Little Blue Herons are common but easily overlooked residents of marshes and estuaries in Southeast North America.
This is a fairly small heron with a slight body, slender neck, and fairly long legs. It has rounded wings, and a long, straight, spearlike bill that is thick at the base. Adult Little Blue Herons are very dark all over. At close range or in good light, they have a rich purple-maroon head and neck and dark slaty-blue body. They have yellow eyes, greenish legs, and a bill that is pale blue at the base, black at the tip. Juveniles are entirely white, except for vague dusky tips to the outer primaries. Immatures molting into adult plumage are a patchwork of white and blue. They are smaller than a Great Blue Heron and about the size of a Snowy Egret. They have a length of 22.1-29.1 inches (56-74 centimeters), a weight of 10.4-14.5 ounces (296-412 grams), and a wingspan of 39.4-41.3 inches (100-105 centimeters).
Little Blue Herons occur patchily thoughout U.S, Mexico, Central America, and the islands on the Gulf of Mexico. They are residents to medium-distance migrants, migrating south. Little Blue Herons nest and forage in many kinds of wetlands. They nest mostly in shrubs and small trees in standing water or upland sites on islands, including artificial islands created from dredged material. Rarely, they seek prey in upland pasture sites. They usually forage in water 2–6 inches deep, often gravitating toward densely vegetated foraging sites. In wintertime, Little Blue Herons make especially frequent use of mangroves, lagoons, salt ponds, mudflats, and savannas.
Little Blue Herons nest in low shrubs and small trees, in protected areas below the canopy. They may also choose flooded areas or islands as added protection against predators. Little Blue Herons and neighboring colonial birds have a pronounced impact on their nesting habitat—stunting the growth of vegetation by harvesting nest material and sometimes killing trees outright by the accumulation of guano. After pairing up, a male and female spend 3–5 days building a porous platform nest of long, mostly leafless twigs and sticks lined with greener vegetation. Usually the male finds nesting material and passes it to the female, who constructs the bulk of the nest. He occasionally assists her, or performs ritual twig-shaking displays nearby. The nest has an outside diameter of 1–1.5 feet.
Per clutch, Little Blue Herons will have three to four eggs. The eggs are pale bluish green with a length of 1.6-2.0 inches (4.1-5.1 centimeters) and a width of 1.2-1.4 inches (3.1-3.6 centimeters). Incubation period is 22-23 days and nesting period is 35-49 days. At hatching, they are covered with sparse white down with eyes partially open.
Little Blue Herons forage by wading up to their bellies in wetlands, with their necks extended stiffly forward and bills tilted down, occasionally swaying the head and neck as they size up their prey. Little Blue Herons often forage with other species, and they are gregarious breeders, nesting in multispecies colonies alongside other waterbirds. They may chase and attack other members of their own species in defense of food or nesting territory, striking and jabbing at each other with their bills.
Little Blue Herons fly with slow, steady wingbeats, usually with neck and head pulled back against the body. A courting male points his bill straight upward, suddenly extending and retracting his neck. Little Blue Herons of both male and female, when courting, may occasionally grasp, pull, and shake branches while simultaneously erecting the feathers along their head, neck, and back. Nestling Little Blue Herons, along with many other waterfowl, compete fiercely for the food their parents bring back. In lean years, the older chicks may attack and sometimes kill their younger, smaller nestmates to claim the food for themselves—a behavior known as siblicide.
Little Blue Herons are usually silent, but they can utter hoarse, harsh squawks and croaks. They also clack their bills to communicate. This can be a loud, forceful, aggressive snapping, or a gentle rattle usually given between members of a pair.
The Little Blue Herons' populations have suffered a large decline recently. Habitat loss and human-caused changes in local water dynamics pose the most serious threats to regional populations. Little Blue Herons that forage at fish hatcheries are vulnerable to illegal shooting, and the U.S. Fish and Wildlife Service and some states issue permits to legally shoot them. Like all waterbirds, Little Blue Herons are vulnerable to changes in water quality. Birds that eat prey from flooded agricultural fields and drainage ditches risk contamination by pesticides and heavy metals. Human disturbance has also been shown to harm colonial breeding bird populations, causing adults to abandon nests, eggs and chicks to die, and other impacts. Closing wading-bird colonies to human disturbance during the breeding season can help protect Little Blue Herons.
- During the feathered-hat fashion craze of the early twentieth century, Little Blue Herons’ lack of showy “aigrette plumes” saved them from overhunting that decimated other heron and egret populations.
- Little Blue Herons may gain a survival advantage by wearing white during their first year of life. Immature birds are likelier than the blue adults to be tolerated by Snowy Egrets. And in the egrets’ company, they catch more fish. Mingling in mixed-species flocks of white herons, immature Little Blue Herons probably also acquire extra protection against predators.
- Little Blue Herons in transition from the white first-year stage to blue adult plumage are often referred to as “Calico,” “Pied,” or “Piebald.”
- To distinguish the immature Little Blue Heron from its relatives, the slow, deliberate movements sets it apart from its relatives, which tend to move more quickly or erratically.
- A row of built-in “teeth” along the Little Blue Heron’s middle toe serves as a grooming comb. The bird uses it to scratch its head, neck, and throat.
- The oldest known Little Blue Heron was at least 13 years and 11 months old when it was found in Maryland in 1971. It was banded in 1957 in Virginia.
- Little Blue Herons are also called Garceta Azul (in Spanish) and Aigrette bleue (in French).