Black-and-White Warbler, Dennis W. Donohue/Shutterstock
News and Perspectives on Bird Conservation
Amid Powerful Storms, Bahama Oriole Clings to Existence
By Cristina SantiestevanSeptember 08, 2017
Editor's note: As Hurricane Irma tore through the Caribbean this week, leaving a path of devastation across several islands, biologist Kevin Omland had his eyes on the Bahamas. The critically endangered Bahama Oriole, the focus of Omland's research, survives only on Andros Island in the western Bahamas. As he and other scientists try to learn more about these little-known birds in an effort to save them, powerful hurricanes are an increasingly problematic factor.
In the early 2000s, a series of hurricanes hit Grand Bahama, inundating the pine forests the oriole depends on, and last year the storm surge from Hurricane Matthew destroyed hundreds of acres of important pine forest habitat, says Omland, who is Professor of Biological Sciences at the University of Maryland, Baltimore County. Omland is leading a research project funded by American Bird Conservancy with support from the Bahamas National Trust.
Bahama Oriole by Daniel Stonko
Sea level rise and stronger hurricanes absolutely affect the orioles and other endemic and migratory birds in the Caribbean, ranging from Bahama Swallows to American Redstarts, Omland said on Friday. “Right now the storm's predicted track suggests the orioles may not get a direct hit. But the island of South Andros will likely see major impacts,” he said. This could include the destruction of such food sources as fruit, flowers, and insects, and longer-term impacts on pine forests.
This week's powerful storm could be “a great setback” for conservation efforts for the endangered oriole, says ABC's Philip Tanimoto, International Project Officer with ABC. “This underscores the great need for establishing a second population of Bahama Oriole on Abaco Island, where the bird occurred until the 1990s.”
Omland says he is most concerned about the Bahamians who take part in scientific research and help him learn more about this rare bird. “A storm like this is one more challenge to people's daily existence, and makes it harder for them to care about things like land-use planning and endangered orioles,” he says.
Read on to learn about some surprising recent discoveries by Omland's research team.
The Bahama Oriole has the unusual distinction of being designated a species not once, but twice. Can you explain how this happened?
In 1890, the Bahama Oriole was originally described as a distinct species. But during the 1940s and 1950s, people became convinced that the way to define a species should be based only on ability to interbreed. So the thing they created — the Black-cowled Oriole — included the Bahama Oriole, the Cuban Oriole, and several other species. They were just lumping a bunch of very different birds together. Upon closer inspection in the 2000s, scientists realized that these birds are all quite different from each other. Their ranges don't overlap at all and they have distinct DNA and different vocalizations. It's easy to tell their plumage apart, and now we think the ecology of the Bahama Oriole is also unlike those other orioles.
That happened with thousands of species around the planet, and certainly with hundreds of birds.
Bahama Oriole by Steven Brezinski
So, for 50 or 60 years, the Bahama Oriole did not exist as a recognized species. Did this have any impact on what we know about the species today?
Yes. Let's say someone is a birder and they go on a trip to Belize. They see a Black-cowled Oriole and they check that name off their list. So, when they get to the Bahamas later, they're focused on seeing the Bahama Swallow or the Great Lizard Cuckoo, but they figure they've already seen a Black-cowled Oriole. So maybe they don't make an effort to see it. It was during these years — specifically, in the 1990s — that the Bahama Oriole was extirpated from the island of Abaco. Nobody really knows when the last one was seen, by whom, or where. And I think that would have been pretty different if people were traveling to the Bahamas and checking off Bahama Oriole on their life lists.
So we don't know when the Bahama Oriole disappeared from Abaco. Do we know why?
We don't at all. It's a very complex story. There was a lot of logging done on all of these islands. Having those forests destroyed must have been very hard on the species. We now know that domestic feral cats are all over the place on these islands. There was also a disease that affected coconut palms called lethal yellowing disease. And then there was the arrival of the Shiny Cowbird, a “nest parasite” that lays its eggs in the nests of other species. These birds reduce the survival of the other species' nestlings. The bottom line is that there's a silent killer out there. Perhaps logging, lethal yellowing disease, feral cats, and/or Shiny Cowbirds impacted the birds on Abaco.
Overall, what has surprised you the most in your research on this bird?
Our biggest breakthrough was finding them breeding in the pine forest.
Last year, we hired a local assistant, Lehron Rolle, with funding from ABC. Before I got down there, he wrote to me and said, “I think there's one nesting in a pine tree.” I didn't think they would nest in a pine tree at all. But I had him show us the supposed nest, and there it was. Then one of my students, Daniel Stonko, found the birds nesting in thatch palm trees in the understory of the pine forest.
So what we're learning about the Bahama Oriole is really very different from what we thought was going on at the beginning of our project. It would have been a mistake to take action based on what we thought we knew two years ago.
Kevin Omland, left, and Scott Johnson on North Andros in May 2016. Photo by Daniel Stonko
Why would it have been a mistake? Do you have an example?
There were several important things we had wrong with our understanding of the species. We thought Bahama Orioles were dependent on coconut palms. People didn't think they used the pine forests at all.
There was this huge coconut palm plantation developed on North Andros, for instance. The people who planted the trees were excited because they were going to create Bahama Oriole habitat. In order to do that, they cut down acres of pine forest — a forest that we thought was not necessary habitat. Now we think there were probably several orioles that were using that stretch of forest that was completely clearcut.
If people had done that on a large scale we really would have been taking away the orioles' native habitat.
What's next for the Bahama Oriole?
We just completed the point counts from this field season, and we are optimistic that they are doing better than previous counts suggested. I would be surprised if there are not at least 600, 800, or even 1,000 individuals, up from the 140 to 260 previously estimated.
But we've only focused on one study site. If for some reason they are doing very well in our study site, but they're not doing well in other places on Andros, then my optimism would need to be tempered some.
Bahama Orioles at nest by Daniel Stonko
With these and other Caribbean species — especially as the climate changes — we need to have good population estimates and good monitoring in place. That way, when one of them, like the Bahama Oriole, starts to be really affected by more hurricanes, drier conditions, or more fires, we are then able to see those population changes and step in to address these threats.
We're going to need to learn a lot before we can get this species on the right track, and I don't think we know what the main threats are right now. This is really a project that is just beginning. We have learned just enough to know what research we need to do next.
ABC's support of the Bahama Oriole project is made possible through the generosity of David and Patricia Davidson, the Marshall-Reynolds Foundation, Stefan Williams, Christina Duthie, and ABC's William Belton Conservation Fund.
Cristina Santiestevan is an independent writer and editor committed to sharing stories about nature and conservation in today's world. She has written about the ecology of gardens, the myriad impacts of climate change and habitat loss, and the surprising conservation value of whale poop. Visit her blog at outlawgarden.com.