This seems to have been a provision made for poorer Israelites, that such as had not ability to offer a beast of great expense, might bring a less. Luke 2:24.
Related Commentaries of Leviticus 1:10
Leviticus 1:10
10 And if his offering be of the flocks, namely, of the sheep, or of the goats, for a burnt sacrifice; he shall bring it a male without blemish.