Bahamas Dry Forest Journal

When you look up close at the exterior of the Havana Cathedral, you can see the shapes of brain coral, seashells and ancient marine fossils.  The cathedral was built from coral bedrock, carved out of the nearby bay, a reminder that while some aspects of this baroque Jesuit cathedral borrow from the old world, these famed Havana buildings are firmly rooted in the West Indies.

Above is a new map of the Abaco Islands, which I drew to give more detail and in order to better explain the region I most explored this time around.

Great Abaco, the larger of the two Abaco Islands, is one of the largest landmasses in this region - it's the tenth largest island in the Caribbean Basin; larger than many more well known islands such as Martinique, Saint Lucia, Dominica, Grenada and Barbados. To drive from Crown Haven in the north to the isolated end-of-the-road known as Hole-in-the-Wall is 112 miles.

It is also one of the least populated and slowest growing populations in all the Caribbean. Only about 13,000 inhabit the Abaco Islands year-round, and so in an off-season like this November, beaches are empty, roads are empty, and the places that are empty even at peak season are really, really empty.

Note the area I depicted as "Dry Forests" north of Treasure Cay, as well as "The Marls", which is a vast network of uninhabited mangroves, islands and saltwater flats. The intersection of these two habitats is not well explored, written about or even understood, and its in this zone that I spent most of my time walking.

I've never seen a Kirtland's Warbler, the tiny yellow and black bird that nests in the American midwest and winters thousands of miles away, but it's not because I haven't tried.  

When most people look for the Kirtland's Warbler, it's during the summer in a stand of Jack Pines in the state of Michigan.

But each year, I look for the Kirtland's Warbler in the Northern Bahamas.

It wasn't so long ago, I remember, when nobody was really sure where the Kirtland's Warbler, one of the rarest birds in North America, wintered.  This mystery was one of the reasons that prompted me to join Dr. Woody Bracey on some of his forays into the Abaco Islands outback, where over the past several years, he and a handful of other birders and naturalists were starting to see the birds with increasing frequency.

Dr. Bracey's sightings over the years prompted a team of ornithologists to contact him.  I joined up with the team for a day as Dr. Bracey led the team through the northern part of the Abaco Islands, explaining the habitats where he's seen the birds in the past.  This gave me the opportunity to interview three members of the team.  

Joseph Wunderle of the US Forest Service, Dave Ewert of The Nature Conservancy and Nathan Cooper, postdoctoral researcher for the Smithsonian Migratory Bird Center, are part of a surveying team moving through the islands of the Bahamas in order to learn about the winter ecology and habitat of one of North America's endangered species success stories.

Erik: The Kirtland's Warbler is in many ways a success story of conservation, and yet, there are still fewer than 5,000 individuals left.  Why is this species important?  How large should the global population be before conservationists stop worrying about it?  

Dave Ewert: The Kirtland's Warbler population was probably never large because of its very restricted range on both the breeding and wintering grounds, so a population of 5,000 birds may not be very different from pre-settlement populations.  The species is important as it is a prominent part of the jack-pine ecosystems of northern Michigan, it attracts birders from around the world who contribute to the local economy, and it is one of the first species listed as endangered in the United States.  It is an iconic species with a devoted following.  The recovery goal of 1,000 nesting pairs of Kirtland's Warblers over 5 years has been met and the species is being considered for de-listing as an endangered species.  Should the global population fall to 1,200 pairs (currently it is about 2,000 pairs), a bit higher than the recovery goal, this would trigger increased efforts to prevent further population decreases.  

Erik: I would imagine the massive interest in birds creates opportunities for funding in a similar way that elephants or pandas do, but I would also imagine there are countless plant and animal species that get little attention.  How might warbler research benefit other species?  Is the Kirtland's Warbler an umbrella species?  

Dave Ewert: The Kirtland's Warbler is an umbrella species for the jack pine ecosystem as nearly 200,000 acres are devoted to management for the species and, as a result, habitat requirements of co-occurring species are met.  The management applied to the Kirtland's Warbler benefits many other species, such as white-tailed deer, snowshoe hare, Upland Sandpipers, Eastern Bluebirds, Hermit Thrush, Palm Warbler, and many others.  Blueberries are common in the understory. 

Erik: A member of your team has been physically banding the warblers.  How do you actually capture, and then band these Kirtland's Warblers?  Wouldn't such a device impact this tiny, one ounce bird?  

