Beachgoers playing volleyball on a small island at the mouth of Mobile Bay perpetrated a horrific crime in recent weeks, likely killing hundreds of tiny least terns.

The volleyballers even stacked dozens of eggs stolen from nests in a pile to bake in the sun.

Birmingham Audubon, which discovered the tragedy, hopes to use it as a teaching moment and further the group's effort to help Alabama's coastal birds rebound from the BP oil spill.

Least terns are the smallest of the terns, weighing 1.4 ounces as adults. They are about half the size of a cardinal, with snowy white feathers and a rakish black cap atop their heads. Their nesting style - laying eggs in shallow depressions on bare sand beaches - leaves them vulnerable to all manner of threats, from storm driven waves washing their nests away to predation by larger birds, or other animals, such as foxes.

Part of their evolutionary strategy to survive those threats is to nest in dense colonies of dozens or even hundreds of pairs of birds. The nests are close together, usually a foot or two apart. The speckled eggs laid in them are about the size of a grape.

That nesting behavior appears to have set the stage for the massacre, which was discovered by Andrew Haffenden, with Birmingham Audubon's Coastal Bird Survey. Haffenden, who was a wildlife researcher in his native Australia, was conducting a bird survey on a spit of land that juts off the south side of Dauphin Island.

Ironically, that spit of land was once Pelican Island, one of the best nesting sites in the northern Gulf for least terns and other beach nesters. But that was before the entire island migrated north and connected to Dauphin Island about 12 years ago. When the two islands merged into one, the birds quit using it for nesting because they were suddenly vulnerable to predators, such as foxes and feral cats that live in the forests of the larger island, and they were constantly interrupted by people walking along the beach.

During his survey of what used to be Pelican Island, Haffenden noticed several tents set up on a small island known as Sand Island about a mile offshore.

"I'd seen swirls of birds out there from the end of Pelican, and then on Fourth of July weekend, I counted 17 boats out there on that island, so I was pretty disturbed. I had been wanting to get out there, and looking through my scope, I could see the volleyball net and the tents. When we got out there in a boat, we discovered a colony of least terns and black skimmers that were nesting," Haffenden said. "Then we found the piles of eggs. The people had collected all the egg from the nests to clear out an area to play volleyball. The people had actually made a little dome of sand and placed the eggs around it to decorate it."

For beach nesting birds, especially in Alabama, the parents sit on their eggs not to keep them warm, but rather to keep them cool. Mobile Bay shares the same latitude as Cairo and the Sahara Desert, meaning the sun is brutal. Both chicks and unhatched eggs will perish in minutes left unprotected from the sun.

"The thing about the eggs, people think, 'oh, they're eggs,' but they are also almost fully formed chicks inside. They can walk almost as soon as they hatch," Haffenden said. "In that pile of eggs, there were a number that were about to hatch. In fact, if you look at the pictures of the pile you can see an egg that showed pipping (cracks where a chick is pecking its way out of the shell). What the people did was take those eggs away from the protection of the parents from the sun. So we had dozens of functional chicks die by being baked. It's pretty nasty."

"But it's not just the eggs in the pile; the amount of disturbance to the colony while playing volleyball, standing or sitting and watching the players would have at least a couple of hundreds females off the nest, which certainly caused the death of their hatchlings, and about to hatch and developing eggs," Haffenden said. "There were 17 boats on that tiny island."

Katie Barnes is the chief biologist for Birmigham Audubon's Coastal Program, which is funded through a grant tied to the BP oil spill. She is a lifelong bird lover. She wears a necklace that features dozens of birds in flight, and lives with the parrot she begged her parents for when she was a kid. (Parrots can live to be more than 100 years old, so she may have an avian roommate for a long time to come.)

"Immediately, we informed the U.S. Fish & Wildlife Service, because these are federally protected migratory birds. And we told the Alabama Department of Conservation and Natural Resources, which added the area to their patrol route," Barnes said. "The day after Andrew saw the net, we got out there and set up our symbolic fencing. (Symbolic fencing consists of a rope strung between posts, designed to discourage people rather than physically block them.) We got it all fenced off, posted with signs educating the public about the birds, and respecting the birds, and now they have a safe area to nest."

Audubon conducted a thorough survey of the tiny island, which features an elevation of about two feet above sea level. There were 520 active least tern nests and 13 black skimmer nests.

"What we've heard from the state is that may be the largest least tern colony on record for the state of Alabama," Barnes said. "Even with all the eggs that were lost, this site has still been a huge success for the birds. Ever since we put the fencing up, everyone has been very respectful. We have not seen a human footprint in the area. Boaters have not pulled up to that area. They are seeing the signage."

Sadly, high winds the third week of July appear to have taken a toll on the birds nesting on the island. It was clear from studying the wrack line of debris on the island that much of nesting area had been underwater for some period of time.

"A lot of nests were lost to overwash, but the last time we were out there after the storm, we had 65 fledgings. We've just added another 15 today," Barnes said. "It is a sand spit. There will be those natural occurences that kill birds. And there will be predation from laughing gulls and things like that. But, all in all, it was a success because these birds were able to raise their offspring. And we still have black skimmers actively nesting too."

Speaking of black skimmers, a word must be said about their outstanding parenting.

Black skimmers are big birds, as large as the biggest seagulls you see on the Gulf Coast. They have tremendous beaks, with underslung jaws that give them a sort of thuggish appearance. But as parents, they are quite attentive. I watched a pair of skimmers take turns sheltering their young chick from the sun. One skimmer would squat over the sand, breast down on the ground, and then use its legs to scoop out a depression. Once the scooping stopped, the tiny check would dash into the depression and nestle between the parent's legs. The parent would then settle down on top of its baby. After a few minutes, the baby would pop out and run over to the other parent, who would repeat the process.

Scenes like that make the devotion often shown by hardcore birders a little easier to understand. They are endlessly fascinating creatures. Both birds, and the birders.

Birmingham Audubon is looking for volunteers who'd like to help with their beach monitoring.

"They don't have to know a million birds or anything. If they can recognize a few key species, that's what we are looking for. We want people who can help survey, and people willing to man a table next to a nesting area," Barnes said. "Part of what we do is educate people. We want them to know the birds are out there, and what they are doing. That's how you make people care about the birds and do their best to help them along."

For information about volunteering, contact Katie Barnes at katiebarnes@birminghamaudubon.org.

Ben Raines specializes in investigations and natural wonders. You can follow him via Facebook, Twitter at BenHRaines, and on Instagram. You can reach him via email at braines@al.com.

You can watch Ben's most recent documentary, The Underwater Forest, here on Youtube.