For a glimpse of the diversity here, these transects have yielded well over 100 different species of birds since the project began in 2014. Remember, the 18 transects are just 250m long, each hosting fifteen 12m nets during the two mornings of operation for each visit, with two to three visits per season June to August. Furthermore, the nets are sampling only the 2-3m of airspace at ground level—in a forest with lots more airspace for canopy dwellers and vaulted ceilings stretching to 100m!

Spiderhunters

Let’s start with the bird we capture most frequently, Little Spiderhunter.

Spiderhunter species form a loose affiliation of sunbirds, a family of songbirds ranging from Africa to Australia, which occupy the nectarivorous and pollinating ecological niche filled by hummingbirds in the Americas. Like some hummingbirds, Little Spiderhunters “trapline” nectar sources in the forest, moving rapidly through the forest from one bundle of flowers to another along a memorized geographical route, much like a trapper checking traps. It’s this incessant lifestyle of rushing through the forest visiting low-growing ginger flowers that delivers it to our nets so often.

While Little Spiderhunter is abundant, other spiderhunters are unusual in our nets: some stay higher in the canopy, some frequent more open areas, and others may be specialized on less widespread flowers and thus scarce.

Kingfishers

North Americans and Europeans each enjoy only a single familiar kingfisher species among their continent’s avifauna. But tropical locations tend to host a diversification of species, from species even smaller than Europe’s Common Kingfisher to species larger than the North American Belted Kingfisher. And for many, their diets are much broader than just fish, harvesting insects or other invertebrates or even lizards off the forest floor. All of them seem to have been painted by artists trying to make a splash at the Paris Salon.

But the Rufous-backed Dwarf-Kingfisher, a tiny bird that is all beak, steals the show with its miniaturized stature and riotous scumble of improbable mauve-on-orange on the head and rump.

Each individual we catch startles anew. While we’re taking pictures to document molt and plumage details in order to characterize body and plumage development from fledgling to adult and to illustrate geographic plumage variation, it’s difficult to ignore their stunning color combinations from every angle.

Babblers…

Of course, I feel a need to foreground the project’s namesakes. After all, they do make up a significant portion of the birds we catch. Babblers are a challenging group. First of all, the taxonomic “family” was long an ornithological problem child. Ernst Hartert, a German ornithologist, described the family with a disdain reserved for misfits: "Was man nicht unterbringen kann, sieht man als Timalien an." (What can’t be assigned [to another family] is what makes up the Babblers). Such nomenclatural grab-bags have at times served as “wastebin taxa,” taxonomic placeholders for species and species groups with unresolved affinities. With recent genetic studies, extraneous groups have largely been excised and the concept of “babbler” split into two distinct but related families: Timaliid babblers (11 species on Borneo) and Pellorneid babblers (also called ground babblers or true babblers, with 19 Bornean species).

… & Bulbuls

Bulbuls are a more coherent family of birds than babblers, distributed from Africa to Asia, with a remarkable total of at least 23 species co-occurring on Borneo. Bulbuls are social and gregarious. That’s because for many, forest fruits and berries are a mainstay of their diet. Plants have an arrangement with bulbuls: they produce fruits as a vehicle to convey their seeds to new locations, while birds enjoy the fruit of their labor and pass the seeds along intact, lacking teeth to grind them with, unwittingly, with a little drop of fertilizer. Such an arrangement is mutually reinforcing: plants benefit from this active distribution network, so over evolutionary time, they may add nutrients to their fruit, or evolve attractive coloration, or produce a lot of it, or make it look like a lot, or fruit at times when other plants struggle to—any strategy to attract the birds’ attention. Bulbuls in turn have found a pretty sweet gig: plants producing fruit and vying for their attention means they can relinquish territorial aspirations and explore the wide world to seek out the day’s best fruiting opportunity—and party with all the other organisms making the most of the bounty, including lots of other bulbuls. As a result, the bulbuls most committed to frugivory are abundant in a diverse forest with a fruiting smorgasbord. Around the field station at Danum, we’re seeing a wide variety of fruits and berries ripening over the last few weeks. Bulbuls are ubiquitous—but in the canopy where the fruits are; they seldom fly low enough to hit our nets.

By contrast, babblers tend to be firmly tied to a territory they defend against other conspecifics. They’re securing “foraging rights” to a fixed area for food-finding: insects and other invertebrates don’t want to be found, so it takes time for babblers to scour the ground, twigs, leaves to find them despite their ingenious camouflage.

