Heron, Boat-billed



Cochlearius cochlearius ridgwayi


Size is approximately 20 inches (50 cm) long and weight is approximately 21oz (600g). Sexes are similar.  Short, very broad flat beak is as wide as the broad head.  Wingspan is approximately 2.5 feet. Its color is silvery-grey with black on the crown and upper back, and a short crest of black feathers. The forehead, throat, and breast are white, and the sides of the body are black. The large eye has a dark brown iris with a greenish-yellow eyelid.  Voice is likened to a frog-like croaking, or at other times a squawk or a bark.  It also rattles or claps its bill.

Family

Ardeidae

Order

Ciconiiformes

Class

Aves

Range

Mexico south to Argentina

Habitat

Wetlands, marshy areas, mangroves and woodlands near water.

Life Expectancy

Sexual Maturity

Diet

In the wild, they eat fish, amphibians, worms and crustaceans. In the Zoo, they are fed a variety of fish, omnivore diet, bird of prey diet, and flamingo diet. The latter three are scientifically, commercially prepared diets.

Status

IUCN - Least Concern

Behaviors

A solitary species, most live in swamps with thick shrubbery or forests near freshwater lagoons and rivers. Boat-billed herons seem to be strongly nocturnal, very similar to black-crowned night herons. By day they preen and roost quietly in dense mangrove thickets near feeding areas, venturing out at dusk to forage. Its secretive behavior has made this species difficult to study in the wild. Until recently, little more was known about it other than the colors in its plumage. The boat-billed heron is one of the “night” herons; they are known for their stocky build, with relatively short, thick bills and short legs. They are particularly nocturnal feeders with large eyes, but they also feed during the day during breeding season. It is thought that the boat-billed heron catches its prey mostly by touch, rather than sight. They rely more on acoustic signals that penetrate the mangrove tangle, instead of visual signals characteristic of most heron communication. Distressed herons often rattle their bills, sounding similar to toucans and roadrunners. They hunt in the wade and stab manner of other herons, but switch to touch feeding during breeding season. Herons can be told from other long-necked birds while in flight by the fact that they always draw their necks into an “s” and hold the back of the head at the base of the neck over the shoulders. This keeps the weight of the comparatively heavy bill close to the center of gravity. They fly with endurance using slow, often-shallow wing beats. Herons do not soar. Mated pairs do a great deal of ritualized mutual preening, which serves to strengthen the pair bond. The male erects its long crest in courtship display and both clatter vigorously with their beaks. Boatbills nest alone or in small colonies that may include other species of water birds. Each pair defends a three dimensional territory around the shallow stick nest. A clutch is 3 to 4 pale greenish-blue eggs, sometimes bearing small red flecks, is laid at roughly 2-day intervals. Incubation begins with the first egg and the chicks are altricial. Both sexes share in nest building, incubating and feeding the chicks. They nest in trees, bushes or occasionally in reedbeds. Incubation period is 21-26 days. Nestling period is 6-8 weeks.

Adaptions

Herons do not have a crop, but do have a well-developed proventriculus (glandular part of the true stomach usually located between the crop and the gizzard, the grinding second part of the true stomach). Being part of the true stomach, the digestive juices would be active and anything not killed in capture would quickly die, but would not in a crop. Herons are wading-walking birds and do not run well. The first toe is elongated, for support on vegetation and mud, and all toes are quite prehensile. Small herons often hold onto vertical stalks of reeds while hunting, and all perch well on branches. Heron preen glands are vestigial, and herons do not oil their feathers. Instead, they have powder down (cockatoos and some other parrots have powder down, too). Powder down is a particular kind of feather that is never molted out, and it continuously grows. The tips gradually crumble into a powder, and this powder is spread over the feathers during preening. The feathers are effectively waterproofed, and the powder clears grease and other fish remains from the plumage. The claw of the middle toe in herons has a serrated edge that also aids in plumage care.

Special Interests

Folklore

The name “heron” is related to the Greek word “krizein,” which means, “to cry out or shriek.”

Conservation

Jacksonville Zoo History

Exhibit

Emerald Forest Aviary