Bird song may provide female birds with signals of male quality. To investigate this potential for sexual selection via female choice we assessed the relationships between male song variation and male mating and reproductive success of the Savannah Sparrow (Passerculus sandwichensis Gmelin, 1789) over three years (2001)(2002)(2003) in a population of Savannah Sparrows near London, Ontario, Canada. We measured song rate, and temporal and frequency attributes of song structure, as possible

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... ors of male quality, and then related these measures to attributes of male reproductive performance (males' mating and breeding success and territory size). We found significant correlations between male reproductive performance and several song features, such that the combined effects of two trill sections could potentially play an important role: males possessing such songs arrived and paired earlier, and had higher fledging success. The results suggested that the trill segments of the song may signal important aspects of male quality. Possible reasons for significant roles of such songs in open habitat birds are discussed.