After arriving in the eighth area 'Bird Bay' a new Bankimal will appear, this will be the Pteranodon. After dislodging the trash that it swallowed you are tasked with feeding the the Pteranodon as it flies around.
Clean up the dirt mound and then deploy the Build Bot with
to create the seed plot. Buy a Fishgrass seed from the store, plant and water it. Once it is fully grown it will produce Fishberries.
Now keep an eye on the Pteranodon, eventually it will fly over you, all you need to do is aim and launch the Fishberries at it.