Dive-Bombing Terns: The Hassles of Being A Naturalist with Dr. David Wingate and Miguel Mejías

Exiting Flatt’s Inlet, Dr. Wingate spots a green turtle with its head above water, breathing for a moment before diving back down under the waves. “It’s rare to see those around here,” he says, and he retrieves a small pad from his breast pocket and begins scribbling a note. After he is satisfied with his observation, he explains, “I’ve been keeping a journal since I was 15.” Ever since that age, he has written down wildlife observations in the field, and has amassed a huge collection of descriptive data. He clarifies that some days have more notations than others. “My wedding day, I think I had one note – ‘got married today’ and that was it. I probably had a few bird observations too, my wife was upset about that,” he chuckles.

I had the chance to tag along with Dr. Wingate for his common tern observations. He explained that we would be visiting nesting birds in Harrington Sound to count and measure their eggs. However, he told me the eggs were unfertilized – the pair of birds tending to them were both female. “Their urge to breed is so strong that they still lay eggs,” he said, but they simply remain unfertilized. The lack of male Terns in Bermudian population is due to the differing migration habits of the sexes. Females migrate to avoid the hurricane season, while males may stay longer and become affected by it, selectively eliminating male birds from the population.

As we sped across the sound to an isolated island, Dr. Wingate warned me that the turns could be quite aggressive. He has been studying terns for about fifty years and taking nesting data, and he explains that the terns remember his boat and hassle him when they see him coming. “I got a new boat a few years ago and that fooled them for a while,” he says, but sure enough, when we approach the nesting island, two vicious looking birds sweep down close to the boat. Cutting the sky with their thin wings, they wheel high and low, making loud trilling distress calls from their bright orange beaks.

“You should be okay with a hat on,” he says, and soon I understand what he means. When we tie up the boat to the island and step onto it, the birds get more aggressive, and begin sweeping close to our heads, pecking us any chance they can get.

Tern breeding behavior makes their eggs very difficult to find, and Dr. Wingate warns me to take care not to step on them. Turns only nest on small, isolated islands colonized by low scrub in Bermuda. They lay their eggs on the ground, usually in a nest of dead purslane leaves, and rely on the specked camouflage of their shells to protect them. These habits make Tern eggs highly susceptible to hunting by rats, cats, or dogs, so they only inhabit island where these animals have not reached.

Soon we locate the five speckled eggs, lying on a notch on the bare rock. While Dr. Wingate handles them and measures their length and width with calipers, I write the data in his notebook. All the while, the Terns punctuate our work with their crisp alarm calls, and one swoops low enough to jab the back of my head savagely with its beak. While the Tern populations of other countries nest in vast colonies packed close together, Dr. Wingate has noticed that Bermudian Terns favour nesting individually. In a colony, the vast numbers of adult birds would act to deter predators from hunting any of the eggs, but the pair we visited likely learned to become even more aggressive in order to protect their single nest.

Terns do not need to incubate their eggs so much as they need to keep them cool. In fact, eggs can survive for many hours without being incubated. The scrubland where Terns nest does not offer much shade-providing vegetation, and the only way for adult birds to cool the eggs is to block them from the sun with their bodies. Dr. Wingate explains that there’s a huge risk in conducting Tern surveys in the heat of the afternoon, because it only takes minutes for the eggs to cook inside their shells while the parents are busy trying to chase researchers away.

Because the pair was female/female, and the eggs would never hatch, he wasn’t worried in this instance, but recalls times when it has been a problem. “They know that they have to be on those eggs,” he says, gesturing to the heat of the day and the white-blazing sun in the sky. While Terns usually defend their nests aggressively, Dr. Wingate explains, “I had a Tern once perch on my shoulder, it was almost like she was pleading with me, because she knew how quickly the eggs could die.”

The birds had laid a five-egg clutch, which is unusual for Terns, usually laying only three or four. Unfortunately for the mothers, none of them would ever hatch. Dr. Wingate explains his worries about Bermudian Tern populations – since he has been studying them, their numbers have dropped dramatically, and now we are down to two nesting pairs, one of which will never produce fertile eggs.

He explained that hurricanes are their biggest threat because they lay their eggs so close to the water. As global warming increases the strength of the storms, Terns are becoming more and more affected. After hurricane Fabian, we were down to only four nesting pairs. Only locally reared birds are sustaining the population, with little evidence of recruitment from other areas.

The only other nesting pair known by Dr. Wingate this year were located on the other end of the island, just off of Morgan’s Point. Before making the boat trip there, we picked up Miguel Mejías, an associate of Dr. Wingate who is now studying to get his PhD. Mejías has worked with longtails, spent time working with the Bermudian Tern population with Dr. Wingate, and is currently producing a research paper on Bermuda’s White Eyed Vireo. Mejías’ enthusiasm for ornithology exudes from his being so effervescently, it’s impossible to see him in any other field.

Mejías and Wingate take the long boat trip from BAMZ to the Tern nesting site near Morgan’s Point as an opportunity to spot more birds. As we cruise past the various small islands on the edge of Hamilton Harbour, Wingate catalogues all the Tern pairs who used to nest there. Due to the combination of hurricanes decimating nesting sites, along with rats colonizing islands and killing eggs, Terns have not returned to previously coveted sites. Lapstone, Dumpling, World’s End and many other islands have all now been quietened of Tern calls. Bermuda even has an island named after the Tern – Redshank Island in Harrington Sound. Redshank was the old Bermuda name for the Tern, due to its red beak and legs. Even here, on its namesake island, Tern nesting colonies do not persist.

