If you find your person in someone else's tree, rarely they have posted the birth certificate. But, if they have the full DOB, they HAD to get the information from somewhere. Contact them via the Ancestry message system and ask the source of their information. They may be a closer relative to the person.
--Based on your other postings, "IF" this posting is based on another of your postings looking for James Loring McCormick… This person is found in a posted family tree owned by a Marlene Steiner. He was born May 31, 1920 in Boise, ID. His obit is posted. Marlene "might" have further info on birth. I didn't look over the rest of your obit inquiries, but obit attached.
Birth certificates are legally confidential in Idaho for 100 years. Death, stillbirth, marriage, and divorce certificates are legally confidential in Idaho for 50 years.http://healthandwelfare.idaho.gov/Families/BirthDeathMarriag...
So, you will not find a database, nor would you be able to order the birth certificate unless you meet family qualifications. I do have access to some period newspapers, but didn't know who you were researching.
Many other States have serious restrictions on putting birth and death records online. Some have formerly requested the Social Security Administration to stop putting this data in the Death Master File (the basis for the sold data in the SSDI). http://www.ntis.gov/pdf/import-change-dmf.pdf
Posting the name of the person being sought would allow volunteers to do research. Finding the persons death data might give enough information as to DOB. You might even find someone related. I very frequently find individual Census to have errors, but a concensus review helps to identify a pattern of truth. One might say born in Idaho, when actually born in Illinois.