Timing breaths between strikes helps woodpeckers generate maximum pecking power. (Credit: LABETAA Andre on Shutterstock)
In A Nutshell
- Woodpeckers exhale forcefully with every peck, using the same “grunting” technique tennis players use to boost their serve power
- They take miniature breaths lasting just 40 milliseconds between rapid-fire strikes, breathing nine times per second during fast tapping
- Eight muscle groups from head to tail work together to turn the bird into a biological hammer, with the neck acting as a stiff handle
- Hip muscles control how hard they peck, ramping up activation for more powerful strikes against tougher wood
Woodpeckers have adopted the same breathing technique used by professional tennis players. Both exhale through the moment of impact. Research reveals these birds forcefully breathe out with every strike of their bill against wood, using a respiratory pattern that likely stabilizes their core during forceful pecking.
Scientists at Brown University discovered that downy woodpeckers maintain airflow while drilling. They coordinate exhalation with each peck in a pattern remarkably similar to the grunting athletes use when serving a tennis ball or lifting heavy weights. This respiratory strategy increases air pressure inside the body, stiffening the torso and potentially creating a more stable platform for forceful strikes.
The finding challenges assumptions about how woodpeckers manage hammering trees. Rather than bracing against impact by closing their airways, these birds keep air flowing while contracting their abdominal muscles to spike internal pressure at precisely the right moment.
The Science Behind the Woodpecker Grunt
Nicholas Antonson, lead author of the study published in the Journal of Experimental Biology, used electromyography to measure muscle activity in eight downy woodpeckers as they drilled wood. His team recorded changes in air-sac pressure and breathing patterns, syncing these measurements with high-speed video to capture the exact timing of each behavior.
Abdominal muscles contracted in two distinct bursts during each peck. The first occurred as the bird swung its head forward toward the wood. The second happened at the moment of contact, coordinating with a rise in expiratory pressure around impact, with a brief dip exactly at contact.
This pattern mirrors what happens when tennis players grunt during a serve. They forcefully exhale while contracting their core muscles, and studies show this technique measurably increases ball velocity without raising oxygen costs. The mechanism stiffens the spine and torso to provide a more stable base for generating power.
Woodpeckers appear to use a similar principle. By exhaling forcefully at impact while pressurizing their air sacs and contracting abdominal muscles, they likely create rigidity throughout the body precisely when the bill strikes wood.
To confirm that woodpeckers maintained airflow during drilling, researchers inserted tiny thermistor probes into the trachea of two birds. These probes detected continuous airflow during drilling, proving the airways remained open during pecking. This contrasts sharply with behaviors like defecation, where woodpeckers close their airways to pressurize the thoracic cavity, similar to the Valsalva maneuver used during heavy lifting.
Mini-Breaths at Lightning Speed
The breathing strategy persisted even during rapid tapping, where birds struck wood at rates reaching up to 13 times per second. Remarkably, individuals synchronized respiration with each strike in a perfect one-to-one ratio, taking miniature breaths between successive pecks. These inspirations could be as brief as 40 milliseconds, meaning respiratory rates increased from roughly three breaths per second at rest to approximately nine breaths per second during tapping.
The mini-breath pattern closely resembles respiratory strategies in songbirds. Many bird species take quick inspirations between vocal phrases during songs, allowing them to maintain long singing bouts. The discovery that woodpeckers use similar mini-breaths during non-vocal behavior suggests this respiratory adaptation may have broader evolutionary origins than previously recognized.
A Whole-Body Hammer
Beyond breathing, the study revealed that drilling engages muscles throughout the entire woodpecker body. Eight different muscle groups spanning the head, neck, abdomen, hips and tail activated in precisely timed sequences during each peck. Neck muscles contracted to create a stiffened lever arm, hip muscles powered forward movement, and tail muscles braced against the tree.
This whole-body coordination transforms the bird into a biological hammer. The head and bill function as the hammer head, while the stiffened neck serves as the handle. Hip muscles provide the swing force, and the tail anchors the body against recoil.
The hip muscle showed particularly interesting behavior, activating more intensely during hard pecks compared to soft pecks. This suggests hips play a key role in modulating drilling power.
During sequences of rapid tapping, most muscles progressively increased their activation across successive strikes, likely compensating for cumulative fatigue while maintaining consistent strike force and timing. Two neck muscles, however, maintained steady activation throughout, possibly serving postural stabilization roles.
