Pokemon Go nests are specific coordinates where a Pokemon is known to spawn on a frequent, regular basis. These hotspots are miniature meccas for Pokemon Go players, especially when a nest spawns Pokemon that can evolve into an even more powerful form. Last month, ComicBook.com reported that the nests had suddenly "migrated", causing different Pokemon to appear than before. Niantic declined to give information on the spawn shift, but many wondered if the change would occur on a regular basis.

Last night, Pokemon Go's nests suddenly shifted again, with new Pokemon spawning from the Pokemon Go hotspots. The shift seemed to coincide with the release of Pokemon Go's newest update, which also began its rollout on Monday. Like the last nest migration, there appears to be a pattern to the shift. Nests have shifted one unevolved Pokemon "forward" in the Pokedex. For instance, a Bulbasaur nest now spawns Charmanders and a Charmander nest now spawns Squirtles. Some nests are also spawning two different types of Pokemon instead of one.

Based on the previous two migrations, it seems that the migrations occur every three weeks. The purpose of the migrations are still unclear, but it's possible that Niantic is just trying to mix things up for its most dedicated players.

Here are all the nest migrations we know about so far, courtesy of /r/TheSilphRoad. The old Pokemon are on the left and the new Pokemon are on the right.

Bulbasaur -> Bulbasaur/Charmander

Charmander -> Charmander/Squirtle

Squirtle -> Squirtle/Charmander

Ekans -> Pikachu

Pikachu -> Sandshrew

Sandshrew -> Nidoran (female)

Nidoran (female)-> Nidoran (male)

Nidoran (male) -> Clefairy

Clefairy -> Vulpix/Nidoran (male)

Vulpix -> Jigglypuff

Jigglypuff -> Vulpix

Oddish -> Paras

Venonat -> Diglett

Diglett -> Meowth

Meowth -> Psyduck

Psyduck -> Staryu/Mankey

Mankey -> Growlithe

Growlithe -> Poliwag

Poliwag -> Abra

Abra -> Machop

Machop -> Bellsprout

Bellsprout -> Tentacool

Tentacool -> Geodude

Geodude -> Ponyta

Ponyta -> Slowpoke/Magnemite

Slowpoke -> Magnemite/Doduo

Magnemite -> Seel/Doduo

Doduo -> Seel/Shellder

Seel -> Shellder/Gastly

Shellder -> Gastly/Onix

Gastly -> Drowzee/Onix

Onix -> Drowzee/Krabby

Drowzee -> Krabby/Voltorb

Krabby Exeggcute/Voltorb

Voltorb -> Cubone/Exeggcute

Exeggcute -> Cubone/Rhyhorn

Cubone -> Rhyhorn/Horsea

Rhyhorn -> Horsea/Goldeen

Tangela -> Cubone

Horsea -> Staryu

Goldeen -> Scyther/Staryu

Staryu -> Jynx

Scyther -> Electabuzz/Jynx

Jynx -> Magmar/Electabuzz

Electabuzz -> Magmar/Pinsir

Magmar -> Magikarp

Pinsir ->Eevee/Magikarp

Magikarp -> Omanyte/Eevee

Eevee -> Kabuto/Omanyte