I was having a really fun time playing and I was really excited when I heard legendaries were coming, the only legendary I really wanted was Articuno, I had no idea about the two week time limit. In fact, I only found out about it after the last day I could have possibly caught an Articuno. Its unfair that you reward the team that won the competition by giving them two weeks to catch their legendary bird, while giving the other birds an entire month, and then deleting them from the game forever! If you bring them back, Ill change my rating.
It would be nice if you bring them back after Zapdos is release just with a lower capture rate (maybe 1-0.5%) than the other legendaries, I would even be fine if you did these challenges every year or maybe even twice a year, but having the wining teams bird appear for two weeks and then having it never show up again, not cool, Niantic!
I saw lots of Articuno raids, but every single time, I was either busy or in a car. You need to think about what people are doing even in summer, its not like everyone is magically free from everything for a while.
OsoTanuki about Pokémon GO, v1.39.0