According to

https://www.pbs.org/wgbh/evolution/educators/teachstuds/pdf/key_molecular_connection.pdf

Chickens and turkey may have evolved from a common ancestor fairly recently and have the same amino acids for cyctochrome-c. However because they cannot interbreed and produce fertile offspring, they are considered to be different species.

Why?
Because they devolop without fertilizing because they don't need it as a trait because they can survive without it. Once they needed it but now they don't.