In 1539, Charles V, co-King of Aragon, of which Sicily was a fiefdom and Malta a part, granted use of the island of Malta to the Knights.of the Order of St John along with the responsibility of garrisoning Tripoli. In exchange for this kindness, the knights offered to celebrate a daily mass for Charles. Or, in lieu of a mass, the emperor, an avid falconer, could elect to receive a prized falcon annually in tribute. He chose the falcon.
Charles V didn't "give" Malta to the knights, he let it to them, under feudal contract. This is why the text of the grant specified what should happen in case of succession of the Order's Grand Master, expressly who should assign the bishop of Malta. In this regard it specified that the Viceroy of Sicily, and not the knights, would appoint the bishop of Malta. Perhaps most telling are the conditions for returning Malta to Sicily if and when the Knights were able to reconquer Rhodes their original home, or if it decided itself to relocate elsewhere.
And so, annually, on the first of November, the Feast of All Saints, a falcon was delivered by the knights to the king's representative. So, in fact, the falcon was paid not directly to the King of Spain, but to the Viceroy of Sicily.
The position of Master Falconer was of great import to the Order and the symbol of his office was an ivory baton topped by a carved eagle's head. An example of this symbol of office is housed in the Order's museum at their headquarters at St John's Gate in London.
The Maltese Falcon, by Dashiell Hammett, has some basis in historical fact.
Hence, the tale of the Maltese Falcon.