There is a buzz among bird enthusiasts as a special red knot named Moonbird was spotted in Delaware Bay last week. This is no ordinary red knot. He's been called "the toughest four ounces on the planet" because he is the oldest known member of this species at at least 21 years old. Researchers don't know exactly how long red knots live, but they do know that with an average annual migration of 20,000 miles, this particular bird has lived long enough to fly to the moon and more than half way back. And that's how he got his nickname.

Moonbird was fitted with an orange B95 tag back in 1995. Since then, researchers have spotted him each year, and each year think it will probably be the last time they'll see him. But here he is, defying the odds, spotted yet again by Argentinian researcher Patricia Gonzalez at Reeds Beach, Cape May County. "None of us ever believed that B95 would live to be 21 years old and just keep going as strong as ever. But here we are," Charles Duncan, a Maine conservationist, told Philly.com. "And now I think none of us would dare bet — 25? 30? Who knows?"

Moonbird has become a celebrity representative for this species, the decline of which underscores the complex web by which humans are attached to and impact everything else. As red knots make their annual journey from Argentina to Canada, the long and arduous journey requires a short stop off on the beaches of the east coast, including Delaware Bay. Their arrival is perfectly timed with the arrival of horseshoe crabs, which come ashore to lay their eggs by the millions. These famished birds fill up on the eggs, refueling for the rest of their journey. Without this food source, the birds can't make it to their breeding grounds. There is only a short window of time, and the fact that they arrive within that window is amazing. However, their numbers have plummeted in recent years as humans have over-harvested horseshoe crabs. The red knot population at Delaware Bay dropped from about 100,000 to just 12,000 in 2003. Thankfully, a preliminary count for this year shows about 26,000, which means efforts aimed at the conservation of beaches, horseshoe crabs and red knots may be working.

If you're interested in learning more about Moonbird, conservationist Phil Hoose has written a book, "Moonbird: A Year on the Wind with the Great Survivor B95."