* The next few posts will deviate a little from my normal format and represent a bit of nature travel escapism for those of us feeling a bit cooped up these days. The previous episode ended with my arrival at the Joburg airport and collection by Justin and Ben, with whom I would be working for the next 5 months.
The four-hour car ride from the Johannesburg airport to our new farm home and basecamp in the hills outside Pietermaritzburg passed in a blur of highway medians and sleep-adled haziness. When we did arrive at the gated entrance to the farm, I managed to coax my brain up from the depths of its stupor to take note of the surroundings. The landscape was a matrix of sprawling grassland, forested riparian patches, cattle pastures, and pine plantations layered upon an undulating terrain of hills and valleys. I don’t remember the dimensions now, but the farm must have encompassed hundreds if not thousands of acres.
As we drove down the mile-long dirt driveway, we excitedly pointed out the new birds to one another, and gawked at the cows lazily watching us drive past. We eventually came to the primary farm compound which consisted of a main house and a smattering of smaller buildings and sheds tucked into the outlying trees. The owners—a British South African couple-- came out to greet us, accompanied by their two young daughters and four dogs: two enormous wolfhounds, and two darting terriers. As I came to learn during my time in South Africa, this sort of canine combination is quite common. The small dogs (with their acute hearing) serve as an early-warning alarm system in case of trespassers, and the big dogs serve as a deterrent with their chomping teeth and slobberous quantities of drool.
After the introductions, we were shown to our living quarters, which were in a self-contained apartment unit attached to the main house. I was pleasantly surprised at the accommodations; up to that point in my field biology career I had only ever lived in a tent during field seasons, and hot water was used for cooking, not bathing. Here, however, we were in the Taj Mahal of field houses. Not only did we have beds, a kitchen, and a shower, we had access to the sparkling, sublimely chlorinated waters of the swimming pool just outside our doors. A guy could get used to this, I thought happily.
The first few days were spent getting familiar with our new realm, and delineating where we would focus our work efforts. Waterbuck (a large antelope), duikur (a genus of small to medium sized antelope, ranging from 6 lbs. to 150 lbs.), lizards, an abundance of frogs and toads (many sporting white “racing stripes”), technicolor grasshoppers, giant winged antlions, and myriad new bird species were our field companions as we traversed the grassy slopes and valleys.
We dodged semi-concealed holes in the ground that were the product of burrowing aardvarks, and were constantly on alert for venomous snakes like spitting cobras, black mambas and puff adders. Our target was the nest of the common waxbill, a small, mostly gray-brown finch with a fiery red mask and orange-red bill. Males are also adorned with a splash of red on their belly and chest. As I mentioned in the previous post, common waxbills are hosts to the brood-parasitic pin-tailed whydah, which is another small-bodied finch. Male whydahs, however, are boldly patterned in black and white, with long black tail streamers that are 2-3 times the bird’s body length. Males show off these streamers during mating displays in which they bounce up and down in the air in front of a female. Females are a much less ostentatious brown and tan-bodied bird, with some black streaking thrown in for camouflage in grassy environs. Once a female has selected a sufficiently attractive bouncing male and mated with him, she heads off in search of waxbill nests to deposit her eggs.
I can tell you from experience that locating a waxbill nest in the grassy expanse of the South African midlands is no easy task. Waxbills build grass nests that are woven into the bases of living clumps of grass. These nests are completely enclosed, with a secret grass-tunnel entrance. As if that weren’t challenge enough, they tuck these small globular grass structures underneath a visually impenetrable barrier of overhanging grass tussocks. So what you end up with are essentially invisible grass nests scattered across a seemingly endless grass sea. For an extra psychological kick in the groin, these birds actually seem to derive pleasure in taunting nest-searchers. Unlike most small passerine birds, waxbills appear to have no qualms about venturing far outside any localized home range or territory. On countless occasions during my searches I came upon waxbills with strands of grass in their bill, only to watch them take flight and disappear over a distant ridge, giving me a parting smirk just before they vanished. But even more soul-crushing was watching a bird disappear into the distance with a beak full of cat poop.
