The census enumerators shall, within ten days from the date of their appointment, complete the enumeration and return their books to the city auditor. Such auditor shall then make an abstract of the enumeration and transmit it to the legislative authority at its next regular meeting after the report of the enumerators to the auditor. If the result of the census shows that the population of such city is less than five thousand, the legislative authority, by resolution, shall declare the corporate rights of the city surrendered and that each city is reduced to a village.