Birth registrations for 1917 would be available from the Government. It's been awhile since I ordered a record from them but it's about $35.00. You will likely have to provide proof that your father is deceased. Birth records that are 95 years old or older are available from the Ontario Archives.
http://www.ontario.ca/en/services_for_residents/121591The alternative is to order a copy of his death registration. That document should include his DOB.
I can't think of any other way to get his DOB without ordering the certificate.