AAlthough it's never explained in the film, it's presumable that when Blu (still a baby) and other captured birds were smuggled from Rio and imported to the United States, the company usually responsible for sending exotic birds to local pet shops would have records of every bird species in their inventory. Tulio supposedly had done his research and called every company that distributes specified birds to local U.S. pet shops, narrowing the possible locations down to Moose Lake, Minnesota. Another possibility is that Linda posted Blu's picture on the Internet with the caption reading Blue Macaw or, while Tulio was researching blue macaws, the book store's blue macaw books came up as a suggestion so he searched its location.