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Heart Rate and Sympathetic Activity Fell When a Human Came Within 10 m of Large-billed Crows

Large-billed crow perched on a sign in Tennōji Park, Osaka
Research · Physiology

A 2026 short communication from Japan measured how captive large-billed crows (Corvus macrorhynchos) responded physiologically as a person approached them. The researchers recorded electrocardiograms and analysed both heart rate and variation in the intervals between heartbeats to assess the autonomic nervous system.

The autonomic nervous system regulates involuntary functions such as heart activity. Its sympathetic branch is generally associated with physiological mobilisation during arousal and challenge. Heart-rate variability provides information about how autonomic control changes even when the bird’s outward behaviour alone does not reveal its internal physiological state.

The clearest shift appeared within 10 metres

The striking result was not an increase in cardiac activation as the human came closer. Instead, when the experimenter reached 10 metres or less from the crow, heart rate fell sharply and the heart-rate-variability analysis indicated reduced sympathetic activity.

The study therefore documents a close-range physiological transition during human approach rather than a simple increase in cardiac activation.

The experiment used captive birds under controlled conditions, so its result applies to the physiological response measured in that setting rather than directly showing how the same shift relates to flight decisions in free-ranging urban crows.

Sources and image credit

  1. Suzuki, Y., & Izawa, E.-I. (2026). Autonomic responses of Large-billed Crow Corvus macrorhynchos to approaching humans. Ornithological Science, 25(1), 111–116. https://doi.org/10.2326/osj.25.111Primary short communication released on J-STAGE 7 February 2026. Electrocardiograms of captive large-billed crows were recorded while an experimenter approached. Heart rate and sympathetic nervous activity fell sharply when the human reached a distance of 10 m or less.

Image: Laitche / Wikimedia Commons — large-billed crow (Corvus macrorhynchos) in Tennōji Park, Osaka, Japan, photographed 13 December 2023; representative urban species image, not a bird from the physiology experiment · CC BY-SA 4.0 · Source

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