If at any time between each decennial federal census, a city annexes territory or consolidates with another city, the legislative body of the city annexing the territory or the legislative body of the consolidated city, shall reexamine the boundaries of its council districts after the first census is taken or the first current population estimates are obtained, following the annexation or consolidation.
If upon reexamination, the legislative body finds that the population of any council district has varied so that the districts no longer meet the criteria specified in Section 21601, the legislative body shall, within 60 days after the census is taken, or current population estimate received, by ordinance or resolution, adjust the boundaries of any or all of the council districts of the city so that the districts shall be as nearly equal in population as may be.