These are generalized observations; there are always permutations—ways of making a living that diverge from established patterns: new niches to be filled, novel combinations of food-finding techniques and parental care at the nest or fledgling stage, alternative strategies to exploit gluts and survive the lean season.

Eclectic Mix

And then there are so many more remarkable birds that make each banding day and every net check an exploration filled with anticipation: what will we encounter today? What surprise awaits us at the final net up that steep cliff—or down by the stream?

These are some of the mind-blowing creatures that animate these forests, left-to-right, from top left

Top Row:

Asian Fairy-Bluebird; Chestnut-capped Thrush; Blyth’s Paradise-Flycatcher.

Middle Row:

Blue-headed Pitta, female; Banded Broadbill; Asian Hooded Pitta, juvenile.

Bottom Row:

Dark-necked Tailorbird; Rufous-winged Philentoma; Lesser Green Leafbird.

Even the names are like poetry. Each one really warrants a mini-disquisition, wouldn’t you agree? But I can restrain myself. For now, I’ll have them speak for themselves. Enjoy the diversity of form and expression—we’ll save the disquisitions for another time!

That’s because the pedestrian suspension bridge over the Segama River connecting the Field Centre where the vehicle track ends to the unlogged forest reserve affords a spectacular view of the pristine forest. The bridge itself also qualifies as a bit of a scenic wonder and engineering marvel.

What’s so remarkable about Danum is the scale of the lowland rainforest reserve. On Borneo and in much of Southeast Asia, lowland rainforests have experienced dramatic human impacts over recent centuries: easily accessible compared to hill or montane forests, they’ve largely been logged or converted to plantations such as rubber (in the colonial era) or palm oil (more on that another time). That’s left few areas in the region with intact ecosystems to preserve the species that live there and to study how these systems work. When Danum Valley was protected—in 1980—there were no human settlements in the ~500 km² area. A much larger buffer zone around Danum includes selectively logged forest reserves.

When Suzanne Tomassi and David Edwards set up the long-term bird-monitoring study at Danum in 2014, the fundamental question they intended to address is the impact that selective logging has on bird communities and bird populations over the long term. To compare unlogged versus selectively logged forests, they set up 3 plots in each with three separate 250-m transects at each plot. To collect the bird data, the crews to this day simply set up fifteen standard 12-meter mist nets on one morning and then run the nets from 6am to noon on two subsequent days. Mist nets are used the world over to catch birds; by passively netting the birds in the forest—basically seining the understory air for what flies there—our captures provide a comparable sample of the species and their numbers from site to site and year to year. By marking them individually (with uniquely numbered rings/bands on their legs) and letting them return to their life after a short interlude in the net and in our hands, we can track site-faithful individuals over years of captures and generate an estimate of their survival rate with a little fancy math.

Upon arrival at Danum, our principal task with Suzanne was to locate all 18 transects and clear them for the 2m high nets and mark the access trails from the roadway. Through rain and sweltering heat, land leeches and no-see-um biting flies, Suzanne and Deddy, a long-time Research Assistant from SEARRP, were able to find shreds of old flagging, old cut marks on saplings and healed blazes on trees to identify the transects last used two years ago. Another SEARRP RA and two field assistants from Sabah with extensive ornithological experience whom we hired for the summer joined us for those tough first days.

When Suzanne started the project in 2014, civilian GPS units did not yet have sufficiently advanced antennae to reliably record locations in steep hilly terrain under a dense tropical canopy with (sometimes) thick cloud cover. I know, because we faced precisely the same problem on a similar project I conducted in the Jaguar Preserve in lowland rainforest in Belize for a grad student at the University of Massachusetts at Amherst. But recently, the “technology” (antenna sensitivity? Satellite density? Triangulation algorithms?) have improved so much that regular Garmin GPS units record fairly precise locations. So I recorded waypoints along each transect at each of the plots along with the access track routes and some of the roadways. So now we each can view all 6 plots on a base map or topo map using a Garmin app on our phone either at the regional scale (with two of the virgin forest plots walking distance from the Field Centre—where the blue arrow shows my current location) or zoomed in at a much finer scale. It is astonishing what our phones are capable of!

There is a lovely old-fashioned analog map as well, showing the trail system around the Field Centre from about 30 years ago.

