[MENTION=6698275]Dozen[/MENTION] Consider those artifacts and phylacteries being held on by the individual adventurer, rather than the plot specific NPC.
Adventurers face danger many times throughout the day, where plot specific NPCs only face danger once (when they're designed to fight the PC).
Artifacts and phylacteries (and other valuable items) are only obtained upon killing their guardian - something easily fabricated in a dungeon sense. A Lich doesn't want to have his phylactery on site when he dies, he wants it as far away (and in as safe a place) as possible, because if he is dead; he is obviously facing something capable of destroying his phylactery.
The hawk can be taken out by a stray arrow.
Artifacts and phylacteries and the like generally cannot be.
Adventurers target powerful items and foes to hunt, prepare heroic quests for, and the like.
Hawks are neither. How many "we prepared and traveled for weeks to get the wizard's abode, disabled his murderous traps, conquered his golems and mephits, risked our lives and the lives of our friends so that we could murder the wizard's bird" stories have you ever heard?
Let it have a small, protected forest that it can happily fly and hunt in, perhaps a section of a local regent's personal woods, and call it a day.