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Tracing Africa’s ‘fading biological fingerprints’ in Angola’s threatened forests

Evolutionary biologist Gabriel Jamie photographs a Huambo cisticola. Image by Ryan Truscott for Mongabay

  • Angola’s Afromontane forests are considered to be the country’s most threatened habitat type due to logging, wood harvesting and fire.
  • Experts say the forests are relics that harbor “fading biological fingerprints” from a previous epoch.
  • It’s not just species living in the closed-canopy forests that could be threatened by the loss of this ecosystem, but those that live alongside them.
  • They include the Huambo cisticola, a species now known to be unique to Angola that lives in the ecotone, or transition zone, between forest patches and surrounding grasslands.

MOUNT MOCO, Angola — “Another one incoming,” shouts ornithologist Michael Mills to his colleague crouching a few meters away on the flanks of Mount Moco, Angola’s highest mountain. “Oh heck, it’s gone over the top.”

The small brown bird with a pale breast and ginger crown had already twice bounced off a mist net strung between two aluminum poles and nearby bushes along a narrow, slippery mountain path flanked by bracken, grass and shrubby sand olives. Mills and University of Cambridge evolutionary biologist Gabriel Jamie had captured the bird’s mate and were hoping to trap him too.

Jamie plays a recording of the bird’s distinctive call, a series of high-pitched whistles and trills. Within minutes the male bird returns and is trapped in the net — but only for an instant: he escapes through a hole.

The Huambo cisticola is a small insect-eating bird that feeds and lives on the edges of Afromontane forest patches. It is most often seen in places like Mount Moco and the nearby Namba Mountains. Image courtesy Michael Mills.
Gabriel Jamie (right) and Michael Mills set up a mist net on Mount Moco to catch Huambo cisticolas. Image by Ryan Truscott for Mongabay

Protecting a unique and dwindling habitat

The site of all this activity is a patch of restored Afromontane forest growing above the village of Kanjonde, at the foot of Mount Moco, in Angola’s western Huambo Highlands.

The birds the two scientists are trying to catch are Huambo cisticolas (Cisticola bailunduensis), a species that favors the edges of evergreen forest patches just like this one.

Decades of firewood harvesting and uncontrolled wildfires have left most of Mount Moco’s forest patches severely diminished. They now cover a total area of less than 85 hectares (210 acres), sharply down from an estimated 200 hectares (about 500 acres) in the 1970s. Nevertheless, they still harbor a suite of forest-dependent birds. Some, like the Huambo cisticola, are found only in Angola.

Mills runs a conservation project with the help of local villagers to restore Mount Moco’s remaining forest patches by surrounding them with protective firebreaks and replanting trees in degraded areas so that forest birds can once more move within them, up and down the mountainside.

For Jamie, a bird in the hand on Mount Moco is worth two in the bush.

Holding the single captured Huambo cisticola in his left hand, he uses his right index finger to gently moisten a patch beneath her wing, then pricks an exposed vein with a needle, and uses a capillary tube to draw out a blood sample. He uses the end of the tube to paint lines of blood across circular patches on a card impregnated with enzymes that will preserve the bird’s DNA. For good measure, he places an additional drop of blood into a tiny tube of ethanol.

The DNA sampling Jamie is doing on Mount Moco is part of his wider research into cisticolas, a genus composed of more than 50 species found mostly in sub-Saharan Africa, and their responses to being targeted by a brood parasite: the African cuckoo-finch (Anomalospiza imberbis). Cuckoo-finches have a habit of laying their eggs in other birds’ nests, getting the latter to do the work of incubating them. While they’re known to do this to various cisticola species, and while they do occur on Mount Moco, it remains to be seen if cuckoo-finches are targeting Huambo cisticolas at this site.

“We know the cuckoo-finches mimic the eggs of their hosts, and in response to being mimicked, the cisticolas evolve this amazing egg diversity within each species,” says Jamie, who’s also affiliated with the University of Cape Town’s Fitzpatrick Institute of African Ornithology.

“Cisticolas have the most diversely colored eggs of any group of birds in the world,” he says. “It’s all in response to being parasitized by cuckoo-finches.”

The Huambo cisticola was previously identified as a subspecies of the rock-loving cisticola (Cisticola emini), a bird that lives in semiarid savannas north of the equator.

