There’s an uninhabited island in Biscayne Bay where a dozen species of birds whoop loudly in the treetops, stingrays nudge the shore, manatees linger and dolphins are a common sight.

It’s called Bird Key. And it’s covered in garbage.

From the waterline deep into the mangroves, there are tires, deck chairs, wood planks, beer cans, plastic bottles, children’s toys, fishing line, shoes, crates, coolers, plastic drums and an endless array of urban debris that Biscayne Bay swallowed up and spat out.

Sitting 500 yards offshore, just south of the 79th Street Causeway, Bird Key is one of Biscayne Bay’s oldest and most ecologically important islands. It was surveyed by the British crown and fought over by early settlers. Investors acquired it, and preservationists covet it. Yet little has been written about the island. And litter has been accumulating there for decades.

Formed by the outflow of the Little River, Bird Key is one of only two natural islands in the bay north of the Rickenbacker Causeway. At least 20 other uninhabited islands were created from spoil material dredged from the bay bottom when navigation channels were dug in the early 1900s. Those manmade islands serve as habitats for plants and recreation areas for boaters, but have little permanent birdlife.

Bird Key is different. It teems with brown pelicans, ibises, cormorants, ospreys, egrets, herons and other large native birds. They soar overhead, wade in the water, hunt offshore, nest in the mangroves and enliven the island with their loud, primal voices.

A surveyor sent by King George III to the British province of East Florida marked the spot on his map of Biscayne Bay in 1770. He called it Bird Island, a name that affirms its historic importance as a rookery.

It’s an important marine habitat, too. Dredged material was added to it in the early 1900s, creating a 2.6-acre parcel to the north of the natural 3.7-acre island. A natural quarter-acre islet sits next to the sandbar connecting the two islands, and they are surrounded by 31 acres of submerged land that contains endangered sea grass important to fish, shrimp, lobsters, sea turtles and manatees.

While the bay’s unoccupied spoil islands are government-owned, Bird Key is in private hands, a status that has its own complicated history and consequences.

The story goes that a Californian named Thomas B. Valentine won a 13,000-acre Mexican ranch in a poker game shortly before the Mexican-American War. When the war ended in 1848, borders were redrawn, and Valentine’s land wound up in U.S. territory. After a protracted legal battle, his claim to it was upheld, but by that time hundreds of settlers had established themselves on the land. As compensation, the federal government issued Valentine a stack of certificates or “scrip” entitling him to 13,000 acres of unsurveyed public land anywhere in the country.

Valentine sold most of those certificates. Worth 40 acres each and entitling holders to take possession of land the government normally wouldn’t sell, Valentine Scrip became a hot commodity. Some of it fell into the hands of Augustus Smith, a Florida attorney and reported con man, who used it in 1915 to claim Bird Key.

The state didn’t want Smith to have it. Neither did a real estate speculator who had been eyeing it. A young man who had been homesteading on the island challenged him, too. But, after two years of legal squabbling, Smith became the first private owner of ancient Bird Key.