American Coots (Fulica americana) are known for laying eggs in the nests of conspecifics, but there is little evidence that they regularly parasitize the nests of other species. I found 13 Least Bittern (Ixobrychus exilis) nests, 2 of which were parasitized by coots. These are the first records of coots parasitizing Least Bitterns, and the first records of any form of brood parasitism on Least Bitterns. Nests of Least Bitterns also were parasitized experimentally with a variety of nonmimetic eggs and 27% were rejected (n = 11 nests). This indicates that Least Bitterns may possess some egg recognition abilities.