THE IMITATIVE RANGE OF THE SONG OF THE MARSH WARBLERACROCEPHALUS PALUSTRIS, WITH SPECIAL REFERENCE TO IMITATIONS OF AFRICAN BIRDS

Abstract

SUMMARY This paper presents the first extensive evidence of vocal imitations of African birds by a Palaearctic migrant, the Marsh Warbler Acrocephalus palustris. Nearly 30 individual tape recorded repertoires have been analysed, most of them from Belgium; imitations of each identified species were compared to models by spectrographic analysis. A list of 113 African species (33 non‐passerines, 80 passerines) was thus established (Appendix), which, added to the list of 99 European species, gives a total imitative range of 212 species. The low‐pitched voices of many non‐passerines exclude them from imitation. Vocal imitations of some rather local species in East Africa provide information on the localization of the autumn and winter quarters of A. palustris. In particular, the frequency of imitations of such species as Vinaceous Dove Streptopelia vinacea, Boran Cisticola Cisticola bodessa and Red‐pate Cisticola C. ruficeps lends support to the idea of the existence of autumn quarters in northeastern Africa. Individual repertoires contain an average of 76.2 different imitated species (extremes 63–84), the number of African species (average 45.0) exceeding that of European species (average 31.2). About a fifth of the complete song remains unidentified and probably corresponds to imitations of African birds whose voices have not yet been recorded. The most recurrent imitations are those of noticeably noisy species, widespread in Africa. A. palustris appears not to be selective in its repertoire. Imitations of different species can, to some extent, be combined and alternated into original motifs. Circumstantial evidence indicates that the young A. palustris are still learning song motifs when on their way to their winter quarters and probably stop learning soon after their arrival there, most of them in January, at the age of 6–7 months. There is a temporal separation between the sensitive phase and the motor phase of song learning. No conclusion as to the possible functions of the imitative element of the song can be drawn at present.

Avian vocal mimicry: a unified conceptual framework

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