Laying time of the bronzed cowbird

We report the first observations of egg laying by the parasitic Bronzed Cow bird (Molothrus aeneus). Three direct observations and two estimates of lay ing times were made at two Northern Cardinal (Cardinalis cardinalis) nests. Bronzed Cowbirds laid at 18.2 min +/- 1.7 (SE) before sunrise (range 14-24 min). Laying lasted 5-10 seconds. Although the parasitic Brown-headed Cowb ird (M. ater) and sometimes Shiny Cowbirds (M. bonariensis) also lay before sunrise, direct observations of laying by other cowbirds are required befo re it can be concluded that pre-sunrise laying is an adaptation for brood p arasitism.