To make Mawhawk appears you have desecrate a Shrine 500 times, to do that you have to use a Silencer Extretion on a Shrine.
After u use the Silencer Extretion the following message with appears.
Keep in mind that when you dessecrate the altar a Guzzlemaw will spawn near the shrine when you desecrate it.
After do that you have to wait until next Server Save to Mawhawk appears in his places Here.
There isn't a certain time of the spawn the Mawhawk can take 5 mins to respawn to 2h, it is completaly random.
And the respawn will be open from the Server Save until the next Server Save.
Sources: UPDATE 10.3, Roshamuul Quest, Mawhawk,