The animal on the cover of Building Web Reputation Systems is a Pionus parrot. The Pionus genus includes eight different species. These medium-size birds are native to Mexico, Central America, and South America, and are characterized by a stocky body, a naked eye ring, and a prominent beak. In addition, they have short, square tails with red coverts (undersides), and as such, have also been known as red-vented parrots.One unique characteristic of the Pionus parrot is its stress response. When threatened or intimidated, the birds exhibit one of three different behaviors. The most severe is thrashing; if something frightens them, such as their cage being struck or jarred while they are asleep, the parrot will thrash around until it is calmed. The second response is total stillness; at bird shows, a Pionus may be observed sitting completely motionless while other species scream or demonstrate more common stress signals. Finally, when frightened or excited, the Pionus emits a very distinct wheezing or snorting sound, almost as though it is having an asthma attack.