Private Biscayne Bay island, bird sanctuary for sale

A private island in Biscayne Bay has hit the market for $31.5 million.

Why it matters: Bird Key, located just south of the 79th Street Causeway , is considered environmentally endangered and has long been a sanctuary for native birds, the Miami New Times reports .

• It is one of two naturally formed islands in the bay north of the Rickenbacker Causeway, per the Miami Herald .

Driving the news: The 4-acre island, which was listed for sale April 26 , is being advertised as a 37-acre "residential opportunity," including the submerged lands surrounding it.

• "It is a golden opportunity for a developer to acquire and use for environmental mitigation, or one could acquire it to donate it to the public as an environmental treasure, or finally a very lucky individual may create Miami's most exclusive address, because this gem is zoned residential," the listing says.

Friction point: Miami-Dade Mayor Daniella Levine Cava tells the New Times that the county offered to purchase Bird Key in 2023 but was turned down.

• "We are eager to find alternatives, including state or federal support, to purchase this property and expand the footprint of our Biscayne Bay protection programs," she told the outlet.

Flashback: The island has served as an important bird habitat since at least 1770, when a British surveyor named it Bird Island, according to the Herald.

• The property changed hands a few times in the last 100 years, eventually being purchased in 1985 by Edward Easton and Finlay Matheson of the pioneering Matheson family .

In 2012, Matheson told the Herald he wanted to see Bird Key become an official bird sanctuary.

• "I think the highest and best use is to sell it to a developer who needs it for environmental mitigation."

Yes, but: Matheson now tells New Times he's not concerned about its fate and urges prospective buyers to make an offer.

• "[Bird Key] has been sitting idle for a long time. There's lots of activity on the market," he told the outlet. "Now's the time."