DOI: 10.5061/dryad.0vt4b8h5n
title: Familiarity, homogeneity, and discrimination of song dialects: Data and playback study stimuli

description: Male songbirds of many species sing local song dialects that are
 restricted to defined geographical areas. In most tests of responses to
 local versus foreign dialects, males respond more aggressively to songs
 from their own dialect, presumably because local males represent more of a
 threat to their success. We asked how hearing foreign songs during
 development and territory establishment affects discrimination of the
 local dialect in wild Savannah sparrows, Passerculus sandwichensis. After
 foreign songs had been heard from loudspeakers in the study area in at
 least two consecutive breeding seasons, males reduced the intensity of
 their responses to the local version of population-specific buzz segment
 of the song. Four years after the foreign songs were last broadcast on the
 study area, males again responded more aggressively to the local version
 of the buzz. As for the basis of these responses, we found no evidence
 that birds discriminated among dialects by comparing them to their own
 songs. However, auditory experience with a foreign song, whether during
 song development (from speaker-simulated song tutors) or during the
 current breeding season (from neighbours’ songs), reduced the intensity of
 birds’ responses to the local buzz type. Both familiarity, in the form of
 auditory experience with a song type, and homogeneity, when a song type is
 sung by all or nearly all of the population, appear to contribute to
 heightened aggressive responses to a local song dialect.
description: The songs of Savannah sparrows <em>(Passerculus
 sandwichen</em>sis) in the Grand Manan archipelago (New Brunswick,
 Canada) were recorded using a Marantz digital recorder (PMD670 or PMD660)
 and a Sennheiser ME-66 directional microphone; our digital recordings used
 a 44 kHz rate and a 16-bit depth. We also used some songs recorded between
 1993 and 2011 to characterize Kent Island variant buzzes and generate
 stimuli for buzz playbacks (see Wheelwright et al., 2008 for details on
 methods for those recordings). We digitized songs originally recorded on
 tape using SoundEdit Pro (Macromedia; 44 kHz and 16 bits). 
 The buzz segments of all songs and stimuli used in this study
 were characterized by measuring their mean frequency (using
 SoundAnalysisPro; Tchernichovski et al., 1999; http://soundanalysispro.com) and pulse duration (buzz duration divided by the number of repeated sound pulses). These two parameters are sufficient for distinguishing the different dialects of Savannah sparrow buzzes (see Williams et al, 2019). Stimuli used in playback studies were buzz segments drawn from four different Savannah sparrow song types: (1) the local Kent Island dialect, (2) a variant that was no longer sung on Kent Island, (3) a dialect from Williamstown, MA, USA, 500 km distant, and (4) songs from western North America that were broadcast through speakers on Kent Island from 2013-2018 and were learned by some local birds (see Mennill et al., 2018). Each set of four stimuli (one of each type) was matched for duration and amplitude. Subjects of playback studies included (1) birds breeding on Kent Island in 2012; (2) birds breeding on Kent Island in 2016 and 2017 (3) birds breeding on nearby islands in 2016, and (4) birds breeding on Kent Island in 2022. The second category, birds breeding on Kent Island in 2016 and 2017, heard foreign songs broadcast from speakers on their breeding site, and some of them had copied those songs. All subjects were mated males. A playback session consisted of a primer stimulus, which was a song in which the buzz had been replaced with silence, which was used to try to minimize first-stimulus effects, followed by the four stimulus types deiivered in a varied, balanced order. Each stimulus was played for two minutes (5 buzzes per minute). Response duration was measured as the time between the end of the stimulus playback and the time when the subject ceased to respond aggressively (either  and the time when the male ceased to respond was noted. Responses to the playback were scored as ending when a bird either sang a full, loud song; began foraging; started preening; or flew more than 30 meters away from the speaker. We used this measure because individual birds used different aggressive behaviors when responding to a playback (see Williams et al., 2019). These responses were evaluated by GLMM models that included stimulus order, stimulus type, subject identity, acoustic similarity of the stimulus to the subject's own buzz, and the subjects' experience with foreign songs (during development and during the season of the playback study). Data files include the acoustic measurements of different buzz types; responses to playback stimuli; and an R script recapitulating the analyses reported in the paper. Also included are four sound files that include eight versions of each of the different buzz types used as playback stimuli.
