The animal on the cover of PHP: The Good Parts is a Booted Racket-tail hummingbird (Ocreatus underwoodii). The Booted Racket-tail is a species that, as its name suggests, is noted for a pair of distinctive features: a split tail that is sometimes thought to resemble a pair of tennis rackets with elongated handles and small heads, and legs clad with downy white feathers, causing the bird to appear to be wearing boots. Female Booted Racket-tails also sport white breast plumage.
The Booted Racket-tail is a South American variety of hummingbird, and can be found along the Andean cordillera, in the rainforests of Bolivia, Ecuador, Peru, and Venezuela. Because of its fairly widespread habitat, the bird is considered relatively common in western South America. Nonetheless, Booted Racket-tails are a popular subject for birdwatchers and photographers visiting the region, likely due to the species’ distinctive appearance.
In 2004, researchers from the University of California, Berkeley, and the California Institute of Technology included Booted Racket-tails in a study of Peruvian hummingbirds intended to discover why the species remained mostly at lower altitudes, as opposed to venturing up higher where there is less competition for food. Not surprisingly, the researchers noted that at higher altitudes, where the air is thinner, the hummingbirds demonstrated a loss of power and maneuverability, hampering their ability to thrive.
An image of Booted Racket-tails also appeared on a 1996 ...