Negro, a scientist at the Estación Biológica de Doñana at Pabellón del Perú, Spain, and his colleagues began by documenting all bird species that are known to blush. Birds with a penchant for blushing include ostriches (
Struthio camelus), the crested caracara (
Polyborus plancus), the hooded vulture (
Necrosyrtes monachus), and the pied-billed grebe (
Podilymbus podiceps), as well as pelicans, turkeys, and other birds.
The researchers determined that most blushers are dark-colored, large species that tend to live in hot climates.
The scientists then analyzed in detail the facial skin of crested caracaras and hooded vultures. Samples were taken from both feathered and bare skinned portions of the birds' faces.
