I are moron and her Pidgey is a girl which would be find if asexual reproduction were a thing. This is what I get for giving Keiko all of two female pokes I auto-assume their all male... :/ But babies with either the Pidgeotto or Swablu at some point?

If she catches a Zubat they can make more Chatots or she can just borrow one from Yusuke's Zubat army

Shall see what I come up with.