Our third unlogged forest plot is a long drive on another track that leads to one of the fanciest ecotourism lodges I’ve ever seen, the Borneo Rainforest Lodge (BRL). In order to secure access to the plot, we met with the new director of the lodge who takes a selfie with his meeting guests for documentation. He indicated that we would be welcome to lunch at the lodge restaurant after our field days—provided no other guests were around. He know only too well what our condition might be after a morning in the forest.

The attractions that draw in tourists from all over the world to BRL, of course, are incredible encounters with wildlife on their trails, on the canopy walk, and even at times along the access road. The suspension bridge at the Field Centre, though, offers not just a focal point for the Centre’s built environment, it also doubles as a kind of canopy walk, observation tower, and river walk. Recently, for example, a clan of smooth otters passed by under me as I crossed the suspension bridge on my return from plot two.

And shortly thereafter on the Field Centre side, an Orang-outan made an appearance with its slow deliberate movements through the subcanopy. It seemed to be looking for a good spot for the leaf nest they build every afternoon to spend the night in.

To save on costs, I found an excellent deal from Seattle to Singapore—using Alaska Airlines miles on Qatar Airlines with a stopover in Doha. For an incorrigible birder like me the prospect of a stopover in a new airport, new country, always creates an extra frisson of anticipation: what exotic birds that I’ve never encountered before might I detect during the layover? Admittedly self-indulgent; incorrigible, as I said. On top of that, there is the frisson of concern that pulling out binoculars and scouring runways with fierce determination might trigger the worrying type among my fellow passengers to “see something, say something.”

Doha was gleaming, clean and somehow both opulent and sterile at the same time. Nevertheless—or maybe as a result—I managed to cultivate a certain ominous foreboding from the ads and displays.

Even the birds disappointed: House Sparrow, an introduced Myna, and Laughing Dove.

Singapore’s Changi airport, on the other hand, is both over-the-top and stunning.

Finally, the preparatory team members met up in Kota Kinabalu, one of Borneo’s destination cities on the Northwest coast and a gateway for tourists chasing adventure diving offshore, climbing Mount Kinabalu or stalking elusive wildlife. Julia Weiss, a PhD student at Cambridge in Professor David Edwards’ lab, had been on weekly zoom calls with me since October 2024, but we hadn’t met in person. We invited Suzanne Tomassi to join us for the first two weeks of the season, mainly because we recognized that running a season of the long-term bird-banding study at Danum is such a complicated undertaking that her experience and site knowledge simply could not be transferred without her presence. Together with David Edwards, she conceived of and set up the long-term bird-banding study in 2014, and she ran it for eight field seasons until 2023 (with CoVid disruption).

Kota Kinabalu is a necessary stop on the way to Danum for researchers to collect signatures, permits and authorizations. Suzanne’s help finding the offices for “Commissioners for Oaths” and at the government office buildings proved invaluable—I just hope we can manage on our own in future seasons! Someone with earlier experience had suggested bringing a box of chocolates or some-such to ease along our transaction at the Sabah Biodiversity Centre (SaBC), but clearly what perhaps once may have been standard operating procedure had received critical attention from higher-ups!

Finally, with permits in hand and visa complications sorted out (you don’t want to know, or maybe we are not at liberty to say)—and after easing along our own transactions with a mysterious box of chocolates—we boarded the one-hour prop-jet flight from Kota Kinabalu to Lahad Datu, a town on Sabah’s east side which also serves as the supply center for Danum Valley. With a final stop at the office for the Danum Valley Study Centre, which manages the field site in conjunction with SEARRP (Southeast Asian Rainforest Research Partnership, an NGO originally established by the Royal Society in 1985 that coordinates research activities at Danum and other sites—yes it’s THAT complicated), we picked up our trusty project vehicle, a classic Toyota Hilux, and headed a short distance up the Pan Borneo Highway before turning inland through oil palm plantations and then on a winding dirt track 80km through selectively logged forest to the field station at the edge of the famed virgin lowland rainforest reserve.

What you jettison may turn out to be something you really need. Everything you take ought to be essential—but maybe not the gear that can be sourced locally. And well into the field season, you’re faced with the stuff you really wish you had: the thermometer normally in your personal first aid kit that somehow slipped out, flagging you planned to get for marking trails. Any of the decisions you make along with all of the accidental oversights can have consequences. A thermometer might have shown that my fevers three weeks in were severe enough to go see a doc ASAP—rather than wait 4 days to see if the symptoms passed. But the flagging? Team members had enough to tide us over and Danum staff were able to snag some extra at a hardware store in town.