Future studies may investigate whether this coordination changes during drumming displays, where woodpeckers strike substrates at even higher frequencies than the tapping behaviors examined here. The work also raises questions about how woodpeckers learn to coordinate breathing with drilling. Young birds must somehow develop the neural connections and timing precision needed to synchronize abdominal contractions, exhalation, and bill strikes.
Paper Summary
Methodology
Researchers implanted fine-wire electromyography electrodes into eight different muscles spanning downy woodpecker bodies, including four neck and head muscles (longus colli ventralis, longus colli dorsalis, flexor colli lateralis, and musculus complexus), one abdominal muscle (musculus obliquis externus abdominus), two leg muscles (iliotibialis cranialis and iliofibularis), and one tail muscle (musculus depressor caudae). They fitted flexible silicone cannulas into the anterior thoracic air sac of six birds to measure respiratory pressure changes. In two individuals, they also mounted microbead thermistors above the syrinx to track tracheal airflow direction and magnitude. All physiological recordings were synchronized with high-speed videography at 250 frames per second, achieving temporal precision within four milliseconds. Birds performed drilling and tapping behaviors voluntarily in laboratory chambers equipped with wooden substrates while researchers recorded muscle activity, breathing patterns, and behavioral kinematics. The study examined three behavioral contexts: baseline rest, head rotation, soft pecks, hard pecks, and repetitive tapping sequences. EMG signals underwent bandpass filtering, rectification, and smoothing to create amplitude envelopes for analysis. Root mean square values quantified overall muscle activation intensity for comparisons across behaviors.
Results
All eight muscles examined showed significantly higher activation during drilling compared to baseline resting states and head-turning movements. Muscles activated in coordinated temporal sequences aligned with different phases of the pecking cycle. The longus colli ventralis, musculus obliquis externus abdominus, musculus depressor caudae, and iliotibialis cranialis peaked in activity during head protraction, before bill contact. The longus colli dorsalis, musculus complexus, flexor colli lateralis, and iliofibularis showed maximum activation at or immediately after the moment of impact. Only the iliotibialis cranialis showed differential recruitment between soft and hard pecks, with significantly greater activation during harder strikes. Respiratory pressure increased sharply during head protraction, showed a brief dip at the exact moment of impact, then rose again during retraction. Tracheal airflow measurements confirmed syringeal valves remained open throughout drilling, contrasting with defecation where valves closed. During rapid tapping, birds struck wood at rates up to 13 times per second across recorded sequences. Woodpeckers maintained one-to-one coordination between pecks and respiratory cycles, taking mini-breaths that could be as brief as 40 milliseconds between strikes. Respiratory rates during tapping reached approximately nine breaths per second, compared to the resting rate of 2.8 breaths per second. Most muscles showed progressively increasing EMG amplitude across successive taps in a sequence, though activation timing remained consistent. The longus colli ventralis and flexor colli lateralis maintained stable activation levels across taps.
Limitations
The study examined only downy woodpeckers, a relatively small species weighing less than 30 grams. Larger woodpecker species may show different patterns of muscle recruitment and respiratory coordination. Birds performed behaviors in controlled laboratory settings on a single wood substrate type, which may not fully represent the range of mechanical demands encountered during natural foraging, excavation, and territorial drumming. The sample size varied across muscles, with three to four individuals per muscle group, limiting statistical power for some comparisons. Researchers recorded activity from eight muscles but many additional muscles likely contribute to drilling behavior. The study focused primarily on drilling and tapping rather than territorial drumming, which occurs at even higher frequencies. EMG amplitude provides a proxy for muscle force production but cannot directly measure actual forces generated. Electrode placement variability between individuals prevented direct comparisons of activation intensity across different muscles. The study did not examine how coordination patterns develop during ontogeny or how they vary across individuals of different age, sex, or competitive ability.
Funding and Disclosures
This research received support from National Science Foundation grants PRFB-2305848 (to Nicholas Antonson), IOS-2423144, and DBI-2150328 (to Matthew Fuxjager). The authors declared no competing or financial interests. All work received approval from the United States Fish and Wildlife Service, Rhode Island Department of Environmental Management, and Brown University Institutional Animal Care and Use Committee (protocol number 23-01-1001). Data and analysis code are publicly available via figshare at doi:10.6084/m9.figshare.29469872.
Publication Details
Antonson ND, Ogunbiyi S, Champigneulle M, Roberts TJ, Goller F, Fuxjager MJ. 2025. “Neuromuscular coordination of movement and breathing forges a hammer-like mechanism for woodpecker drilling,” was published November 6, 2025 in the Journal of Experimental Biology 228: jeb251167. doi:10.1242/jeb.251167