Yep, you read that right. Waxbills engage in some bizarre scatological behavior in which they weave carnivore droppings into the outer walls of their nests. They seem to prefer the scat of small to medium-sized wild cats like servals and African wild cats. These felines consume a lot of small mammals, which means that their scat is usually composed of tightly compacted strands of small mammal fur that the waxbills artfully incorporate into their nest. Servals and African wild cats are extremely secretive and rather uncommon, so their scat is a hot commodity for the waxbills. Finding a waxbill with a cat turd in its beak was a joyous occasion because it meant the bird was headed directly back to its nest. When I encountered a be-pooped waxbill (like bespectacled, but with poop in its bill), I would immediately morph into commando mode, dropping to a knee, fixing the binoculars on the bird with laser-like intensity, and preparing to sprint after the bird should the need arise.
The nest of a Common Waxbill. The opening on the top is actually a false chamber, presumably meant to fool nest-predators. The actual entrance is the cascading tunnel dropping down in the front. Notice the carnivore scat at the opening to the false chamber. Also, this is a particularly conspicuous nest. Most were practically invisible. KwaZulu-Natal, South Africa. Photo credit: Justin Schuetz.
It’s hard to appreciate the degree of mental anguish associated with failed nest-searching when you spend long days out in the intense African sun, plodding across boundless grassy slopes without locating a single nest. As such, the stakes feel very high when you find a bird preparing to bring home some new housing décor. However, even when everything goes according to script—the bird carries its prized possession only a hundred meters and drops down into a very identifiable patch of grassland where you can pinpoint the location at which the bird vanished from view—you can fail to find the nest. These birds are masters of visual ventriloquism (if such a thing exists); you think it went one place, and discover later that it is in fact somewhere behind you. The best you can do in these circumstances is to mark the general area that the bird vanished, retreat a hundred meters and place the entire area under surveillance. If that doesn’t succeed, you return another day hoping to perhaps flush the bird from its nest. And if that fails, you curse the birds and the nest-searching gods and move on.
The curious reader will want to know why waxbills go to such lengths to defile their nests with the excrement of an animal that would happily consume them and their offspring. Cat scat, it turns out, deters nest-predation from one of the waxbill’s greatest nest-enemies; small mammals. It may come as a surprise to learn that small mammals can act as nest-predators, but many species of rodent will happily augment their normal vegetarian diet with eggs, and, on occasion, an unfortunate young nestling. (It’s kind of like the “ovo-pollo” version of vegetarianism, which, if we’re being honest, isn’t actually vegetarianism at all.) Because common waxbills nest on the ground, it is thought that they are at increased risk of nest-predation from small mammals. By adding bits of cat feces to their nest, however, they make their nest smell like a small-mammal-eating machine. To test this theory, Justin (the grad student I was working for) did some observational and experimental work examining the efficacy of having carnivore scat in the nest. He found that every natural waxbill nest that successfully fledged at least one chick contained carnivore scat, and that experimental nests with scat added were significantly less likely to get depredated (eaten) than nests without scat. A fascinating rendition of the adage “(the droppings of) the enemy of my enemy is my friend.”
So, having dealt with the small mammal issue, waxbills are left to contend with the parasitic whydahs. Compared to the more virulent cuckoos and honeyguides I covered a few posts back, whydahs are relatively benign. The female whydah sneaks into a waxbill nest, lays an egg, and leaves. She may return to deposit another egg or two, but she doesn’t eat or destroy any waxbill eggs, and once the whydah chicks hatch, they don’t push the other occupants out or pierce their cervical vertebrae. On the whole, they’re rather ok for uninvited houseguests. Whydah nestlings are a bit larger than the waxbill nestlings, and according to some sources they beg more vociferously for food, which may allow them to outcompete the smaller host chicks. But in many instances, the adult waxbills are able to raise all their young, along with the parasites. Where things get interesting is when we take a look into the mouths of these nestlings.
The family of birds to which the waxbill belongs (Estrildidae) is composed of over 100 species spread across Africa, Asia, and Australia, and includes some well-known members of the pet trade, such as the zebra finch and Gouldian finch. The pin-tailed whydahs are in the Viduidae family, which contains about 20 species found throughout Africa, all of which are parasites on Estrildid finches. Many of the Estrildid finch nestlings have startling bright and bizarre markings inside their mouths and lining the flanges of their beaks, and the markings of each species are generally quite distinct. Except, that is, for the markings inside the mouths of the corresponding Viduine parasite. Take our common waxbill and pin-tailed whydah duo; the whydah may parasitize other species, but the common waxbill seems to be the most frequently parasitized host, and the whydah appears to have evolved a remarkable degree of mimicry regarding the mouth markings. When we look at other host-parasite pairings, a similar pattern emerges, resulting in a dazzling example of co-evolution between the two lineages of host and parasite.
