The sky is bright blue and a cool breeze blows across the savannah as we load into the field rover for a morning’s fieldwork session. Last night’s electric rain shower brought a renewed sense of prosperity to the land, and the air is thrumming with joy and thumb-sized African beetles. Like tiny helicopters, they attempt to land on our shoulders and heads, attracted to the bright colored ties we wear in our hair.

They’re harmless enough, but our guide warns that the insect’s nickname, ‘blister beetle’ is well earned for the welt it can deliver.

“Just duck, it’s cool—it’s like Jedi training,” says David Millican, our guide and researcher extraordinaire.

We’ve followed him to what could be considered the middle of nowhere—just outside of Otjiwarongo, Namibia. But the truth is, despite the low human population it’s quite definitely a somewhere: a beautiful rocky and sandy landscape brimming with biodiversity. Some of the world’s most rare and unique animals—cheetahs, giraffes, jackals, aardwolves, leopards, hornbills, and much, much more— call this harsh climate home.

Today, we’re accompanying David on a trip to check for cavities—and not the painful trip-to-the-dentist kind. We’re looking for bird homes: holes and rips in tree trunks and branches that are used by bird species within the local cavity guild. While the guild consists of bird, mammals, and reptile species, we’re most interested in the feathered ones.


As a bird biologist, David has a nagging question: which types of tree cavities are the birds using? By recording the species of birds that reside in different types of cavities, we can also determine who may be in competition. Finding the answer to these questions will help him answer larger ones about the structure and dynamics of the guild community.

David has established 20 sites across four adjacent farms that he believes could harbor a significant amount of tree cavities. During this season’s fieldwork he will repeatedly visit the sites, which are 16 hectares, to monitor cavities he’s discovered and search for new ones.

Acacia trees—which are abundant in these parts—are a favorite nesting spot. Some of the cavities we will visit were created by lightning, broken limbs, and insects or fungal decay. But others—known as excavated cavities—are pecked and created by the birds themselves. The birds that create the holes are known as primary excavators and the birds that live in the holes another bird created are known as secondary nesters, according to David.

“Some cavities can take a while to excavate, especially in live trees,” says David.

David’s tools today are a ladder, a peeping camera, a handheld GPS system, and a notebook for recording our findings.

He uses the GPS to navigate through his seventh site— a scrubby grassland of fallen brush and thorny plants, littered with a few antelope skulls.

Using the ladder to climb up to the first cavity resting high in the tree, David sticks the long cord of the peeping camera into the hole and is able to see on his monitor what awaits inside. This time, it’s nothing.

However, a few cavities later, we see signs of a former nest: feathers and grass. David’s hopes are lifted.

On the way to the next cavity, a cacophony of peeps arises from a tree ahead.

Those are alarm calls,” says David, pointing in that direction. “That means there is likely a predator is nearby—could be a black mamba, boomslang, or mongoose. It’s best for us to go around that area.”

Working our way around the commotion, we come to a beautiful old camel thorn tree with a long slivered cavity in the trunk, about eye level . David inspects the hole with delight. Part of it is caked over with a thick mud: the telltale signs of a hornbill nest.

When female hornbills are ready to nest, they will enter a cavity and caulk themselves in, closing up the hole with mud, millipede shells, grass, and other vegetation. This is to prevent predators from entering and disturbing the nest when both babies and mom are vulnerable: moms lose their wing and tail feathers when incubating eggs and cannot fly.

Carefully and quietly, David sticks his cord into the small opening that remains and watches his monitor. Three timid faces stare back at him. Nestlings! And not very old at all, judging by their pink, featherless alien bodies.

David points the cord upwards into the hole and sees a fluff of feathers that he determines to be the mother, a yellow-billed hornbill. Often the mother will move to an area with more space above the cavity floor, allowing her to climb above the cavity entrance if a predator tries to break in.

David quickly retracts the cord. We will leave this nest alone for now, tiptoeing away quietly to avoid upsetting the sweet family.

Written by Lindsay Key/Photos by Jelena Djakovic.