Black-crowned Night Herons are common in wetlands across North America, including saltmarshes, freshwater marshes, swamps, streams, rivers, lakes, ponds, lagoons, tidal mudflats, canals, reservoirs, and wet agricultural fields. They require aquatic habitat for foraging and terrestrial vegetation for cover. They spend the winter in southern and coastal portions of their breeding range as well as across Mexico and Central America, where they use mangroves, marshes, swamps, lagoons, and flooded rice fields.Back to top
Black-crowned Night Herons are opportunists feeders that eat many kinds of terrestrial, freshwater, and marine animals. Their diet includes leeches, earthworms, insects, crayfish, clams, mussels, fish, amphibians, lizards, snakes, turtles, rodents, birds, and eggs. They also eat carrion, plant materials, and garbage from landfills. Rather than stabbing their prey, they grasp it in their bills. Black-crowned Night-Herons normally feed between evening and early morning, avoiding competition with other heron species that use the same habitat during the day. They may feed during the day in the breeding season, when they need extra energy for nesting.Back to top
The male chooses a nest site in a tree or in cattails—usually in a habitat safe from predators such as on an island, in a swamp, or over water—and then advertises for a female. Black-crowned Night Herons nest colonially, often with a dozen nests in a single tree. Colonies sometimes last for 50 years or more.
The male starts building the nest, a platform of sticks, twigs, and other woody vegetation which he collects from the ground (or breaks right off of the trees). Once he has found a mate, the male continues collecting material but passes it to the female, who works it into the nest. Some nests are sturdy, while others are flimsy. They measure 12–18 inches across and 8–12 inches high.
|Clutch Size:||3-5 eggs|
|Egg Length:||2.0-2.2 in (5-5.6 cm)|
|Egg Width:||1.4-1.5 in (3.6-3.9 cm)|
|Incubation Period:||24-26 days|
|Nestling Period:||29-34 days|
|Condition at Hatching:||Mostly helpless, covered with gray and white down, with open eyes.|
Black-crowned Night Herons nest colonially and behave socially all year long. Both males and females vigorously defend feeding and nesting territories, sometimes striking with their bills and grabbing each other’s bills or wings. This species is probably monogamous. The male advertises for a mate with displays that involve bowing and raising the long plume on his head. Both the male and the female incubate the eggs and brood the chicks, greeting each other with calls and raised feathers when switching over duties. The young leave the nest at the age of 1 month and move through the vegetation on foot, forming nocturnal flocks in feeding areas. They learn to fly when they are 6 weeks old, and then disperse widely.Back to top
Black-crowned Night Herons are fairly common, and populations were stable in most areas (but declined steeply in Oregon and Minnesota) between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 3 million and rates them 11 out of 20 on the Continental Concern Score, indicating a species of relatively low conservation concern. Threats include draining and development of wetland habitat, and reduced water quality due to contaminated runoff. They are susceptible to pollutants such as persistent organochlorine pesticides, PCBs, and heavy metals. Colonies of Black-crowned Night Herons are a good indication of overall environmental quality, because night-herons forage at the top of food chain, nest in colonies (where they are fairly easy to study), and have a wide distribution. They tolerate disturbances such as traffic, so they are especially useful for revealing environmental deterioration in urban environments.Back to top
Hothem, Roger L., Brianne E. Brussee and William E. Davis Jr. (2010). Black-crowned Night-Heron (Nycticorax nycticorax), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.
Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.
Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2019). The North American Breeding Bird Survey, Results and Analysis 1966–2019. Version 2.07.2019. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.