The Wilson’s snipe (Gallinago delicata) is a medium-sized shorebird found across North America. It is best known for the unique winnowing sound males make during their mating displays in spring. The snipe’s flight feathers have evolved to produce this distinctive sound when air rushes through them during rapid dives and climbs. Understanding the acoustics behind the Wilson’s snipe’s winnowing sound provides insight into the ecology and behavior of this fascinating bird.
What causes the winnowing sound?
The Wilson’s snipe winnowing sound is produced by air rushing through the bird’s outermost tail feathers during a fast, steep dive. As the snipe dives, it spreads its tail into a broad fan shape. The tail feathers are narrow, stiff, and ridged, causing the air to vibrate as it flows over them. This vibration creates the pulsing, bleating sound that carries over long distances.
While diving, the snipe reaches speeds of 60-70 mph. It is the combination of speed, vibrating tail feathers, and the vacuum created behind the spreading tail that generates the loud, carrying winnowing sound. The entire tail functions like a musical reed instrument. By changing the position of its tail, the snipe can modulate the sound to create variations in pitch and volume.
When and why do snipes make the winnowing sound?
In spring, male Wilson’s snipes perform aerial displays high above the ground to mark and defend their breeding territories. The winnowing sound advertises the male’s presence to competitors and potential mates.
Snipes winnow frequently in the evening and early morning hours when sound carries well in the still, moist air. Cool, humid conditions may also facilitate sound transmission. A single display bout may last up to 30 minutes as the snipe dives and swoops again and again.
The winnowing sound is thought to play several roles:
- Proclaiming ownership of a territory
- Warning rival males to stay away
- Alerting females to the male’s location
- Signaling the performer’s fitness as a mate
Females seem to be drawn to the most frequent and prolonged winnowing displays. These are indicators that the male can energetically sustain elaborate courtship flights and has the endurance to protect a good territory.
What does the winnowing sound resemble?
The Wilson’s snipe’s winnowing has been poetically described as resembling the bleating of a nimble goat, a pneumatic drill, or a throbbing engine. The pulsing, tremolo sound is unique and difficult to reproduce. The quavering, wailing notes waver in pitch and volume as the snipe dives and swoops erratically.
Listeners often describe the winnowing as similar to these sounds:
- The wavering wail of a newborn infant
- The vibrating “brrrr” of lips fluttering
- The throbbing hum of an engine gaining power
- The pulsing buzz of an electric razor
- The bleating mew of a hungry kitten
- The whirring of vinyl records fast-forwarding
The snipe’s vocalizations are outside the range of human speech and song. The quavering, tremolo effect stems from rapid frequency modulations too fast for the human ear to track. This gives the winnowing an otherworldly, pulsating quality.
How far can the winnowing sound carry?
The Wilson’s snipe’s winnowing display is one of the loudest sounds produced by any North American shorebird species. Measured at close range, the winnowing registers around 93 decibels – similar to the noise level of a lawn mower.
This loud bleating sound can carry up to 1 mile on calm days, allowing the male snipe to advertise across a large territory of wet meadows and marshes. The winnowing may be audible up to 2-3 miles away with helpful wind and weather conditions:
- Wind direction – Sound propagates farther when blowing towards the listener.
- Humidity – Moist air conveys sound better than dry air.
- Temperature – Cool air transmits sound better than warm air.
- Surrounding landscape – Open terrain enables farther propagation.
Concentrating displays around dawn and dusk may also help the winnowing carry farther under atmospheric conditions that favor sound transmission.
How do snipes produce such loud winnowing sounds?
Wilson’s snipes maximize the volume of their winnowing display in several key ways:
- Swift flight – By diving at 60-70+ mph, the snipe creates more air turbulence over its tail.
- Spread tail – Fanning out the tail feathers increases surface area for sound generation.
- Stiff feathers – Narrow, ridged feathers vibrate more efficiently in airflow.
- Tremolo effect – Rapid modulations magnify the loudness humans perceive.
- Repeated dives – Making many consecutive dives sustains the sound level.
- Resonant cavities – Skull sinuses may amplify internally generated sounds.
This combination of anatomical, aerodynamic, and behavioral adaptations allows the male snipe’s winnowing bleats to reach impressively far distances.
How do snipes achieve such fast dives?
Wilson’s snipes are able to power sustained 60-70 mph plunges thanks to several key adaptations:
- Compact, muscular body – Provides strength and agility for maneuvers.
