|The subject of this article has no official name.|
The name currently in use is a fan designator; see below for more information.
Pokémon nests migrate exactly once every two weeks on Thursdays at 12:00 a.m. GMT. The new species that appears is completely random and has no relationship with previous one.
Occasionally, a nest may experience a "forced migration" when an in-game event begins or ends. In some of these events, specific Pokémon species are removed from the standard spawn pool, causing some nests to shift one index up or down. The index order of the nesting species is the same as the order in which they appear in the National Pokédex. The forced migration occurs due to the nest's randomly-generated key remaining the same, but the species that key maps to potentially changing.
For instance, Pikachu is a species commonly removed from the standard spawn pool during events where it has a featured costumed form. At the start of such an event, an existing Pikachu nest would migrate into either a Squirtle or Clefairy nest, and an existing Magmar nest has a chance of either remaining the same or migrating into a Pinsir nest.