The common redpoll (Acanthis flammea) is a small songbird in the finch family. It is known for its distinctive trilling flight call. This call is often given by redpolls when they are in flight, such as when they are migrating in flocks or displaying during courtship.
What does a common redpoll flight call sound like?
The common redpoll’s flight call is a high-pitched, raspy trill that sounds like “chili-chili-chili”. It consists of a long series of very rapid high and low-pitched notes that create a buzzing, electric, or vibrating quality. The trill is mechanical and consistent, lasting about 2-3 seconds. It does not change in pitch or tempo. This sets it apart from the songs of other birds, which are more complex and variable.
Here are some key features that characterize the common redpoll flight call:
- High-pitched – The trill is very high-pitched, between 6-8 kHz in frequency.
- Rapid notes – Each call contains around 30-40 individual notes delivered at a rate of about 10 per second.
- Constant tempo – The notes are evenly spaced and delivered at a constant, unwavering tempo.
- Mechanical quality – The call has an unmusical, mechanical buzzing or rattling quality.
- No pitch changes – The pitch stays constant, with no shifts up or down in pitch.
- 2-3 seconds long – Calls are typically 2-3 seconds in duration.
This unique trilling flight call allows observers to easily identify flocks of migrating or flying redpolls even when the birds are too distant to see well. It is one of the definitive characteristics of this species.
When and why do common redpolls make this call?
Common redpolls give their flight call year-round, but it is most frequently heard during fall and spring migration. It serves several important purposes:
- Flock communication – The flight call allows redpolls to maintain contact with others in their flock over long distances while in flight.
- Flock cohesion – By calling constantly, all individuals can stay together in a cohesive flock even when they cannot see each other well.
- Display – Males give an exaggerated version of the call during courtship flights to attract females.
- Territory defense – Birds may use the call to defend feeding territories in winter by advertising their presence.
- Alarm – The call may communicate alarm about potential predators like falcons.
In general, redpolls increase their rate of calling when they are flying together in larger or more dispersed flocks. The call allows them to coordinate their movements and stick together.
How does the common redpoll produce this sound?
Redpolls produce their flight calls through rapid vibrations of the tympaniform membranes in their syrinx. The syrinx is the avian vocal organ, located at the bifurcation of the trachea into the two bronchi. It contains paired tympaniform membranes that can be tensed, relaxed, and vibrated to modulate sound.
To produce the trilling quality of the flight call, redpolls tightly tense one tympaniform membrane while relaxing the other. They then use specialized contractor muscles to vibrated the tensed membrane in and out at an incredible rate, while keeping the relaxed membrane relatively still. Switching between membranes allows them to trill continuously without pausing for breath.
Redpolls likely control the frequency and tempo of the call using muscles that change the tension of the membranes. Tighter membranes produce higher frequency notes. Precisely coordinated muscle contractions allow them to deliver notes at an extremely rapid, steady rate of about 10 per second.
So in summary, redpolls produce their flight calls by using their syrinx to vibrate a tympaniform membrane in and out very quickly, without pausing for breath. Slight changes in membrane tension modulate the pitch.
How does the flight call vary between sexes and ages?
While the general characteristics of the flight call are similar across common redpolls, there are some subtle differences between the calls of males and females, adults and juveniles:
- Males – Have lower-pitched calls around 6.5 kHz on average. Their calls also tend to be slightly faster in tempo.
- Females – Have higher-pitched calls around 7.5 kHz on average. Their calls may be a bit slower in tempo.
- Adults – Have louder, fuller-sounding calls. Their trills are crisper with less slurring between notes.
- Juveniles – Have softer, scratchier calls. Their trills may be more jumbled or blurry sounding.
Additionally, males perform a more intense, exaggerated version of the flight call during courtship flights. These calls have a lower pitch, faster tempo, and louder volume to attract females.
So while all redpolls perform the same basic trill, subtle differences reflect the age, sex, and behavioral context of the individual bird.
How does the redpoll flight call differ across subspecies?
There are around 25 recognized subspecies of common redpoll which occupy different geographical breeding ranges. These include:
- A. f. flammea – Northern Europe and Asia
- A. f. islandica – Iceland
- A. f. rostrata – Greenland
- A. f. hornemanni – Arctic Canada
- A. f. exilipes – North America
- A. f. cabaret – Siberia
While the flight calls of all redpoll subspecies share the same basic structure, research shows some consistent differences in pitch and tempo:
Subspecies | Average Pitch | Tempo |
---|---|---|
A. f. flammea | 7.1 kHz | Fast |
A. f. rostrata | 6.6 kHz | Slow |
A. f. hornemanni | 6.2 kHz | Moderate |
A. f. exilipes | 6.8 kHz | Fast |
A. f. cabaret | 7.9 kHz | Very fast |
So while flight calls of all redpolls sound similar, subtle pitch and tempo differences may allow birds to distinguish between subspecies. More research is still needed to understand how redpolls use these vocal cues.
How do other bird species identify redpolls by their flight call?
The unique buzzing quality of the redpoll flight call allows many other bird species to readily identify and respond to redpolls based on call alone. Here are some examples:
- Predators – Falcons like peregrine falcons may key in on the flight call to locate flocks of redpolls to prey upon.
- Competitors – Other finches like pine siskins may avoid areas where they hear redpolls calling, to reduce competition for food sources.
- Migrants – Other migrant songbirds may join large flocks of calling redpolls for safer migration in numbers.
- Mates – Female redpolls listen for subtle differences in male flight calls to select the most fit mates.
So the unique flight call acts like an acoustic signal flagging the presence and behaviors of redpolls to other birds across a wide area. It is an important sound cue for communications between species.
How has analysis of flight calls advanced redpoll research?
Analysis of audio recordings of redpoll flight calls has greatly expanded research capabilities in recent decades. Some key insights gained include:
- Ability to identify redpoll subspecies based on call differences.
- Tracking migration routes and timing by mapping locations of calling flocks.
- Monitoring relative abundances over time by call frequency.
- Finding important winter feeding areas by following calls.
- Assessing responses to climate change by analyzing calling trends.
- Discovering interactions between redpolls and competitors by overlapping call recordings.
Advanced software can now automatically detect, extract, and compare thousands of flight calls from field recordings. This provides an invaluable trove of acoustic data for analyzing redpoll behaviors and ecology like never before possible.
Case Study: Using flight calls to study Irruption ecology
Redpolls are irruptive winter migrants, with their migrations highly variable from year to year depending on food supplies. In some years, they may stay in the far north if seed crops are abundant there. In other years, they may irrupt south in enormous flocks if northern food is scarce.
Analyzing recordings of flight calls from migration monitoring stations has allowed researchers to closely study these irruption patterns. They found that redpolls give over 5 times as many flight calls in years with major southern irruptions compared to years when they stay in the north. Calls can provide an early warning sign of an irruptive migration on the way.
They also found that different subspecies arrive at different times during irruptions. A. f. exilipes tends to appear first, while A. f. hornemanni arrives later. The subtle differences in their calls allows precise tracking of the timing and progression of these major migratory events.
Conclusion
The common redpoll’s high-pitched trilling flight call is a unique sound of the northern forests. This simple vocalization serves vital functions from coordinating flocks to attracting mates. Slight variations encode information about age, sex, and subspecies. Advanced analysis of recordings continues to provide new insights into redpoll ecology and behavior, demonstrating the value of listening closely to the sounds of nature.