MARRERO — As the cloak of early morning fog blanketing the entire West Bank began to dissipate, a group of about 25 bird-lovers headed into the swamps of the Barataria Preserve for the annual winter bird count.

From swamp sparrows hopping across waterlogged cypress knees to turkey vultures circling high above the towering oaks, the preserve, part of the Jean Lafitte National Park and Preserve, is host to more than 300 species of both resident and migratory birds.

The volunteer-driven event held Saturday began with a safety briefing about the dangers in the swamp. The most dangerous creature is the disease-carrying mosquito, said Dave Fox, park biological sciences technician. Copperhead and cottonmouth snakes, fire ants, mama alligators tending to their young, and poison ivy were among the other potential perils to watch for, Fox said.

The group was divided up into smaller teams, each with at least one experienced birder, to cover the nine miles of walking trails in the 23,000-acre park. By 9 a.m., the wintery breath of morning air was quickly dissolving into a warm springlike day with temperatures reaching into the 70’s.

Counting the birds every year is important for monitoring the vital signs of the ecosystem, Fox said. Environmental change can be detected by studying several groups of species, including birds, which are easily visible, Fox said. The numbers gathered Saturday, including a nighttime owl count, will go into a local, regional, and national database, he said.

Armed with binoculars and bird books, former park ranger and English professor Wendy Rihner began her count leading a group along a short stretch of La. 301. The morning air was bursting with bird sounds. There were melodious songs, screeching calls, chirps, squawks, twitters and taps. But only the ear of an expert birder — such as Rihner’s — could quickly distinguish and identify the species.

Rihner called out to the group’s record keeper. “Give me one yellow-rumped warbler,” Rihner said. “Make that two. And one blue-gray gnatcatcher.”

Rihner demonstrated “spishing,” a spish-spish sound birders make to agitate the birds so that they can be more easily seen or heard. “It’s not a very nice thing,” she said, but useful, as the birds scolded her back from the trees.

In the bottomland hardwood forest along the highway, Rihner and her team identified mockingbirds, red-bellied woodpeckers, eastern phoebes, American robins, and yellow-bellied sapsuckers. A barred owl hooted in the distance. As the Carolina wrens called out boisterously, Rihner said that her husband calls her a wren because the birds are “so small, but so loud.”

One of the volunteers headed into the trees and flushed out a noisy flock of red-winged blackbirds — conservatively marked as 20 on the data sheet. Glints of vivid red fluttered in the tangled branches as cardinals flew from tree to tree. High above, the wide white wings of a great egret gracefully flapped against the bright blue sky.

When a bird flies directly into the sun and cannot be identified, Rihner said, they are called “sun birds,” and not to be concerned about.

The diversity is a good sign of a healthy ecosystem, Rihner said, in that it shows the area can successfully host a variety of species. Each species has its different needs, and different “niches,” she said. Keeping track of the resident and migratory birds can also provide information about the overall robustness of the ecosystem, she said, and that birds are truly the “Canary in the coal mine.”

And at the end of the day in the bird world, Rihner said, it’s all about sex and eating. And the different species have different personalities — from aggressive to noisy to easily upset. Rihner said the ruby-crowned kinglets are particularly macho, but not as macho as hummingbirds.

Watching a distant group of black vultures circle in the thermal updrafts, Rihner said, “That’s so awesome — how can you not envy that?”

Transitioning onto the Bayou Coquille trail that winds through forest, palmettos, swamp and marsh, the birders spotted orange-crowned warblers, and gray catbirds.

The volunteers squinted, pointing at the tree branches strewn with wisps of Spanish moss where perched Carolina chickadees, red-shouldered hawks, crows, and blue jays, and tufted titmouses.

“We ended up with 28 species,” Rihner said, “The most numerous wintering migrants were ruby-crowned kinglets, yellow-rumped warblers, and eastern phoebes. And we had the usual large numbers of residents species: Carolina chickadees, vultures, and Carolina wrens. So it was a nice mix of winter migrants and year-round species. Just what I anticipated.”

As for Rihner, she said her love for birds is inspired by “the freedom they have.” She said she also loves their colors, their beauty, their songs, as well as the opportunity to get outside and meet “fantastic people.”

As the winter day grew almost balmy, with puffy white clouds and abundant sun glistening on the murky waters of the swamp, Rihner resolved that, “I can’t think of anything better to be doing on this day.”