The phrase “The eagle has left the nest” could apply to either a biologist describing an actual event, or a cliché coded-statement used commonly in action movies to describe something or someone leaving a place.
The Author noticed this slightly ambiguous statement and decided to use his “My Hobby” web comic template to fabricate a joke about it.
Note: People with some forms of Autism, including Asperger Syndrome, have dramatically heightened recall for long-term memory. This ability is believed to be caused by an increase of “white matter” in the brain. It can also increase autoassociative memory activity, causing related memories to be recalled upon hearing or seeing associated words, phrases or objects.