Joe Wunderle: Kirtland's warblers are captured using mist nets, fine mesh nets that the birds often don't see.  In many cases they are drawn to the nets by using playback of song and call notes, which attracts birds to the net.  The birds are extracted from the nets and then fitted with  a small aluminum government band with a unique number.  A unique combination of color bands is also applied to the bird to permit individual recognition of the birds without capturing the bird, thus minimizing stress to the bird.

Bands have been applied to thousands of species of birds and studies have compared survivorship of birds with and without bands and shown little or no differences in survivorship between banded and unbanded birds.  
Erik: One member of your team is a plant ecologist, and earlier, you described your research as being about the habitat of Kirtland's Warblers, rather than the bird itself.  How can you study the habitat of a species with few chances to see the species in its wintering grounds itself?

Dave Ewert: Based on early research where few Kirtland's Warbers were seen, we assumed that the likelihood of finding birds was very low. Accordingly, we designed a study to examine how common species respond to winter conditions during early, mid and late winter, to account for increasing drought as winter progresses, and then we intended to extrapolate results from this study to the Kirtland's Warbler.  However, the ornithology group of Bahamas National Trust, discovered a concentration of Kirtland's Warblers on Eleuthera, which allowed us to study the Kirtland's Warbler, and its' habitat requirements, directly.  Based on what we learned at this site, and nearby sites, in Eleuthera, we found many more Kirtland's Warblers elsewhere on Eleuthera and on other islands, and thus gained a much better understanding of the ecology and distribution of the Kirtland's Warbler in the Bahamas archipelago.  

Erik: Other warblers travel deeper in Latin America, while this bird winters so close to the U.S.  Why is the winter habitat of the Kirtland's Warbler such a mystery?  

Joe Wunderle: The primary reason the winter habitat of the Kirtland's Warbler was mysterious is that they are very difficult to detect on the wintering grounds.  Several factors contribute to the very small number of sightings in the Bahamas.  One is that the population is very small so the probability of encountering a Kirtland's Warbler is low compared to virtually every other  warbler species that winters in the Bahamas.  Further, they inhabit dense scrub, remain low in this scrub, and vocalize infrequently so they are hard to detect.  Consequently little was known about the winter habitat until we found enough birds to characterize habitat and thus develop a "search image" for habitat  which resulted in finding more birds and further refinement defining winter habitat.  

Erik: You have all spent years as researchers in other parts of the Caribbean and Latin America.  With your knowledge of the forests and jungles of Puerto Rico or the Virgin Islands, for example, what is your impression of the forests of the Northern Bahamas? Did you see anything unusual or that particularly struck you about these forests?  

Joe Wunderle: The large expanses of Caribbean pine forests are very different than forests in most other parts of the caribbean.  Though the pine forests have been heavily used, these pine forests are among the highest quality Caribbean pine forests as they are largely uninhabited, natural processes such as fire and hurricanes maintain the forests, and they are relatively unfragmented on Andros, Grand Bahama and Abaco.  They support species found only in the Bahamas, such as the Bahama Warbler, Bahama Yellowthroat, and Bahama Swallow, and other species with a small global range, including Olive-capped Warbler and the Bahama Parrot.

They have a distinctive character with considerable variation in understory due to the frequency of fire, proximity of the water table to the surface, and past land use.  

New geolocation technology has been pushing small-bird research in new directions.  Your team has been adding geolocators to Kirtland's Warblers in Michigan.  But in order to use that data, you have to recapture that bird back in the United States.  Is this like finding a needle-in-a-haystack?  What can the data from a limited amount of recaptured birds tell you?  Any surprises in the data?

Nathan Cooper: It's actually not like finding a needle-in-a-haystack, because Kirtland's Warblers (and most other birds) are quite faithful to their breeding sites each year. Some birds move between breeding seasons, what we call breeding dispersal, but often only on the order of hundreds of meters. However, many birds come right back to the same spot each year, sometimes even nesting under the same tree. This makes our job much easier. We put out sixty geolocators on males last year, and we are realistically hoping to get about half of them back. Adult male survival is ~60% from year to year, so about 36 of them should come back next year. The hardest part will be catching them all again!

We placed the geolocators across their entire breeding range in Michigan. Twelve birds at five different latitudes. This should give us an idea of migration speed, migration routes (potential differences between fall/spring migration), and an overall idea of their migratory connectivity. This refers to how birds on the breeding grounds disperse onto the wintering grounds and vice versa. So a species with strong connectivity would involve all the birds from one part of the breeding grounds migrating to one part of the wintering grounds. This information is really crucial if we are to conserve migratory species and has many implications. For example, imagine a hurricane came through Abaco, and wiped out all of the wintering habitat. Would this harm the population in just one part of the breeding grounds or have a much more diffuse effect across the breeding grounds?
No surprises yet, but we only have data back from a few birds.

