In the 1960s, in Tully, Queensland, Australia, and in Canada, there were many reports of UFO (Unidentified Flying Object) sightings and circular formations in swamp reeds and sugar cane fields.
For example, on 8 August 1967, three circles were found in a field in Duhamel, Alberta, Canada, and the Department of National Defence sent two investigators, who concluded that it was artificially made but couldn’t make definite conclusions on who made them or how.
The most famous case is the 1966 Tully “saucer nest”, when a farmer said he witnessed a saucer-shaped craft rise 30 or 40 feet (12 m) up from a swamp and then fly away. When he went to investigate the location where he thought the saucer had landed, he found a nearly circular area 32 feet long by 25 feet wide where the grass was flattened in clockwise curves to water level within the circle, and the reeds had been uprooted from the mud.
(source : wikipedia).