A Horned Screamer (Anhima cornuta) population was studied to examine its conservation status and habitat deterioration in the El Canclon Lagoon wetland (Manglares Churute Ecologic Reserve) at coastal Ecuador from February 2001 to January 2002. Weekly censuses were conducted along 100m transects around the lagoon perimeter in five survey areas, showing different degree of perturbation, during the dry and wet seasons. At least 68 screamers were observed in the lagoon. The abundance of screamers was lower (six-ten individuals) in more disturbed areas containing farms, agriculture fields and cattle ranching. Abundance was inversely associated with the presence of cattle and was not seasonally dependent during the dry and wet seasons. Screamers were significantly associated with vegetation coverage. Because the Horned Screamer strongly relies on the wetland vegetation, cattle overgrazing jeopardizes its habitat and survival in this Ramsar wetland. Best management practices and the establishment of buffer zones (i.e. 100m) are needed to mitigate the agriculture expansion and cattle ranching around the El Canclon lagoon in order to protect this threatened Anseriformes species in Ecuador.