description: # Familiarity, homogeneity, and discrimination of song dialects: Data and
 song stimuli The buzz
 segment of Savannah sparrow songs is generally consistent within a
 population, but varies across populations. Variation occurred within the
 Kent Island (New Brunswick, Canada) population in two ways: between 1994
 and 2004 a total of 19 males sang a variant buzz that has not been sung
 since, and between 2013 and 2018 foreign (Western) songs were broadcast
 from speakers on the study site and were copied by some birds during song
 development. The paper associated with this data set assessed responses to
 local and foreign dialects using four buzz. By comparing the acoustic
 characteristics of each bird's buzz to those of the stimuli it heard,
 we were able to show that the intensity of a bird's response is not
 predicted by the acoustic difference between his song and the stimulus. We
 found that responses to the local dialect depend on a bird's
 experience both during development and during the current breeding season,
 and that only when the dialect features within a song are both familiar
 and homogeneous (sung by nearly all the birds in a population) do the
 birds respond more aggressively to the local dialect than to a foreign
 dialect. When the local dialect is not homogeneous, responses fall to the
 same level as those given to unfamiliar dialects and to minority dialects
 present on the study site. ## Description of the data and file structure
 **Acoustic characteristics of different buzz types and stimuli** (2 csv
 files). 1\)  ForeignWtnKIBuzzes.csv has the measurements of acoustic
 characteristics for buzz segments from 362 Savannah sparrow songs. A total
 of 222 songs were drawn from recordings made on Kent, Grand Manan, and
 White Head islands in the Bay of Fundy, New Brunswick, Canada. A total of
 94 songs were recorded 500 km away in Williamstown,Massachusetts, U.S.A.,
 and 46 foreign songs from Western North America songs were broadcast
 through speakers on the Kent Island study site from 2013-2018. The bird or
 recording identity, the buzz type, and the year are given in the first
 three columns. The next three columns provide the song type, and that type
 indexed by numbers so that the file can be sorted appropriately for
 graphing. We had previously found (Williams et al., 2019,
 ) that buzz dialects could be characterized
 by mean frequency and pulse period, so we used those two measurements for
 analysis. For each buzz, frequency (Hz)and buzz duration (ms) measurements
 obtained using Sound Analysis Pro (Tchernichovski et al., 2000,
 [10.1006/anbe.1999.1416](http://dx.doi.org/10.1006/anbe.1999.1416)) are
 included. We counted the number of pulses and used that and the duration
 to derive the pulse period (ms). For 28 of the 363 birds, only these two
 critical variables were measured; for the remaining birds, additional
 variables as measured by Sound Analysis Pro are available upon request to
 the corresponding author.  2\)  PBstimulussubjects_2016-7.csv includes the
 duration (ms), mean frequency (Hz), peak frequency (Hz), number of pulses
 (count), and pulse period (ms) for the buzzes of all stimuli and subjects
 used in 2016-2017 on Kent Island and Grand Manan Island. The first two
 columns in each row give the bird identity and the location or stimulus
 type of the buzz. The third column designates the song type so that the
 file can be sorted appropriately for figures. **Examples of buzz types and
 stimuli** (4 WAVE files) 1\)  Kent Island stimuli.wav includes the eight
 stimuli of this category used in 2016-2017 (none were derived from songs
 sung by any of the subjects). All have high mean frequencies and short
 pulse periods (buzzes are made up of a series of closely spaced sound
 pulses). 2\)  variant Kent Island stimuli.wav includes the eight stimuli
 of this category used in 2016-2017. All were derived from songs recorded
 between 1994 and 2004 and have relatively low mean frequencies and long
 pulse periods. 3\)  Williamstown stimuli.wav includes the eight stimuli of
 this category used in 2016-2017. All were derived from songs recorded 500
 km from the study site, and have midrange mean frequencies and midrange
 pulse periods. 4\)  foreign Western buzzes.wav includes the eight stimuli
 of this category used in 2016-2017. All have relatively low mean
 frequencies (that do not overlap with the range of Kent Island buzzes) and
 short pulse periods. **Responses to playback stimuli** (3 csv files) There
 are three files with data describing responses to playback sessions, one
 file for each period during which playback studies were performed. The
 variable names and orders for each file vary slightly but not
 significantly (they were compiled by different authors at different
 times), and all include the following variables used in analyses: subject
 identity (ID), location, age, breeding experience, date and time of
 playback session, how long the primer was played (Primertime), stimulus
 category (StimCat), which of the eight stimulus sets was used (StimSet),
 order of presentation (trial), flights and wing flutters, songs, and
 response duration (= disengagement time; the primary response measurement
 was expressed in seconds “DisengmtTsec”). For the 2016-7 and 2022 files,
 the subject’s closest approach and average distance to the speaker were
 noted (in meters), and the subject’s songs were counted and categorized as
 either normal or soft (whisper) songs. The number of Flutter flights and
 the number of Wing flutters were summed to give the variable “Flutters”.
