Why This Bird Cleaned Hippo's Teeth?

The hippo was sunbathing in the muddy pond. He saw a bird, and the bird started talking to the hippo.

“Hey, I am concerned about the health of your teeth,” the bird said.

“I know that. My tooth is aching. What can you do for me?” asked the hippo.

“I can clean your teeth. But what I will get in return,” the bird asked.

“Oh, good you have asked. If you clean my teeth, you will get plenty of things to eat from my mouth,” the hippo said.

The bird started cleaning the hippos’ teeth. She got a lot of eatable, and the hippo’s teeth were shining in the sunlight.