Abstract and Summary
The phenomenon of mixed singing in songbirds has recently been interpreted as one of vocal convergence facilitating interspecific competition. This paper examines the welldocumented cases of mixed singing in European songbirds with regard to the relationships between mixed singers and their models, and the frequency of occurrence of such behaviour.
Mixed singers are individual members of songbird species which in their full song extensively copy vocal patterns of an alien species and reproduce them next to their own. Models are, in most cases, taken from congeneric species, usually sibling species (Table 2). A few species, however, copy totally unrelated songbirds but some structural resemblance is often found between the vocalizations of model and imitator.
Mixed songs are usually rare, found in isolated individuals. Mixed songs can be adopted in some populations by a large proportion of the birds in situations of isolation or in small areas of overlap between largely allopatric species.
Some mixed singers of several species remain unmated or hybridize with the model species. Discounting a small number of possible exceptions, e. g. blackcap Sylvia atricapilla and garden warbler S. borin, mixed songs are best regarded as the result of misdirected song learning. There is no justification for categorizing mixed singing as an example of vocal convergence, as has been done by Dobkin (1979).