Wikia

The Parrot Cage (Hyacinth Macaw) item teaches you how to summon and dismiss a Hyacinth Macaw, a parrot Companion. It is the rarest companion in the game.

Source

Parrot Cage (Hyacinth Macaw) drops from various Bloodsail pirates in Stranglethorn Vale.

Due to a recent patch, this now drops from all mobs in the Stranglethorn Vale regions. Drop rate remains unchanged.(July 2011)

Notes

This pet has the smallest drop rate in the game, at approximately 0.0005 = 0.05%^{[citation needed]} from a very small list of mobs, and so takes an incredible amount of patience and determination in order to get one. To put the drop rate in perspective, killing 1400 of these mobs will give you a $1 - (1-.0005)^{1400} \approx 50\%$ chance to see this drop at least once. Due to the difficulty of obtaining one, and thus their rarity, they can sell for huge amounts of gold on the Auction House. Prices average from 10,000g to 20,000g on some servers, if it is seen at all.