We compared the amount and type of acoustic competition experienced by Veeries (Catharus fuscescens) when they sang in the dawn chorus as opposed to when they sang in the dusk chorus. Veery songs tended to be masked more often at dawn than at dusk. Veery songs were masked 2.4 times per 10-song sequence at dawn and 1.2 times per 10-song sequence at dusk. A larger number of species were responsible for masking that occurred at dawn. At least 12 species masked Veery songs in our sample, and all identified species masked at dawn; only seven of the 12 also masked at dusk. These results represent the first empirical data documenting natural differences in acoustic competition at dawn and dusk. Acoustic competition may help explain why, in addition to singing at dawn, Veeries and other thrushes also have a pronounced dusk chorus.