Tricoloured heron  (Egretta tricolor)

The tricoloured heron is classified as Least Concern (LC) on the IUCN Red List (1).

A colourful water bird of the Americas, the aptly named tricoloured heron (Egretta tricolor) has slate-grey upperparts that contrast with bright white underparts and reddish stripes on the neck. There are long purplish-maroon feathers on the back, the long, thin bill is orange to brown-yellow and the elongated legs are yellow or orange with thin, un-webbed toes. The tricoloured heron is even more vibrantly coloured during the breeding season, with the bill becoming bright blue with a black tip, the neck feathers bluish-purple, and the legs deep pink. A crest of white plumes also develops on the head, and the neck and shoulder feathers turn violet (2) (3).

The male and female tricoloured heron are similar in appearance, although the male is typically larger, but the juvenile has brown upperparts with white on the chin, the front of the neck and the belly, a chestnut-grey streaked breast, a black-tipped yellow bill and green-yellow legs (3).

The tricoloured heron occurs in eastern and southern USA, Central America, the Caribbean and northern South America (3).

Primarily a coastal bird, the tricoloured heron is most commonly found in saltwater wetlands, such as shallow salt marshes, coastal lagoons, mudflats, tidal creeks and mangrove swamps (2) (3).

Foraging in open or semi-open wetland areas of brackish or salt water, the tricoloured heron tends to hunt in deeper water than other heron species, feeding mainly on small fish but also eating insects, crustaceans and frogs. It uses a variety of hunting strategies, including standing still, patiently waiting for prey to come within striking distance, and a running pursuit with the head held low to the water and the bill stabbed at prey with an almost horizontal action (2) (3) (4).

From February until late May, the male tricoloured heron builds a nest in either a colony of mixed species or with other individuals of the same species. A loose platform of large twigs up to three and a half metres above the ground or water is constructed in a well-shaded tree or shrub (3) (5). Once a monogamous pairing is formed, the female completes the nest with twigs collected by the male. Three to five eggs are laid, with clutches often larger in freshwater colonies. Both the male and female tricoloured heron incubate the eggs over approximately 22 days. The hatchlings can perch at the side of the nest by 17 days, leaving the nest at 21 days and departing the colony at around 51 to 56 days (3).

With the legs extended and the head drawn in to the shoulders, the tricoloured heron flies using strong, steady wing beats. It usually travels alone but may occasionally fly in flocks. It rapidly descends from flight by partly folding its wings and rocking from side to side, in a manner similar to a falling leaf. With the exception of South American populations, most tricoloured herons migrate (3), with birds from southern and eastern USA migrating southwards to Central America and the Caribbean (2).

While the tricoloured heron has a large, stable global population and is not currently at risk of extinction, it is threatened in parts of its range by disturbance, habitat loss and pollution (6).

It is particularly vulnerable to human interference while nesting, as it can cause breeding birds to abandon their nests and eggs, leaving the brood defenceless against predators and exposure. This threat was particularly significant during the late 1800s, when hunters disturbed tricoloured heron nests whilst targeting other bird species in mixed colonies for the plume trade. Breeding success has also been lowered by pollution, as toxins, which are ingested through the congestion of contaminated prey, can reduce eggshell thickness (3).

The tricoloured heron may occasionally be hunted for food, and its eggs may be harvested. Culls are also occasionally permitted around aquaculture farms to limit the impacts of this species’ predation upon farmed crustacean stocks. In the Florida Everglades, the tricoloured heron population has been in decline as a result of habitat degradation and associated decreased food availability (3).

The tricoloured heron has benefited from the protection of islands and coastal areas in the USA as part of the National Wildlife Refuge system. It is also profiting from the construction and maintenance of artificial islands on the Atlantic coast, which protects nesting birds from terrestrial mammalian predators that cannot access the islands (3).

Additional conservation recommendations for the tricoloured heron include setting designated pathways at a certain distance from nesting sites to prevent disturbance. Suitable habitat in the Florida parts of its range should also be identified and protected (3).

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

More information on the tricoloured heron and other bird species:

• BirdLife International:
  http://www.birdlife.org/

 More information on heron conservation:

• IUCN/SSC Heron Specialist Group:
  http://www.wetlands.org/Aboutus/Specialistgroups/HeronSpecialistGroup/tabid/193/Default.aspx