White-necked jacobin hummingbirds sport a colorful blue-and-white plumage as juveniles. When they grow into adulthood, males retain this dazzling pattern, while females develop a more “muted” palette of green and white—at least, most females. Curiously, about 20% of females defy the norm and retain male-like plumage into adulthood.
Click here for original story, These female hummingbirds evolved to look like males—apparently to evade aggression
Source: Phys.org