SWARA

The mesopredat­ors phenomenon and the role it may have played in the decline of the Taita Apalis. Rupi Mangat reports.

- Rupi Mangat

At first, the research team working in the cloud forests of the Taita Hills were in the dark about why nest failure of the critically endangered and endemic Taita Apalis ( ) was so high -- 90 per cent in Ngangao and 70 per cent in Vuria. The two forest relicts measuring less than two square kilometres are the stronghold of Kenya’s rarest bird.

Three years ago, with funding from the nature conservati­on charity RSPB, the team discreetly fitted camera traps by the nests of the tiny insect-eating songbird. Downloadin­g thousands of images caught on the sensory cameras, researcher­s found the culprits.

During the day, it is the African Goshawk ( ) preying on chicks and at night, it is the dormouse. Very rarely are these predators frightened off by a parent in the nest feeding the young. A few images showed the occasional snake making away with the loot.

THE MESOPREDAT­OR EFFECT – A COMPLEX WORLD

“What we are seeing might be the mesopredat­or effect,” said Luca Borghesio who has been studying the bird since 2011. He is a researcher with the National Museums of Kenya.

The mesopredat­or effect is when apex predators like big animals decrease, giving rise to the mid-size or smaller predators. These smaller predators take over the role of the apex predators, and in the absence of less competitio­n and conflict, they can go for more of the smaller prey -- in this case, birds like the Taita Apalis, driving them closer to extinction.

The images are helping researcher­s understand whether the predators are from within the forests or whether they are coming from outside the forest. They reveal details including if these birds were previously ringed and are

returning to the same nest to breed again, the kind of food they are bringing to the chicks, which makes for valuable data.

NEXT STEP

“It is important to confirm if this predation is a serious threat or not,” says research scientist Luca Borghesio. “That means we have to confirm the intensity of predation on the Taita Apalis. If the birds can nest faster than the predators can eat them, then the species can survive.”

It is therefore important to find out how many times a pair nests, and out of this how many nests are successful, and how many are lost to predation.

If the predation hypothesis is confirmed -- that most nests are being lost to the African Goshawk and dormice at a rate faster than the birds can breed, it is a problem.

“How do we control that?” ponders Borghesio.

HOPE

In April, 2019, in Iyale where a pine plantation has been allowed to revert to a natural forest, one Taita Apalis was seen in the restored patch. Iyale has only one recorded pair left in the forest.

“It’s a measure of success seeing the bird this far out,” said an elated

Lawrence Wagura, a member of the research team in charge of the forest restoratio­n. The idea is to reconnect fragmented indigenous forests that could throw the much-needed life support for not only the Taita Apalis but other species on the borderline like the Taita Thrush, Taita White-eye and even the local population of the African Crowned Eagle, increasing­ly on the wane.

“IT IS IMPORTANT TO CONFIRM IF THIS PREDATION IS A SERIOUS THREAT OR NOT,” SAY RESEARCH SCIENTIST LUCA BORGHESIO.

FACT FILE

Only three indigenous forest remnants that measure less than four square kilometres on the Taita Hills is home to the Taita Apalis.

Today some 200 survive from a population of 600 at the turn of the century. Most of the decline has happened as 98 per cent of the forests of Taita Hills has been converted to farmland, homesteads and forest plantation­s of exotic trees, in tandem with an increasing human population.

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African dormouse preying on the chicks of Taita apalis at night.
African Goshawk preying on the chicks of Taita apalis during the day.
Taita Apalis African dormouse preying on the chicks of Taita apalis at night. African Goshawk preying on the chicks of Taita apalis during the day.
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