 The number of Whisper songs was added to Flutters to yield the aggressive
 displays variable (AggrBeh). The “Female” variable notes whether the
 female inhabiting the subject’s territory was present or absent and, if
 present, whether she responded to the playback stimulus. The “Pbstatus”
 variable is the research team's assessment of whether interference
 from other birds or humans invalidated a trial because the subject was
 responding to those other stimuli. Only trials with a status of “good”
 were used in the analyses, which is why some subjects are not listed as
 having completed all four trials. Only the disengagement time measure was
 taken for primer playback period, and so the other variables for that
 period are given as “NA” for each subject. The three files are: 1\) 
 2012playbackbuzzdata.csv summarizes responses of trials completed before
 the foreign Western songs were broadcast through speakers on the study
 site. Since the stimuli to be broadcast as part of that study had not yet
 been chosen, foreign (Western) buzz stimuli (StimType = “Stimulus D”,
 corresponding to StimCat = shortlow) were not used in the playback study
 and “NA” appears in all corresponding rows. 2\) 
 2016-2017playbackbuzzdata.csv summarizes responses to trials completed in
 2016-2017, when birds also heard foreign Western songs broadcast from
 speakers while they were on the study site. In addition to the data
 summarized above, there is a column labeled “SongType”, which describes a
 bird that had copied a foreign Western song from the broadcast speakers as
 “golden”. Ages were only available for Kent Island birds, and all subjects
 were either one year old (“FirstYear”) or two years old (“Experienced”).
 The differences between the stimulus pulse periods (ms) and frequencies
 (Hz) were determined for each subject’s buzz and the stimuli he heard.
 These distances were normalized for each measure, and then used to
 calculate the Euclidean distance between each subject’s buzz and each of
 the stimulus buzzes he heard. This value is given by the “stimdistance”
 variable, which was used to analyze the relationship between a bird’s
 aggressive response and the acoustic distance between his own buzz and the
 stimulus buzz. Because the primer had no buzz and some birds’ songs were
 not recorded, some measurements of the stimdistance variable could not be
 calculated and are given as “NA”. 2022playbackbuzzdata.csv summarizes
 responses to trials completed in 2022, when some of the older subjects had
 heard the broadcast foreign Western songs during development (denoted by
 the “TwiceSpeaker” variable), and another subset of subjects either sang a
 copied foreign Western song or heard such a song sung by a neighbor on an
 adjoining territory (denoted by the “NeighborGolden” variable). **R
 scripts** (2 files) 1\)  BuzzFamiliarityHomogeneity.R recapitulates all of
 the data analyses reported in the paper and also reproduces all but one of
 the figures from the paper. It calls on the three playback data files
 described above:             2012buzzplaybackdata.csv            
 2016-2017buzzdplaybackdata.csv             2022buzzplaybackdata.csv 2\) 
 BuzzCharacters.R reproduces Figure 2 from the paper. It calls on two files
 described above:             ForeignWtnKIBuzzes.csv            
 PBstimulisubjects_2016-7.csv ## Sharing/Access information Data can also
 be obtained from the corresponding author
 (). All data were generated from original
 research by the authors, and should be credited with a citation to the
 published paper in Animal Behaviour and to this database.