If I cast Selective Snare and choose a soldier token, then copy it by League Guildmage second ability, can I choose a bird token? Or I have to choose another creature which type is also soldier?

Hi,

Thanks for your question. Choices made during the announcement of the spell are copied. That includes what creature type was chosen by the original Snare. If you copy Selective Snare that had “Soldier” chosen as the creature type, the copy will have the same creature type chosen - you don't get to pick a new creature type.

706.2. When copying an object, the copy acquires the copiable values of the original object’s characteristics and, for an object on the stack, choices made when casting or activating it (mode, targets, the value of X, whether it was kicked, how it will affect multiple targets, and so on).

Thanks,
Nathan Long
Magic Rules NetRep