But one of the intriguing, and still unanswered questions about these mouth markings is why Estrildid species that are not parasitized (such as those in Australia) also have these elaborate markings. As is usually the case, there are a few possible explanations. One is that the ancestral Estrildid finch had mouth markings, and that as species split and diverged, the markings split and diverged with them. But what purpose would the markings have served in the absence of brood parasites? Well, for one, they could act as targets for the parents inside the dark, enclosed nests that many Estrildid finches use; a “Food Goes Here” sort of beacon. The markings could also be an indicator of the chicks’ condition, allowing adults to preferentially feed the highest quality chicks when resources are limited. In his study, Justin found evidence in support of the idea that the markings are important signals to the parents. He used a non-toxic marker to manipulate the mouth markings of the waxbill nestlings to see if the parents would adjust their behavior towards the chicks with different markings. It seems that they do. While they did not eject the nestlings with the altered markings, those chicks with modified patterns experienced slight but significant reductions in growth, suggesting that the parents were providing more food to the unmanipulated chicks. This finding also provided some evidence for a selective pressure on the parasitic birds to match the markings of the host; without the right mouth pattern, the parasitic nestlings risk getting passed over by the host parents.
Over the course of the three and a half months of searching for waxbill nests, I think I found about 50 nests. It might have been closer to 70, but if we do the math, it was likely less than a nest per day on average. On most days, that didn’t matter. I was, after all, traipsing around South Africa, looking for nests, and thrilling to everyday encounters with wildlife I had only ever seen in a museum or on TV. One day, while watching some suspicious waxbill activity, a duiker came loping through the grass and nearly ran into me before noticing I wasn’t a large boulder. On another occasion I watched a blue duiker squeeze through an opening in a fence. I know that doesn’t sound noteworthy, but when I went to look at the opening the duiker had crawled through, I saw it was no bigger than my fist. Apparently, the limiting factor on the size of an opening a duiker can fit through is its skull, and the little blue duikers have awfully small skulls. I also saw dozens of new bird species, as well as exciting new reptiles and amphibians. But it wasn’t always a walk in the park.
I suffered a few bouts of mild heatstroke, one case of food poisoning (never leave leftover Indian food in the car in the African summer… and then eat those leftovers later), and an annoying allergic reaction to, of all things, the sun. That’s kind of like being allergic to the wind, and it doesn’t work out well if you’re a field biologist. Essentially the problem comes down to a rapid transition from no UV exposure (like what you have in Maine in November) to high UV exposure (South Africa in their summer). And the way my body responds to this perceived insult is to burst into hives. Heat and humidity (both available in sizeable quantities in South Africa at that time of year) exacerbate the condition, as does more sun exposure. For me the issue is most pronounced on my hands, which are hard to keep covered out in the open grasslands. And once the hives are out, they do not like to be stuffed into a pair of gloves or any other covering. Unfortunately for my hives, one of the sites we worked at once or twice a week was a recently cleared section of pine plantation that was transitioning into a giant bramble thicket, and a good pair of gloves was critical for wading through the sea of thorns. This site was called Hilton, but it quickly became Hell-ton, and I dreaded our trips there.
Aside from these few annoyances, the field season passed quickly, and for the most part, enjoyably. Before we headed up to Tanzania (via Egypt) for the next leg of the field project, we had a few weeks of adventure travel to enjoy. I’ve already touched on one of the elephant encounters, but in the next post we’ll visit with rhinos, hippos, and a huffing honey badger.
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About the author:
Loren grew up in the wilds of Boston, Massachusetts, and honed his natural history skills in the urban backyard. He attended Cornell University for his undergraduate degree in Natural Resources, and received his PhD in Ecology from the University of California, Santa Barbara. He has traveled extensively, and in the past few years has developed an affliction for wildlife photography.