Dropping out of the opalescent sky with its neck neatly tucked back, the heron floated into view. Swinging its long legs forward at the last second, the graceful bird landed at the edge of an open pool of water. The blue-gray body stood out against the tawny marsh grasses.

Seeing herons at the Chincoteague National Wildlife Refuge in Virginia is a common occurrence, but this bird was a bit different than most. A sinuous white line ran down the thin throat, eventually spreading into an all-white belly.

It was late March last year, and it seemed too early in the season for this southern visitor. But no other dark heron has that throat stripe and white belly. I saw while the bird was landing, that its underwing linings were white, too. This was a tricolored heron (Egretta tricolor).

The bird was a beauty, in full breeding plumage. Standing about 2 feet tall, the tricolor has a 3-foot wingspan. The fleshy area in front of the eyes and the base of the bill were a brilliant turquoise. A few white plumes extended from the back of the head. Wispy chestnut feathers edged the throat line. Mauve patches on the shoulders and back blended seamlessly into the blue-gray body feathers. Its legs were pink, and its eyes red. The sexes look alike.This adult is just short of its prime breeding colors, lacking only its turquoise eye patch and pink legs. (Ryan Hagerty, courtesy of the US. Fish and Wildlife Service)

Tricolors are permanent residents of the Gulf Coast, parts of the Caribbean and Central America, and the coastal marshes of northern South America. Every spring, some fraction of the birds from these regions migrate north to breed.

From April to August, a modest number of these herons breed and raise their young around the Chesapeake, Delaware and inland bays. By September, their numbers will expand as post-breeding birds from farther south come our way to explore and feed on abundant fish. Most will depart by December.

Tricolors are colonial nesters. They usually roost and nest with other species, with the tricolors tending to occupy the periphery of colonies. When they forage, they exhibit similar behavior, hunting alone or on the edge of mixed flocks of wading birds.

Nests are constructed by both parents. The male starts by placing some sticks in a low tree or shrub. Later, he brings sticks to the female for final placement. Both parents incubate the three to-five eggs in the single annual clutch. It takes three weeks for the eggs to hatch and nearly as long again before the chicks fledge.

Juvenile tricolors have a wood brown neck and considerable brown in the body feathers.

After breeding, adults will molt into their “basic” plumage, losing many of their flashy colors. Gone is the turquoise patch, replaced by yellow. The eyes and legs revert to brown. The mauve highlights in the wings and back are replaced by a more muted lavender. Fortunately, the diagnostic white throat stripe and white belly are retained in all plumages, including juvenile.

Tiny fish make up 90 percent of the tricolor’s diet. Occasionally, they eat frogs and insects such as grasshoppers.

Tricolors only feed during daylight. They often wade into deeper waters than their close relatives: the snowy, little blue, and reddish egrets. With its belly nearly touching water, the tricolor holds its coiled neck just above the surface. A lightning strike captures its prey.

Like great blue herons, tricolors sometimes stand motionless, waiting for unsuspecting prey to swim by. At other times, the tricolor’s feeding behavior more closely resembles that of the frantic reddish egret. Dashing about, pirouetting and extending one or both wings, the tricolor is a frenzy of activity, stirring up killifish, topminnows and the like.

Normally, seeing an unexpected bird is great fun, but my reaction to seeing the tricolor was decidedly mixed. This bird shouldn’t have been there.

In the mid-20th century, ornithologists counted tricolored herons as the second most common long-legged wader in the United States (only outnumbered by cattle egret). In 1976, almost three-quarters of the U.S. breeding population was found in Louisiana (hence the bird’s old name, Louisiana heron). By the late 1980s, those numbers were plummeting. Wetland loss in the bayou was advancing at an alarming rate, robbing the birds of prime breeding and feeding locations.

Tricolors accelerated their search for new territory, rapidly moving up the Atlantic coast. In Maryland alone, 600 breeding pairs were counted in 2003. But even here, the habitat crunch continues. Isolated islands, prime breeding grounds safe from land-based predators, are being lost everywhere to rising sea levels and devastating storms.

The tricolor I was watching was apparently trying to adapt to a rapidly warming planet. It had arrived earlier and farther north than its ancestors ever did. Silently, I wished the bird well. But I knew full well that birds everywhere are being threatened by the climate crisis. The fossil fuel lobby and its enablers in Washington, DC, are handing tricolors and thousands of other species a life-threatening legacy.

If you love birds, fight for laws and regulations that will slash greenhouse gas pollution. Fight like their lives depend on it. Because they do.

The views expressed by columnists are not necessarily those of the Bay Journal.