 Recorded dietary items include sago shoots and insects , and it also swallows small stones to help break up its food . It is apparently monogamous , but little else is known of its courtship behaviour . The only known nest was a shallow bowl in the top of a rotting tree stump that was lined with wood chips and dry leaves . The two young chicks were entirely covered in black down typical of precocial newly hatched rails . The estimated population of 3 @,@ 500 – 15 @,@ 000 birds and the restricted range mean that the invisible rail is classified as vulnerable by the International Union for Conservation of Nature ( IUCN ) . Habitat loss has occurred through the harvesting of sago and conversion of the wetlands to rice cultivation , and the rail is eaten by local people . The described nest was in an area frequented by local villagers , so the rail may be more adaptable to habitat changes than had been thought . 
