The danger of a bird on Earth

I am a total Earthling. By that I mean I am entirely used to this planet’s environment.

Here’s a small example:

One day I was out on my morning walk, and up ahead a wood pigeon sprang into the air and started flying toward me. With a 30-inch wingspan, it’s a fairly big bird. But I didn’t flinch. I knew that the bird, very common in that neighborhood, had no interest in messing with me. It would swerve with plenty of time.

Think about all the other potentially scary if not genuinely dangerous natural wonders we encounter on a normal day, such as a bee, dog, or cactus — to say nothing of technology.

Imagine Earthlings on a new, unexplored planet. How could they know if what looked like a bird or a mere stick of wood was really harmless? They couldn’t know. They would have to face their new world with courage.

What have you encountered so far in your day that would frighten a newcomer to Earth?