DOI: 10.5061/dryad.pc866t1mr
title: Song parameters, repertoire size and song sharing within and across age classes in the saffron finch

description: Birds sing mostly to attract partners or to defend territories or
 resources. In relation to the first function, song can vary with age if
 older experienced males signal their quality through their vocal output.
 Regarding the second function, song can also vary with age if singing
 behavior helps mediate social interactions through repertoire sharing with
 neighbors. Here, we investigate whether song parameters change with age,
 and in which direction, in saffron finches Sicalis flaveola pelzelni,
 obligate secondary cavity nesters which produce elaborate melodious songs
 and show delayed plumage maturation. Cross-sectional comparisons revealed
 that second year (SY) males sing shorter syllables, and shorter and less
 versatile songs than older after second year males (ASY), as expected if
 the latter are more experienced singers. Longitudinal comparisons, which
 better depict age-related changes, showed that as birds age one year, song
 length and repertoire size do not change significantly, syllable duration
 shortens and, as expected for experienced singers, song versatility
 increases. Correlations between repertoire distance and nesting distance
 suggest that both SY and ASY males might be adjusting their repertoires to
 those of ASY neighbors; the former pattern conforms to the expectations if
 young birds try to emulate the songs of more experienced birds, while the
 latter is expected if song sharing helps de-escalating antagonistic social
 interactions amongst males. This research, which provides the first
 description of song parameters in young second year saffron finches,
 expands our knowledge of song variation across age classes in songbirds.
description: For the spectrograms of each bird in each season, we measured, by
 hand with on-screen cursor, the following acoustic parameters: maximum
 frequency (the frequency of the highest syllable in the song, kHz),
 minimum frequency (the frequency of the lowest syllable in the song, kHz),
 frequency bandwidth (difference between the maximum and the minimum
 syllable frequencies in the song, kHz), peak frequency (frequency of
 maximum power of the song, kHz), song length (duration of a song from the
 beginning of the first syllable to the end of the last syllable, s) and
 syllable duration (the mean syllable duration per song and male, s). We
 computed the syllable rate (the number of syllables produced per second,
 song and male, as in Potvin et al. 2011), the song versatility index
 (SVI)(the ratio between different syllables and the total number of
 syllables per song and male, Slater and Gil 2000) and the syllable
 repertoire size (the number of different syllables produced by a given
 male, once the cumulative number of syllables reached an asymptote with
 increasing number of songs analyzed).  Using
 cross-sectional analyses, we compared the above mentioned spectrotemporal
 variables and indexes between SY (n = 22) and ASY males (n = 17). The
 group of ASY males includes individuals that were banded as SY and are,
 therefore, of known age, as well as males that were banded as ASY, and are
 of unknown age. To avoid pseudo-replication, we used, for each male, data
 from a single breeding season. We computed the repertoire similarity
 index, i.e. a pairwise comparison of the syllable repertoire of two males,
 using the formula: 2 Ns/(R1 + R2), where Ns is the number of syllables
 shared; R1 is the repertoire size of male 1 and R2 is the repertoire size
 of male 2 (McGregor and Krebs 1982).  We conducted
 longitudinal analyses to compare the above mentioned spectrotemporal
 variables and indexes between SY males (n = 8) and the same males becoming
 ASY in the next year, and between ASY males (n = 8) of unknown age and the
 same males becoming ASY + 1 males in the second year recorded. For these
 two age classes, we also adjusted the formula of the repertoire similarity
 index described above to focus on the proportion of syllables sung by the
 same males in two seasons, such that R1 is the repertoire size of a male
 in the first season, and R2 that of the same male in the second season
 recorded (Mamede and Mota 2012). We computed repertoire similarity
 separately for both age groups because one includes males of known age (SY
 becoming ASY), and the other includes males of unknown age (ASY-ASY+1).
 All of the cross-sectional and longitudinal comparisons described above
 were made using two-sample Student’s t-tests or Wilcoxon Rank Sum tests
 when data did not distribute normally.  To evaluate the
 degree of syllable sharing amongst reproductive males at the study site,
 we tested the association between the geographic proximity of males, and
 their syllable repertoire distance (Demko et al. 2016). We used the linear
 distance between nest-boxes (m), as a measure of distance between males,
 and built a matrix of distances using geographic distance matrix generator
 (Ersts 2011), based on the geographical position of each nest-box recorded
 with a Garmin Etrex GPS (precision ± 3 m). As a measure of repertoire
 distance, we used the syllable repertoire dissimilarity, 1-RS
 (Vargas-Castro 2015, Demko et al. 2016), and built a matrix of this index
 between pairs of males. To account for the possible influence of plumage
 coloration (proxy of age) on the association between geographic distance
 and repertoire similarity, we carried out Partial Mantel test separately
 for each breeding season. The ‘color’ matrix was built by coding 0 for
 pairs of same-colored SY males, 1 for same-colored ASY males and 2 for
 pairs of dissimilar color (following   Forstmeier et al. 2006). All of
 these tests were carried using the ‘partial.mantel’ function implemented
 in the ‘vegan’ package, setting 10 000 iterations (Oksanen et al. 2017) in
 R.
description: cross-sectional_and_longitudinal_analyses.xlsx: contains
 measurements  of song parameters to perform analyses of cross-sectional
 comparisons between SY and ASY males; and longitudinal analyses of: SY
 males that became ASY males and, ASY males turning into ASY + 1
 males
 repertoire_dissimilarity_and_nest-box_distance.xlsx: contains
 data for the analyses of sharing, nest-box distance, and age between
 males.