“In 2008 when I was here [in Mount Moco conducting a bird survey] and heard it, I knew it had nothing to do with the rock-loving cisticola,” Mills says. “It looks different, it sounds different and it behaves differently.”

Though BirdLife International and the IUCN already recognize the Huambo cisticola as distinct from the rock-loving cisticola, the data Jamie gathers on the species’ DNA will provide further confirmation.

Although occasionally found in well-wooded gullies elsewhere in Huambo province, the cisticola is most often found in the transition zone, or ecotone, comprising grasses, shrubs and bracken around the edges of the forests in Mount Moco and the nearby Namba Mountains.

“In the absence of the forest, presumably the ecotone would go as well, and the habitat wouldn’t be there,” Jamie says. And that won’t just be bad news for Huambo cisticolas.

Western green tinkerbirds, (Pogoniulus coryphaea). Image courtesy Michael Mills.Namba Mountains. Image by Ryan Truscott for Mongabay.Angolan slaty-flycatcher (Melaenornis brunneus). Image courtesy Michael Mills.Margaret's batis (Batis margaritae). Image courtesy Gabriel Jamie.Bar-tailed trogon. Image courtesy Michael Mills.Swierstra’s francolin (Pternistis swierstrai). Image courtesy Michael Mills.Kanjonde women carry seedlings. Image by Ryan Truscott for Mongabay.Mistletoe, Mount Moco. Image by Ryan Truscott for Mongabay.Ross’s turacos (Musophaga rossae). Image courtesy Michael Mills.Bocage's akalat. Image courtesy Michael Mills.

 

Africa’s Afromontane forest archipelago

The forest patches here and in the Nambas total less than 700 hectares (1,730 acres). Yet, biologically speaking, they remain vitally important relics of a widespread and contiguous ecosystem that spanned Southern, East and Central Africa during a previous geological epoch, experts say.

“After surviving 2.6 million years of climatic oscillations through the Pleistocene, the relict Afromontane forests of Angola are shrinking ‘sky islands’ in an ocean of fire,” writes South Africa-based conservation scientist Brian Huntley in his 2023 book, Ecology of Angola.

Compared to similar forests in Tanzania’s Eastern Arc Mountains, or the rainforests of the Congo Basin, the Angolan forests are “minute and fragile specks,” he writes. “The biota of the forests represent fading biological fingerprints.”

One person who can vouch for that is Martim Melo, a biologist at the University of Porto’s Research Center in Biodiversity and Genetic Resources. Melo has surveyed the Afromontane forest patches on Moco and in the Nambas, and studied the birds they share with other Afromontane forests thousands of kilometers away.

“It’s the only habitat or biome in Africa that occurs in this archipelago pattern, in isolated pockets,” he says. For Melo, the Angolan portions hold a critical piece of evolutionary history. They acted as a “stepping stone” between the much larger Afromontane forests of East Africa, and those in the Cameroon highlands to the west.

“Angola played a central role in the evolution of at least the bird fauna of these [Afromontane] centers,” Melo told Mongabay in a May 2023 interview.

“We also saw, when you reconstruct the past climates, that on many occasions Angola [provided] the most stable conditions for the forests, and this might explain why for some species of birds we have very old lineages that, with further study, we might split into separate species because they’ve been there for a long time.”

Melo was part of a group of scientists who last year warned of the threats that uncontrolled fires posed to the forests in the Namba Mountains. Unlike those on Mount Moco, there’s nothing being done to protect them from burning.

Yet the Namba Mountains still host at least four species of birds that have gone missing from Moco as result of historic forest disturbance on the mountain. If the Nambas’ forests are kept safe, reintroductions of Moco’s missing birds could be done with populations that persist there.

Meanwhile, back on Mount Moco, Jamie finishes collecting data on the captured Huambo cisticola. After putting her inside a cotton bag and weighing her on a digital scale, taking exhaustive measurements of her bill, claws and feathers with a set of battery-operated calipers, and photographing her from every angle, he releases her.

She flits away unharmed into dense bushes. Numerous attempts to catch more cisticolas by shifting the position of the mist nets are unsuccessful, and then work has to stop as another thunderstorm rumbles over the mountain.

“I think science is mostly about persistence,” Jamie says with a grin as he scurries for shelter from the rain.

A forest restoration project brings birdsong back to Angola’s highest mountain

Banner image: Evolutionary biologist Gabriel Jamie photographs a Huambo cisticola. Image by Ryan Truscott for Mongabay.

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