- Long, narrow wings – Generate less drag and turbulence in fast flight.
- Lightweight skeleton – Aids in acceleration and high speeds.
- High wingbeat frequency – Up to 26 beats per second during display dives.
- Fast-twitch breast muscles – Allow powerful bursts of flight.
- Steep dive angle – Reaches over 60° before pulling out; trades height for speed.
Together, these traits enable the snipe to make the near-vertical power dives needed to produce loud winnowing sounds. This fast, acrobatic flight performance demands top fitness to attract mates.
How does snipe wing anatomy contribute to winnowing?
| Wing Feature | Contribution to Winnowing Sound |
|---|---|
| Long primary feathers | Increase surface area contacted by air |
| Stiff vanes on outer primaries | Vibrate efficiently like reeds |
| Serrated outer vane edges | Turbulence enhances fluttering |
| Thin, tapered profile | Cuts through air cleanly |
| Slight backward curve | Catches airflow at steep dive angles |
The snipe’s outer primary wing feathers act as specialized sound generators. Their length, narrowness, stiffness, and serrated edges all enhance the fluttering, turbulence, and vibration that creates winnowing sounds in fast moving air.
How do snipes control variations in winnowing sounds?
Wilson’s snipes can modulate their winnowing display by adjusting:
- Dive speed – Faster dives mean louder, higher-pitched sound.
- Dive angle – Steeper angles equal more speed and higher notes.
- Tail spread – Wider tails give louder, more turbulent sound.
- Tail angle – Adjusting pitch spreads air impact across tail.
- Wing stiffness – Relaxing wings dampens flutter for softer sound.
- Throat tension – May change resonance in skull/bill cavities.
Subtle shifts in speed, angle, feathers, and resonance allow snipes to create an intricate range of sounds, conveying information to listeners. Females may gauge male fitness by the ability to sustain complex winnowing displays.
How do female snipes respond to winnowing displays?
When a female snipe hears a sustained winnowing display, she may fly toward the sound to inspect the male more closely. If she approves of the male’s fitness on the basis of his display, she may allow him to lead her to suitable nesting habitat in his territory.
Research suggests female snipes respond more strongly to:
- Louder, more consistent winnowing
- More rapid dive sequences
- Longer display bout duration
- Earlier and later displays in the day
These traits indicate a healthier male able to provide robust breeding opportunities. The female invites copulation by squatting in the nesting area. After breeding, she leaves the male’s territory to incubate eggs and raise chicks alone.
Can differences in winnowing identify individual snipes?
The winnowing sound is highly variable between dives, birds, locations, and days. However, researchers have discovered consistent individual differences that may allow snipes to identify known neighbors vs. strangers:
- Maximum frequency
- Minimum frequency
- Frequency range
- Fundamental frequency
- Peak frequency
- Number of pulses
- Pulse rate
Measurable characteristics like pitch, pulse number, and frequency parameters create a sound signature for each male snipe. Familiar local males may be distinguished from intruding strangers by winnowing alone.
How do snipes develop their elaborate winnowing displays?
Wilson’s snipe winnowing ability likely involves both innate instinct and learned experience:
- Male snipes winnow spontaneously on migration before breeding.
- Hand-raised snipes winnow without exposure to adults.
- But displays increase after exposure to adult winnowing.
- Older males perform more elaborate and consistent displays.
Young snipes seem to possess innate instructions to winnow. But performance improves with practice and feedback from other snipes’ winnowing sounds. Full display proficiency takes time to perfect through each breeding season.
How may climate change affect snipe winnowing?
Sustained global warming and shifting weather patterns could impact Wilson’s snipe displays:
- Earlier spring migration and breeding onset
- Northward expansion of breeding range
- New climate constraints on optimal display habitats
- Changes to humidity, wind, and temperature affecting sound transmission
If climate shifts decrease suitable display conditions, snipe winnowing patterns and success may decline. Continuous monitoring will reveal how this keystone sound of the marshes adapts to climatic transformations.
Conclusion
The Wilson’s snipe’s haunting winnowing sound provides a excellent example of evolution crafting specialized structures and behaviors for maximum acoustic effect. Sexual selection has honed anatomical traits from feathers to muscles to enable challenging mating displays that advertise male quality. The enigmatic bleating created by air rushing through vibrating feathers conveys vital information to competing males and discerning females. Even in a changing climate, the snipe’s winnowing will continue to evoke the mystery and allure of birdsong. Careful study of this display offers insights into the ecology and evolution of avian communication.
