 The Zapata rail appears to have been easily found in the Santo Tomás area until 1931 , but there were no further records until the 1970s when birds were found 65 km ( 40 mi ) away at Laguna del Tesoro . The few records in subsequent years suggest that numbers remain low , although after no official sightings for two decades , a 1998 survey found the birds at two new locations in the Zapata Swamp . Ten rails were detected at Peralta , and seven at Hato de Jicarita . On the basis of this sample it was estimated that 70 – 90 rails were present in the 230 hectares ( 570 acres ) between the two sites . 
