Winter breeding by Black-crowned Night Heron (Nycticorax nycticorax) in l’Albufera de Valencia, Spain, during three consecutive years is described. Winter presence in the area was recorded since 1995 and winter breeding was first confirmed in February 2001. Nests were built at roosts in wooded areas on a barrier beach, using tall pine trees (Pinus halepensis). The number of birds attending the roosts ranged 100-200 individuals, but only nine to eleven nests were built each year and only a few chicks survived to fledging. We suggest that the abundance of the introduced Red Swamp Crayfish (Procambarus clarkii) increased food availability when rice field were ploughed in early winter, and mild temperatures may have encouraged Black-crowned Night Herons to extend their presence into the winter season and to permit egg laying into the winter months. Nevertheless, the extra food supplied during rice field operations declined markedly in March and may have forced nest desertions that month.