The island was established under the Pyrenees Treaty of 1659 under the joint sovereignty of Spain and France.The agreement was reached after 30 years of war. To commemorate this, a stone pillar was erected in the center of the island.
According to the treaty, the island was under the rule of the naval commanders of San Sebastian, Spain, from February 1 to July 31.It will then be part of the city of Bayonne, France, from August 1 to January 31.Every six months, at the end of the term, delegates from Spain and France meet on the island and officially hand over the documents to the next ruling country.
Pheasant is an island without permanent human habitation. It was once an important venue for royal weddings between French and Spanish rulers. As of January 2018, the island is approximately 200 m long and 40 m wide. Another feature is that it is one of the submerged islands. This rare island will not exist on earth for long.