Decoding the chaffinch "rain" call: A female-directed alarm call?
Data files
Jun 02, 2025 version files 71.80 KB
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BehaviouralObservations.Rmd
837 B
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BehavouralObservation_data.csv
6.74 KB
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PredatorPlaybackAnalysis.Rmd
3.24 KB
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PredPlayback_data.csv
8.82 KB
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RCplayback_perphase.csv
37.59 KB
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RCPlayback_summary.csv
3.68 KB
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README.md
7.77 KB
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TerritoryPlaybackAnalysis.Rmd
3.12 KB
Abstract
Acoustic communication is vital for many animal taxa. Many songbirds have elaborate communication systems and large vocal repertoires consisting of learned, complex songs, and calls that are usually simpler in structure. While the functions of songs have been well researched, the functions of bird calls is often difficult to deduce from the context. A well-known example is the “rain” call of the common chaffinch (Fringilla coelebs): although chaffinches are very common and “rain” calls are conspicuous and frequent, the function of this call is still a mystery. It has been proposed to serve such diverse functions such as song substitute in territorial contests, predator alarm call, or within-pair coordination. Here, we systematically tested these hypothesized three functions, using a combination of two playback experiments and field observations. We found that chaffinches did not react to “rain” call playbacks with the same aggressive behavior as to song playbacks. Predator vocalizations, however, consistently elicited “rain” calls. In addition, when a female was visible, male chaffinches used “rain” calls more often both during predator simulation and in the actual presence of predators. Since the “rain” call is only uttered during the breeding season and it is associated with the presence of a female and predators, we propose that the “rain” call is a specific alarm call used in the context of defense against nest predators.
Dataset DOI: 10.5061/dryad.j9kd51cqm
Description of the data and file structure
The chaffinch Fringilla coelebs is a very common passerine in Europe. One of the chaffinches' vocalizations, called "rain-call", is very common and conspicuous, however, its function is still not well understood. Three hypotheses have been postulated as to what chaffinches rain-call are for: (1) the rain-call could be used in territorial context by males as a substitute for the song when the bird is in stressful conditions, (2) the rain-call is an alarm call, and (3) the rain-call is a mate-directed signal for communication within the pair. We tested these three hypotheses using two playbacks and behavioural observations in the wild.
- In the first playback, we broadcasted rain-calls, chaffinch songs and the song of blackbirds as a control. We measured if chaffinch males reacted to rain-calls similarly to a simulated territorial intrusion.
- In the second playback, we simulated the presence of predators (hawk and crows, compared to a blackbird's song as a control) and observed if chaffinches started rain-calling.
- Third, we closely followed five chaffinch males in the field, and took good note of the social and environmental context of rain-calling behaviour.
We find that chaffinches did not react to rain-calls with the same aggressive response than to territorial intrusion, which does not support the hypothesis of a song substitute. We found that chaffinches started rain-calling consistently when we broadcasted predator calls, as well as when we saw real predators, which supports the alarm call hypothesis. Finally, we found that male chaffinches rain-called much more often when a female chaffinch was around, which might hint that females are intended receivers of the rain-call alarm.
We provide here the complete dataset for all three experiment as well as the R code used to run statistical analyses. Variables and software versions are described further.
R scripts have been run with R version 4.2.2, 2023.
