On the morning of May 31, a rare Anna’s hummingbird turned up at the UC Santa Cruz Arboretum. Curator Melinda Kralj first spied the white “leucistic” bird hovering around the nectar-filled flowers of a Grevillea ‘Superb’, a shrub in the arboretum’s Australian rock garden. With a watering hose in one hand and her iPhone in the other, Kralj snapped a fuzzy shot of the hummer and began to share her find. Hundreds of visitors have since turned up to catch a glimpse of the brilliant white bird.
Leucism is a genetic mutation that causes hair, fur, feathers, and skin to be mostly colorless due to a reduction in melanin pigments, which in hummingbirds normally create black, gray, brown, and reddish-brown coloration in their feathers. The mutation differs from albinism—the inability to produce melanin at all. The telltale difference between the two is the leucistic animal’s normally colored eyes and, in this case, beak and feet too.
“It’s so striking,” says Todd Newberry, a birder and evolutionary biologist who volunteers at the arboretum. The adult bird’s repeated swooping dives suggest it’s likely male, but there’s little way to know where the bird came from or how long it will stay, although Anna’s are year-round residents in our region. Leucistic creatures are easy to spot and thus easy prey. Newberry is surprised the bird is still here, given a Cooper’s hawk nest with three chicks sits close to the hummer’s favorite plants. But for now, he says, “It’s a bird you go back to see again and again. It’s ghostly.”