My cat does this as well when a bird is close by.....they think they are going native with the lingo. Unless he is taking a course on the internet while I am out, my bird is just pretending to speak beak talk.
acorn - fruit of the oak tree: a smooth thin-walled nut in a woody cup-shaped base. acorn cup, cupule - cup-shaped structure of hardened bracts at the base of an acorn. oak tree, oak - a deciduous tree of the genus Quercus; has acorns and lobed leaves; great oaks grow from little acorns. fruit - the ripened reproductive body of a seed plant.
Not only are acorns great food for us, but for many birds and animals as well. Any deer hunter can tell you that one of the best spots to ambush a wily buck is on a trail to a big oak tree. Deer and wild turkeys harvest these nutritious acorns to fatten up for winter.