package versions:
bayespot 1.10.0
tidyverse 2.0.0
ggeffects 3.4.1
rstan 2.32.6
rstanarm 2.32.1
Files and variables
File: RCplayback_perphase.csv
Description: data from the territory playback with behavioural responses split per playback phase (before, during and after broadcast)
Variables
- ID: Identifier of the territory where the playback was performed
- Latitude: Latitude (degree)
- Longitude: Longitude (degree)
- Date: Date of experiment (YYYY-mm-dd)
- Time_end: Time at the end of the playback experiment (HH:MM)
- PB_type: Playback type (Raincall, song or blackbird control)
- PB_phase: Phase of the experiment (before playback broadcast, during broadcast or after)
- Distance_initial: Distance (m) between the bird and the loudspeaker at the start of playback broadcast
- Distance_initial_scaled: Initial distance centered on XX
- PB_amplitude: Playback amplitude at 1m (dB (A))
- PB_amplitude_scaled: Playback amplitude centered on the mean per playback type and standardized by 6 dB
- Time_to_playback: Time (seconds) between the end of the initial 3-minute observation period and the start of playback
- Time_to_playback_scaled: Time to playback centered on the mean
- Female_YN_total: Female visible (yes) or absent (no) during the experiment
- N_song_3: Number of complete songs (with flourish)
- N_flight: Number of flights
- N_pink: Number of "pink" / "chink" alarm calls
- N_rain_call: Number of rain-calls
File: RCPlayback_summary.csv
Description: data from the territory playback
Variables
- ID: Identifier of the territory where the playback was performed
- PB_type: Playback type (Raincall, song or blackbird control)
- Time_to_playback: Time (seconds) between the end of the initial 3-minute observation period and the start of playback
- Time_to_playback_scaled: Time to playback centered on the mean
- PB_amplitude: Playback amplitude at 1m (dB (A))
- PB_amplitude_scaled: Playback amplitude centered on the mean per playback type and standardized by 6 dB
- Distance_initial: Distance (m) between the bird and the loudspeaker at the start of playback broadcast
- Distance_initial_scaled: Initial distance centered on the mean
- Female_YN_total: Female visible (yes) or absent (no) during the experiment
- Rain_call_YN_before: Presence (1) or absence (0) of raincalls during the 3-minute observation period before the start of playback broadcast
- Rain_call_YN_during_after: Presence (1) or absence (0) of rain-calls after the start of playback broadcast
- Latency_approach: Latency (seconds) between the start of playback broadcast and first flight towards teh loudpeaker
- Approach_YN: Did the bird approach (1) the loudspeaker after the start of playback broadcast or not (0)
- Distance_min: Minimum distance (m) between the bird and the loudspeaker
File: TerritoryPlaybackAnalysis.Rmd
Description: R code used perform statistical analyzes of the territory playback
File: BehaviouralObservations.Rmd
Description: R code used to run the statistical models on the behavioural observations
File: BehavouralObservation_data.csv
Description: data from the behavioural observations
Variables
- ID: ID of the territory
- Session_nr: ID of the 10-minute observation block
- Rain_call_presence: presence (1) or absence (0) of at least one rain-call during the 10-minute block
- Female_YN_proportion: number of minutes during the 10-minute blocks where a female was visible to the observers
- Predator_YN_proportion: number of minutes during the 10-minute blocks where a chaffinch predator (hawk or crow) was visible to the observers
- Male_YN_proportion: number of minutes during the 10-minute blocks where another chaffinch male was heard singing
- Time_dec_block: time (hours) relative to midnight of the start of the ten-minute block
- Time_dec_block_scaled: time (hours) relative to midnight of the start of the ten-minute block centered on 10 (the approximate median time of observation)
File: PredatorPlaybackAnalysis.Rmd
Description: R code used to perform statistical analysis on the playback of predator calls
File: PredPlayback_data.csv
Description: data from the predator call playback
Variables
- Bird_ID: Identifier of the territory where the playback was performed
- Lat_deg: Latitude (degree)
- Long_deg: Longitude (degree)
- Day: Day of experiment
- Month: Month of the experiment
- Hour: Hour of the broadcast
- Min: Minute of the experiment
- Tim_rel_sunrise: Time (hours) relative to sunrise
- Playback: Playback type (control, hawk or crow)
- DistInit_m: Distance between (m) the bird and the loudspeaker at the start of playback broadcast
- DistInit_st: Distance between the bird and the loudspeaker at the start of the playback, centered and standardized
- Ambient_Noise_dBA: Peak LAf ambient noise (dB(A))
- Noise_st: Ambient noise centered on the mean and standardized by 6 dB
- Female: Female visible (present) or not (absent) during the playback
- Factivity: Flight activity (number of flights per minute)
- Sactivity: Song activity (number of songs per minute)
- RC: Presence (present) or absence (absent) of at least one rain-call during the playback
- T2RC: Latency (seconds) until the first rain-call was heard. set to 360 (max duration of playback) if no rain-call heard
- RC_rate: Number of rain-call per minute after the first rain-call was heard
- Time_left: Number of seconds during which we sampled the number of rain-calls (shorter if the first rain-call occured during after the predator
