"Evidence of birth".. It appears that somebody at the INS has suddenly developed a sense of humor! What can be further evidence of your birth than your existence! Just kidding.. I guess they are just, in their usual muddled fashion, trying to make the connection between the event of birth and who you claim to be today (I am presuming that your record of birth does not readily indicate a name). Affidavits from your parent/s affirming this should take care of this.