Genesis 7:1-3

Genesis 7:1-3 mentios the animals going in to the Ark 2 by 2. God told Noah to take different amounts of different kinds of animals.

Clean beasts – 7 of every kind: Includes cattle, sheep and other animals used for sacrifices. The reason for this is clear since more than two would be needed so sacrifices could be made with out killing off the kind. They
would also be used for food after the Flood.

Unclean beasts – 2 of every kind: This would include all kinds of land animals not included in the other categories. They would be used for neither sacrifices nor food.

Fowls – 7 of every kind: This would include all winged animals not just birds but flying insects, bats and pterodactyls. Now before you jump on the “see the Bible has errors” band wagon you need to realize that the use fowls here is a translation of the Hebrew word “owph” which includes more than just birds, so the Bible is not in error here.