DOI: 10.5061/dryad.j9kd51cqm
title: Decoding the chaffinch "rain" call: A female-directed alarm call?

description: 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.
description: # Decoding the chaffinch "rain" call: A female-directed alarm
 call? Dataset DOI: [10.5061/dryad.j9kd51cqm](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