What material is periodically regurgitated by Eared Grebes, similar to owls?

Answer

A tight mass of indigestible matter known as a pellet

Accumulated, undigested material—including feathers, fish bones, and shell fragments—is compacted into a tight mass called a pellet, which the grebes periodically regurgitate to purge their systems.

What material is periodically regurgitated by Eared Grebes, similar to owls?
fooddietbirdanimalGrebe