“You’re not gonna believe where these Terns are nesting,” Mejías tells me incredulously as we approach. There seems to be nothing around here, except for a little, bare buoy, rolling and pitching in the waves. Soon, the Tern parents notice us and escort us, squawking, to their nest, astonishingly on top of the buoy. Dr. Wingate explains that they had to supply a nesting box full of sand for the parents to lay, and a shade box to shelter the chicks once they’d hatched. The buoy must only be about a meter in diameter.

Dr. Wingate explains that the workmen at Morgan’s Point were very cooperative with their conservation efforts. This pair of Terns had originally been nesting at the very end of their concrete pier. The workmen put up a barrier on the pier and left the Terns alone, but unfortunately, as the nest was connected to the mainland, rats found the nest and made an easy meal of it. The Terns didn’t want to move too far away, and ended up on the buoy. Dr. Wingate remarked anxiously that the chicks are very vulnerable there. When they start to fledge, it’s easy for them to be knocked off into the ocean where they will be doomed to drown.

These Tern parents had hatchlings about, and they were not going to give them up without a fight. Mejías leapt off the boat to retrieve the chicks, and endured the brunt of their attacks, as they bombarded him with well-placed shots of excrement, and swooped down close to make their piercing calls in his ear and catch him with their razor-sharp beaks. The chicks are easy to catch, because when they hear their parents alarm calls, they stay completely still. “It’s a great tactic on land, where they camouflage with the island, but useless here,” Dr. Wingate explains.

Heroically, Mejías returns with two chicks in a box, and two eggs; his back is splattered with bird excrement, but the smile on his face reveals he is none the worse for wear. The scientists then proceed with the banding and blood sampling of the two chicks. A numbered metal band is wrapped around the chick’s leg. “Their legs are at their fattest when they’ve just hatched,” Dr. Wingate says, so if the band is put on correctly, it won’t bother the bird for the rest of its life. All the while, Mejías holds the placid chicks while Dr. Wingate clasps the bands around their legs. They struggle very little, instead simply gazing up at us with inquisitive black eyes, “they’re good little chicks,” the grandfatherly Wingate gushes.

Earlier, Mejías had assembled vials of fixative in which to suspend the blood samples. The blood sampling process consists of pricking a prominent vein on the bird’s leg, and holding a capillary tube to the cut. “I hate this part,” Wingate says of pricking the chicks with a needle. Though it causes them momentary discomfort, the chicks can’t bleed out from the cut. Mejías lets the blood climb up the capillary tube, and then blows through the tube in order to transfer the sample into the vial of fixative.

The scientists repeat the process with the second chick, and Dr. Wingate accidentally pricks his own finger when a needle pokes through its plastic cap. He chuckles, “now I’ll probably catch some terrible Tern disease,” and was happy that his blood didn’t contaminate the sample. After replacing the chicks, finally at the behest of their parents, we turn our attention to what else Mejías removed from the nest. One egg is unhatched, and will not hatch this late in the season, Wingate proclaims. The other did hatch, but the chick must have died a few moments afterwards. We package up the chick’s carcass for Wingate’s study, and the two scientists measure the remaining egg.

As we leave, Mejías points upwards and grins – the two Terns are still following us. “They’ll follow us for a mile,” Dr. Wingate says. Though the scientist’s work disturbs the nesting Terns, it’s worth it for the important data they collect. Blood sampling sexes the birds and reveals insights about their DNA makeup, and Dr. Wingate’s study of Tern DNA demonstrated that Bermuda’s population is genetically unique and worthy of subspecies status. These findings were published in Conservation Genetics with the help of DNA specialist Patricia Szczys.

Dr. Wingate has become an expert in Bermuda’s Terns because of the long length of time he has spent observing them and banding them even before he began the blood sampling that lead to more in-depth study. “This is the best habitat for Terns in Bermuda,” he says, as we approach Pearl Island, a small outcrop isolated in the middle of the Great Sound. He explains that its secluded status means that rats won’t be able to reach it. In addition, it hasn’t been colonized by introduced species, leaving it covered by low-lying scrub, just the way Terns like it. The island is also higher out of the water than many other suitable habitats, making it a little more hurricane resistant.

When we get close to the island, astonishingly, there’s a Tern resting upon it. Dr. Wingate and Mejías flounder for their binoculars, and speculate over it excitedly. “Is it banded?” Dr. Wingate asks – if not, it seems a new individual has been added to our nesting population. After a few moments, they decide that it seems not to be a Common Tern, but instead a Roseate Tern, which haven’t nested in Bermuda for years, or even a hybrid of the two subspecies. Just when the naturalists were beginning to give up hope for Bermudian Terns, one turned up directly in the place Dr. Wingate thought it would. Once ashore, Mejías finds that it has laid a single, elongated egg on the rock.

“I would kill to get a blood sample of that Tern.” Dr. Wingate exclaims when we’re back on the boat. In the early years of the research project, they trapped adult Terns to band and blood sample, along with each crop of chicks. After a few years, however, the adults became trap-shy. Dr. Wingate hopes that he will be able to rig a trap on Pearl Island for the Roseate/hybrid. We didn’t see the other half of the pair either, and he hopes to return to the island to make further observations.