What is the term used to describe oval food from birds?

The term that describes oval food from birds is "egg." Eggs are indeed a key source of nutrition in many diets around the world and are characterized by their distinctive oval shape. Bird eggs, in particular, are known for their shells, which can vary in color and texture depending on the species of bird. They are rich in protein, vitamins, and minerals, making them an important food item.

In this context, the other choices do not represent eggs or oval food from birds. Cheese is a dairy product made from the curd of milk, yogurt is a fermented dairy product, and butter is a fat derived from churning cream. None of these options relate to the product of birds specifically, thus reinforcing that "egg" is the correct and appropriate term for this question.