Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

The comic presents three panels contrasting how different people react to seeing a bird's nest. "What normal people do" shows a person simply exclaiming, "Hey look! A bird's nest!" "What normal people think biologists do" shows a scholarly-looking man identifying the nest as a fine example of the nest-building technique of T. migratorius, the American Robin. "What biologists actually do" shows a biologist looking at the bird on its nest and musing, "I wonder how she'd behave if I replaced her eggs with rocks, then simulated a bear attack."

The joke contrasts public perception of scientists as dignified observers of nature with the reality that experimental biology often involves devising bizarre, invasive experiments to test animal behavior. The biologist is not content to simply observe or classify -- she wants to manipulate variables and stress-test the bird to see what happens.

The Humor

The humor lies in the escalation across three panels. The normal person is charmed by nature. The imagined biologist is a sophisticated but passive observer. The actual biologist is essentially plotting a cruel prank on a bird, framed in the language of experimental design. The specific details -- replacing eggs with rocks AND simulating a bear attack -- make it funnier because it is not just one weird experiment but a combination of two manipulations, suggesting the biologist is enthusiastically piling on variables. The biologist's calm, contemplative expression while planning this makes it even funnier. The joke resonates with anyone familiar with actual animal behavior studies, which often involve exactly this kind of creative torment.

References

T. migratorius is the scientific name for the American Robin (Turdus migratorius), a common North American songbird. The comic's depiction of the biologist's experimental mindset is a fairly accurate (if exaggerated) portrayal of behavioral ecology research, where scientists routinely manipulate nests, swap eggs, introduce predator models, and perform other interventions to study animal responses.