How do you tell the difference between a girl and a guy goose?

As it petains to Canada geese, the behavior is the easiest way to distinguish sex.

the males are fairly defiant, and act like gladiators, while the females are more chummy, and have a more warm personality.

Beyond that, the males have a call that sounds like "aHawnk" while the females go "aHinKK"..additionally when they are flying in pairs they do a duet altenating these calls that is so well synchronized it will sound like one goose doing it all. But you identify the one going 'aHinkk' and you have the female, for sure.

the only other way requires much skill, you insert a well lubricated index finger up the goose's back door, and if you feel a small lump inside, you have a male.