Erik: How do you physically attach these geolocators to the bird, and does it affect them in any way?

Nathan Cooper: We use an elastic material to make a backpack of sorts. The loops of the pack go around the bird's legs and the device sits on their back. This way their wings are unaffected and they can fly freely. The devices only weigh ~0.5 g, or less than 5% of the adult mass. This is the rule of thumb for attaching devices on birds. Several studies have looked at how this might affect their behavior and survival. In most species, Kirtland's included, the survival rates of birds with and without devices are not significantly different.

Here is one of Nathan Cooper's videos attaching a radio transmitter to a nestling:

The process is almost identical for an adult except that you have to hold them much tighter since they are stronger and trying to get away the whole time.

Erik: How exactly can this tiny device geolocate a bird?  Can they do so with any accuracy?

Nathan Cooper: We use light-level geolocators. These devices measure light intensity to get two values - day length, and time at solar noon. From this one can determine both latitude and longitude. There is certainly some error around these estimates due to a variety of factors (e.g., cloud cover, shady vegetation, elevation, time of year), but give us a position, give or take to a hundred-fifty kilometers. There are some newer GPS geolocators that use GPS satellites to determine position. These are much more accurate, but not yet light enough for a bird like a Kirtland's.

Erik: Under ideal conditions and with a larger sample of data, what do you hope to be able to learn about the Kirtland's migratory routes?

Nathan Cooper: Ideally we'll have GPS geolocators that are light enough for a Kirtland's. This would allow us to not only better describe their migratory routes, timing, etc., but also determine exactly what types of stopover habitat they are using during migration. Migration accounts for more than half of all mortality in this species so understanding habitat needs, routes, etc. Are really important for understanding how, where, and when Kirtland's are being limited. It is important to note that even though most mortality occurs during migration, events prior to migration can be really important. These seasonal interactions have been shown to be increasingly important by researchers at the Smithsonian Migratory Bird Center and elsewhere.

Erik: Travel bloggers often write about the Bahamas as if it were a big casino resort or cruise destination.  But your team is spending weeks inside the country's forests.  Are travel writers describing The Bahamas accurately?

Joe Wunderle: Tough question.  From the perspective of many tourists the portrayal of the Bahamas as a resort or cruise destination may be accurate even though it is not representative of the character of the country.  From our perspective, the diversity of ecosystems, variation within those ecosystems, and the associated nuances of Bahamian culture, is largely, and unfortunately, missing from write-ups of many travel bloggers.  It would be great to have increased emphasis on the unique features of the bahamian landscape and how critical it is to protect these landscapes, as the natural resources of the country obviously provide the foundation of Bahamian culture and the tourism industry.  

How I Extended the Range of the Pearly-Eyed Thrasher

Jane and I were returning from our rental unit after having picked up a supply of water from the grocery store in Treasure Cay, Abaco, Bahamas when I noticed something just slightly off in the form of a bird on an electricity wire.

Mostly, the electricity wires in Treasure Cay come complete with starlings, doves and blackbirds. But this bird had that look about him. You know that look, that in stories we attribute to crows and vultures and condors? That look of slight villainous wisdom?

Still, we had just arrived in town and I put the bird out of my mind.

But again, the next day, as I walked back into town, I again saw the bird, looking down at me with that poisonous looking eye of his, and I began to churn it through my mind. What is this thing? Do Red-legged Thrush juveniles have an odd plumage? Is this a roughed-up Mockingbird?

Later that evening, I went through all the birds of the Northern Bahamas, and came up blank. One thing that birding and identifying species has taught me is the reality of the false visual. When we see things fleetingly, our minds connect the dots differently - our minds can construct a false memory around a fleeting glimpse of something. We see a bird, and our mind builds it into something.

With that in mind, I decided to give up, once again, on the strange bird.

A few days later, Jane and I were walking into town again, and lo and behold, this strange, slightly villainous bird is looking down at me from a ficus tree. With my binoculars, I can see it clearly. That villainous eye; a cool piercing bluish-tinged eye, is not so villainous as distinct and beautiful.

There is no doubt in my mind, this is a Pearly-eyed Thrasher, a bird which has never before been seen on this island, nor anywhere close.

I handed my binoculars to my wife, who said, 'that looks like a thrasher', and 'It has a sandy color', and 'a whitish eye.'

We kept walking, and again I began to doubt my own eyes.

Returning to our rental unit, I immediately emailed Dr. Woody Bracey, the local expert on birds and one of the most accomplished birders of the West Indies. I was cautious in my email. "Woody, have there ever been thrashers seen on Abaco?"

