Electronic Supplementary Material (ESM), Online (See Supplementary Material 1 for TOC)
1
Electronic Supplementary Material (ESM), Online (see Supplementary material 1 for TOC)
Supplementary material 1: Table of Contents - ESM
Supplementary material 2:Audio file of Melody 1(S1)sung by Bullfinch 1, depicted as spectrograms and in musical notation in Fig.1.
Supplementary material 3:Film and sound track (S2) (from Haanstra 1972) documenting the training methods of JN, who practised alternate singing of Melody 1 with Bullfinch 3.
Supplementary material 4:Tabular documentation (S3)- -based on a continuing recording—of the reciprocal song modules whistled by JN (framed in red) and sung by Bullfinch 5 (framed in green), while J.N trained the bird to sing Melody 3. Modules with numbered notes denote false continuations of Bullfinch 5.
Supplementary material 5:Differences in the tonal qualities (timbre) of corresponding notes (note 30 of Melody 2) of the human tutor Karl Möller, who raised and tutored Bullfinch 4, of JN, and of this bird. The comparison of the identical note of melody 2 at position 30 (eʹʹʹ in the musical notation of S5a and depicted as the entire sequence of 45 notes as spectrograms on S5d), shows that the overtones are far less pronounced in the notes whistled by both humans than in those sung by the bullfinch.
The differences in the dynamics (loudness) within note 30 are depicted in S4aas oscillograms (above) and as spectrograms (below): loudness decreases continuously for the bullfinch compared to fluctuating dynamics in the humans: These irregularities in vibration of human lips are caused by the airflow while whistling.
The pitch of a note is determined by the frequency of the fundamental. We measured the position of the fundamental and the differences in the relative power of the overtones of the notes in power spectra (Supplementary material 6 (S4b), above: Bullfinch 4, below: human tutor ). From the fundamental of 1329 Hz, one directly derives its characterization as close to eʹʹʹ in musical notation, which lies around 1318 Hz in concert pitch. Differences in tonal qualities of notes between the bullfinches and the humans result from much more pronounced harmonic contents (overtones) of the bullfinch’s’ notes.
Supplementary material 7:How Bullfinch 4 retrieves the learned human Melody 2 “Im tiefen Böhmerwald”from memory, determined by an analysis of its variability and errors when singing alone. Melody 2, in the notations of music(S5a).
Supplementary material 8: Melody 2, sung correctly and also with deviating note sequences (errors) S5b-S5h.Note particularly the grouping of sequence into smaller sequences—modules—separated via pauses, by simultaneously listening to the songs and by analysing the positions of pauses within its visualized temporal organization in spectrograms.
Audio file of Melody 2, whistled by tutor Möller, who raised and tutored Bullfinch 4 (S5b).
Supplementary material 9:Audio file of Melody 2, sung by Bullfinch 4 according to the whistled human model but ending with a supplementary note, a bullfinch’s distance call (S5c).
Supplementary material 10:Spectrogram of Melody 2 (S5d), sung by Bullfinch 4 correctly documented as audio file (S5c). Note particularly the differences in the durations of pauses between consecutive modules—the very prolonged ones, between modules 2 and 3 (between notes 12 and 13) and between modules 5 and 6 (between notes 35 and 36), and the much shorter ones between the others.
Supplementarymaterial 11:Audio file of Melody 2, sung by Bullfinch 4 with deviations in the note sequence (S5e), schematically documented as a note sequence on S5f and in the spectrogram on S5g.
Supplementarymaterial 12:Schematic documentation of the errors of bird 4 (S5f) singing Melody 2 (notes missing at the borders between modules and repetitions of modules) acoustically documented in S5e.
Note particularly that the bird continues the sequence accurately although it did not sing notes 6 and 42 (an indication of a hierarchical structure of the learned note sequence).
Supplementarymaterial13:Module repetitions and omission of notes within the terminal modules (notes 36-45) of bird 4 singing Melody 2 documented by spectrograms (S5g).
First line: According to the whistled model of the tutor. Note the correct length of the pause between note 41 and 42.
Line 2-5: Repetitions of module 6. Instead of continuing after note 41 with note 42’, the bird repeated the preceding module by restarting at note 36, the first note of module 5. Note, the lengthened pauses before repeating the module it has just sung also, at line 5, the correct continuation of the melody after note 41 with the notes 43 to 45 although the bird omitted note 42.
Supplementarymaterial14:Continuing the sequence correctly in spite of having omitted a note (S5h).
Top: Accurate note sequence (short pause between module 1 and 2 and between positions 6 and 7).
Second and third line: Note sequences in which note 6 was missed, but the bird nevertheless continued accurately. Note the bird’s elongated pauses instead of singing note 6 before starting again with note 7.
Supplementarymaterial 15: Spectrograms and audio files of alternate singing with flexible entries for Melody 2 of Bullfinch 4
Spectrograms of entering after position 24 (S6a). Numbers of notes framed in red show modules whistled by JN; those framed in blue are sung by Bullfinch 4.
Top: entering late (0,5s) at note 25’. Centre: entering with parallel singing at note 24’, bottom: entering too early (0,2s) with note 25’.
Supplementary material 16-18:Sound tracks (S6b – S6d) of the recordings, depicted on S6a
Top centre bottom
Supplementary material 19: Schematic documentation of the variable points of entry (S7) and singing modules, based on a continuing recording, within the alternate singing of Melody 2 by Bullfinch 4 (blue) and JN (red). Modules with numbered notes denote incorrect entries and incorrect continuations.
Supplementary material20: Melody 3, depicted in musical notation (S8).