Is Spizella taverneri a species or a subspecies?

Based on distributional, ecologic, morphologic, and vocal data, Klicka et a l. (1999) argued in favor of species status for the form taverneri, long re garded as a subspecies of the Brewer's Sparrow (Spizella breweri). For seve ral reasons we disagree with their conclusion: lack of evidence for the rep roductive isolation of taverneri from breweri, loss of information on the c lose relationship and allopatric distribution of the two taxa that would ac company their elevation to species, and violation of the principle of taxon omic balance. Until the demonstration of vocal or display differences relev ant to pair formation and maintenance, taverneri and breweri are best regar ded as reproductively compatible subspecies.