ROYAL OAK, Mich., June 28, 2012 – Wild black-crowned night herons have been perched in the shadows at the Detroit Zoo for about 10 years, but they are just now rising to fame as local bird watchers flock to take a gander.
Over the past decade, the night herons' original settlement at the Zoo has grown into a full-fledged rookery, hosting about 40 wild breeding pairs. With an abundance of food and safe nesting areas, it is a perfect breeding ground for the birds, according to Detroit Zoological Society Curator of Birds Tom Schneider.
"The herons just showed up one year, were successful breeding, and have been coming back ever since," said Schneider. "Local birders are embracing the opportunity to come to the Zoo to see this elusive species."
The rookery is located behind the Sweet Treats concession across from the new crocodile habitat. Zoo visitors will know they are in the right place when they hear the distinct clicking calls the birds use to communicate with each other from the treetops.
The black-crowned night heron (Nycticorax nycticorax) is normally nocturnal, making it difficult to spot outside of the breeding season. It has exceptional eyesight which helps it locate its prey. During active nesting, which spans from May through July, daytime foraging is common and the birds can easily be observed flying to and from the rookery.
The night heron's head is crowned with black feathers that extend down its back and contrast against the light-grey feathers that cover the rest of its body. Its beak is black and eyes are crimson. During breeding season, the bird's legs change in color from yellow to pink, and two to three long white plumes extend down its neck.
To attract females, the male puts on a display by snapping his beak, shaking twigs and bowing to show off his white plumes. He builds the nest until he pairs with a female, who then aids with the construction. After breeding, the female lays three to five light-green eggs that are incubated by both parents for one month before hatching. The chicks are covered in brown plumage to blend in with the environment.
The black-crowned night heron is classified as "special concern" by the Michigan Natural Features Inventory due to declining populations. The species is sensitive to wetland destruction and environmental contaminants.