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Babblers and Bulbuls sound like new characters on a kids’ show. They’re actually two groups of birds that make up a major portion of the forest birds on the island of Borneo.

1. Borneo

Borneo, the third largest island on our world, straddles the equator, so it’s a hot place. Three modern countries share the island. The Federation of Malaysia includes two states on Borneo, Sarawak hugging the northwestern coastal slope and Sabah capping the northern tip of the island, like a toupee. All of the small nation of Brunei, an oil-rich sultanate, is tucked onto the NW side of the island, near the northern end of Sarawak. The rest of the island—and the majority of its landmass—is Kalimantan, one of the states of Indonesia. The island hosts dramatic mountains; much of the interior consists of steeply mountainous ridges stretching from little-known ranges along the southern end all the way to the northern tip, culminating in Mount Kinabalu at 4,095m (13,435 ft) on the north end of Borneo, the highest peak in Southeast Asia between the Himalayas and New Guinea. For hikers compelled to bag craggy peaks, be prepared for the cold up there—no glaciers or even snow fields, but temperatures at night can drop below freezing.

2. Evolution on Borneo

A large equatorial island with so much geographic variation is a spectacular laboratory for evolution. Evolution, the process by which living beings develop and change over time, remains a driving force that continues to adjust the way organisms interact with their surroundings, their environment. On Borneo, all that geographic variability with all the diverse geologic substrates bathed in equatorial heat and torrential rains generates a profusion of opportunities for living beings to, well, make their living: harnessing an energy source underexploited by others; mobilizing nutrients before someone else does; weathering the heat and the dry, the rain and the wet; cooperating where possible, competing when necessary; and storing if they can what they need for a life worth living—metabolizing, interacting, reproducing, those fundamental functions characteristic of life.

Understanding how life works is the mission of biology as a scientific endeavor. One basic step in that process is simply inventorying what’s there. On Borneo, that systematic process is still very much underway.

Even among birds our basic inventory is still expanding, yet birds are often our most familiar co-inhabitants on earth, because they are mostly diurnal like us and share our sensory world at scale in the visual, aural and tactile realms.

The B&B Project is my effort to give the activities of ornithologists—scientists that study birds—public-facing exposure, as we go about our work to learn how birds operate by collecting data systematically on them in their free-living state in the world, where the choices these individuals make—what we call behavior—determines their fate day to day, season to season. Much of our work is inscrutable to the general population—we keep crazy hours, we manage risks that are unusual in most people’s lives, we submit to environmental exposures intolerable to ordinary folks, we venture into physical geographies that don’t tend to warrant visits from most people. Sharing our narratives, not just our data, can offer vicarious experiences that travelers and tourists—and even adventurous locals—wouldn’t necessarily encounter, thereby enriching lives and offering an expanding volume for our collective imaginations. Join me on these adventures, won’t you?

To get this blog going, the whole team at Danum this 2025 season will post about our experiences at our field sites and around the Research Center. We hope the images of the incredible birds we’re marking and releasing will attract your attention—and that you’ll linger a bit to learn more about Danum, tropical rainforests and their complexity; about the highlights—and pitfalls—of field research; and the social community both at a remote field station and nearby communities.

We hope you’ll share your thoughts, too! And comments with your questions can serve as an impulse for a future blog entry. Subscribing ensures that you don’t miss an amazing bird or some new drama—I intend to keep them thoughtful and content-rich, providing background and context, not just a one-off bird pic at a time… We intend to post 2-3 times per week as field work allows; new posts will deliver a notification to your email.

As the blog develops its style and a following, I’ll expand this Substack to include exclusive content for paid subscribers—along with the 60 supporters of the original Babbler & Bulbul Kickstarter campaign, which is actually underwriting a portion of this season’s expedition! The themes of the free blog will remain dedicated to field biology, science and birds, while the Substack content for paid subscribers will dive into deeper themes such as:

• Evolution and mechanisms of speciation

• Science in society and the crisis of truth

• Ornithosophy, or Thinking like a bird

• Reading birds as cultural touchstones

In challenging and inauspicious times, exploring this remarkable world more deeply—with all its beauty, mystery and passion—offers opportunities to transcend the vicissitudes that buffet our daily lives. Try it, and come explore with me!