Bird migration is often used to mean oral sex by teenagers in Australia, the term comes from a Red Hot Chili Peppers song (21st century) where the two apparently unrelated terms are used together:

"Strangelation, altercation,
Oral sex and bird migration"

Andy: Planning a bit of bird migration?
Mike: As if, I only just met her!
Andy: Sure...
by Kylea July 10, 2006
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