Sound recordings for the paper: "Variation and difference in song between Western Bonelli's Warbler and Eastern Bonelli's Warbler" by Dick Groenendijk & Teus J C Luijendijk, DB 33: 1-8, 2011.

Figure 2 Five examples of song trills of Western Bonelli's Warbler Phylloscopus bonelli illustrating amount of variation / Vijf voorbeelden van trillers van Bergfluiter Phylloscopus bonelli ter illustratie van variatie.

Bon1, bon2 & bon4 (recording of same individual / opname van zelfde individu): Tornavacas, Sierra de Gredos, Extremadura, Spain, 11 June 2002 (Arnoud B van den Berg/The Sound Approach)

bon3: Hoyos de Espinosa, Plataformes de Gredos, Castilla y Léon, Spain, 11 June 2002 (Arnoud B van den Berg/The Sound Approach)

bon5: Valencia, Spain, 15 April 2001 (Geoff Sample, as published in Sample (2003)).

Figure 3 Five examples of song trills of Eastern Bonelli's Warbler Phylloscopus orientalis illustrating amount of variation / Vijf voorbeelden van trillers van Balkanbergfluiter Phylloscopus orientalis ter illustratie van variatie.

Ori1 & ori2 (recording of same individual / opname van zelfde individu): Akseki, Turkey, 12 May 2001 (Magnus Robb/The Sound Approach)

ori3: Avas valley, Evros, East Macedonia, Greece, 27 April 2002 (Magnus Robb/The Sound Approach)

ori4: lake Megali Prespa, West Macedonia, Greece, 8 May 2002 (Magnus Robb/The Sound Approach)

ori5: Kennemerduinen, Bloemendaal, Noord-Holland, Netherlands, 15 May 1983 (Cornelis J Hazevoet, as published in Sample (2003)).