Savalli, U.M. 1995. The evolution of tail-length in widowbirds (Ploceidae): tests of
alternatives to sexual selection. Ibis 137: 389-395.
The long tails of male widowbirds (Euplectes, Ploceidae) have been used to test sexual
selection theory, but alternatives to sexual selection have not been investigated. This study
tests three alternative hypotheses for the evolution of tail-length in widowbirds: aposematism;
the unprofitable prey hypothesis; and species recognition. Using museum specimens,
geographic patterns of tail-length were examined for evidence of character convergence (as
predicted by the aposematism and unprofitable prey hypotheses) or character divergence (as
predicted by the species recognition hypothesis) in areas where two pairs of species were
sympatric. There was no consistent trend: one species showed evidence of character
convergence, and the other some evidence of divergence. Experimental manipulation of taillength in the Yellow-shouldered Widowbird, E. macrourus , also failed to support the species
recognition hypothesis: there was no preference for males with species-typical tail-lengths,
but instead a slight, non-significant trend to favour short-tailed males. There was also no
evidence that mistaken identity led to territory loss following these experimental
manipulations. Tail-length of six Euplectes species did not correlate with unpalatability
scores, as predicted by the aposematism hypothesis. These hypotheses do not appear to
explain the evolution of long tails in widowbirds, suggesting that sexual selection is the sole
factor favouring long tails. Interspecific variation in tail-length remains unexplained.