He replied, "I found a Brown Thrasher in November and it stayed about 3 weeks and left before our Christmas count."

I typed back, "I am certain I saw a Pearly-eyed Thrasher..."

But Woody didn't respond, and I could understand why - I'm a casual birdwatcher making an extraordinary claim. When I saw him a few days later, I took the subject up again. I had once witnessed Woody interview locals in South Abaco who had claimed they saw a rare bird. With keen questions, he stripped them of their sighting. And I knew he was about to do the same with me.

"Is it possible you saw a Bahama Mockingbird with a bad case of glaucoma?" he said.

I insisted on my sighting, and I kept referring to Jane's words. Jane's words meant that my mind wasn't just reconstructing something. They were an independent confirmation of what I saw.

Later that day, Woody and I met up with a team of ornithologists from The Smithsonian, The US Forest Service and The Nature Conservancy who were conducting research on warbler habitat. Woody recounted my apparent sighting, and, later in the day, the entire team agreed to visit the site in Treasure Cay.

The Pearly-eyed Thrasher was gone.

But one of the lead researchers, who had spent years in Puerto Rico and the Virgin Islands, at the heart of the Pearly-eyed Thrasher's range, said, "You know, I don't doubt his sighting at all. It is quite possible. Looking at this area, I am convinced this is perfect habitat for the Pearly-eyed."

He talked about the species' propensity to push its range, aggressively pursuing new habitats. As human civilization expands its use of plantations and fruit-bearing trees and shrubs, the Pearly-eyed Thrasher has reason to extend its range.

That was enough to convince Woody to keep visiting the spot. A day later, he found and photographed the Pearly-eyed Thrasher.

In doing so, we added a new bird to the list for the Northern Bahamas, created the northernmost sighting of the species and effectively pushing the northern terminus of the bird's range to a latitude north of West Palm Beach.

As a bird species list for any island grows, that island grows more intoxicating to the high-end birdwatching traveler, and the ebird data map story changes just a little bit for any researcher studying the species.

Back home here in Oregon, where there are many birders and ornithologists, records like this rarely happen, or at least when they do happen it is almost exclusive to the most accomplished birders.

But the fact that a casual birdwatcher can create such a record by sheer accident explains something important about the Abaco Islands and the Northern Bahamas in general. This place is still a wild west of naturalism and discovery.

Each time I fly over The Abacos and Grand Bahama, I see countless miles of coppice woodlands, mangrove forests and pine barrens. Has anybody ever walked through all of those places? It is possible to look down at an expense of wilderness, and like few other places in North America, wonder if anybody has ever been there.

In fact, finding the Pearly-eyed Thrasher so thoughtlessly in the middle of a resort town is a reminder that those unexplored woods likely hold many more discoveries.

Travelers have this picture of The Bahamas as these islands just off Florida. Big resorts, waterslides, casinos. But that is a false image of The Bahamas isolated to just one island. The Bahamas is better seen as a vast, marine and forest wilderness, threatened by development, but still wild.

Coppice Forest is the local phrase to describe the dense, stunted forests of the Northern Bahamas and the Turks and Caicos. Growing up, I had little respect for the Coppice. The forests looked impenetrable in the way that dense thickets or brambles in the states might be. I held this view even though, in actuality, having grown up somewhat in these islands, I actually played with my brothers often in this type of habitat.

After thirty-five years of visiting the Abacos, I have begun to see the coppice as one of the most magical aspects of these islands. Yes, they are dense and barely navigable. Yes, the forests have few tall trees, and most are dry and tangled. But the reality is that coppice forests, which scientists now call Bahamian Dry Forests, are places of incredible wonder. My sketches and photographs from this visit to the Abacos will attempt to share some of that wonder.

One species I keep running into in clearings inside the coppice forests is a brilliant orange, white and black moth, that when it opens its wings, shows a striking pink. This is the Ornate Moth, or Utetheisa ornatrix.

Ornate Moths are studied for their sexual selection practices. Females mate with many males in their short, one-month life as adults, and males offer the females nuptial gifts - packages that contains not only sperm, but food and essential alkaloids.

This small butterfly, the Atala, with its electric blue and chinese orange colors, is one of the most vibrant denizens of the Northern Bahamian dry forests. It was once believed to have become extinct in Florida, because of the decimation of its host plant, the Coontie. But the species has begun to flourish in Florida where the host plant has been reintroduced, and is one of the finest symbols of the importance of these easy-to-dismiss habitats.

My friend at RollingHarbour.com has very good information and life cycle photography on the Atala.