
• Further research is needed to explore insect exploitation of these cues and potential avian acoustic camouflage.