Northern Mockingbirds (Mimus polyglottos) are known to reject parasitic eggs at an intermediate rate. However, proximate mechanisms of rejection remain unexplored. Our objectives were to examine the rejection behavior of Northern Mockingbirds in northeast Louisiana, explore if nesting date or egg color of parasitic eggs influence the rate that Northern Mockingbirds reject Brown-headed Cowbird (Molothrus ater) eggs, and compare results to those of previous studies. Northern Mockingbirds rejected 68% of artificial eggs. Early nesting individuals rejected 50% of the model eggs and late nesters rejected 82%. Early nesting Northern Mockingbirds rejected 72% of light eggs compared to 27% of dark eggs. Color of the parasitic egg and date of parasitism may influence rejection rates of Northern Mockingbirds.