Unable to track changes on the AccountId field in Contact object

Hello,  

  I have designed an Integration queue and an event to write to the queue. A workflow writes the Contact record by tracking changes on specific fields which works fine. I noticed however, the changes on the "AccountId" field are not tracked to be pushed into the queue. To overcome this, I designed a new custom field "Parent Account Id", which populates the Account Id through a join on Contact record - this field is getting populated successfully whenever I associate an account or change an existing account.  But, the data is not getting written to the Integration event queue.