Translocation of “predominantly females” to Chawia forest will help avert imminent local extinction of the Taita thrush population there, conservationists say
I remember last year when someone remarked rather dramatically, “I hear they have a shortage of females in Taita”. Seeing the confusion on our faces he added, rather cheekily, “The birds, the Taita Thrush”. I chuckled, thinking, “The birds and the bees didn’t prepare us for this!”
Later, I learnt that the females of Taita Thrush had not been seen or captured in the Chawia forest fragment of the Taita hills for the past four years – despite intensive mist netting – posing something of a problem for the thrush subpopulation there. I filed that fact away, until today when an email announced a translocation initiative to re-stock the forest with females.
Photo: Thrush with transmitter and inset, being ringed. Courtesy of Mwangi Githiru (species guardian)
The Taita Thrush, Turdus helleri, is a forest-dependent endemic bird confined to three forests in the Taita Hills (in the south east of Kenya): Mbololo, Chawia and Ngangao. The forests cover a tiny 342 ha. BirdLife International, which championed an IUCN red listing of the species says in its fact sheet: “The bird is considered Critically Endangered because it has a tiny occupied range, within which its montane forest habitat has been severely fragmented and continues to decline in both extent and quality”. Conservationists are using birds – with the thrush as the flagship species – to champion the conservation of the Taita Hills forests.
According to a previous study by Edward Waiyaki and others (unpublished) on this thrush, Chawia forest was estimated to have a population of 38 individuals, while Ngangao and Mbololo had 250 and 1,060 individuals respectively. Another analysis based on molecular work by Galbusera and others in 2000 gave effective population size estimates of 3-30 in Chawia, 15-150 in Ngangao and 75-750 in Mbololo. In addition to a genetic bottleneck, Chawia’s population shows what ornithologists call “a highly male-biased sex ratio” – only 10% of birds were found to be female.
Now a team is correcting this imbalance by translocating several individuals of the thrush (predominantly females) from Mbololo, which has a larger population – and even sex ratio – to Chawia. Since 2005 the Critical Ecosystems Partnership Fund (CEPF) has been funding conservation projects in Taita Hills, which involved rehabilitation of the forest by the local communities and the government. Optimism is high that the ongoing reforestation and planned improvements of connectivity with other fragments and populations of the Taita Hills forests will improve Chawia. However, given the current trend, it is unlikely that the thrush subpopulation in Chawia will survive long enough to benefit from these restoration efforts, making this translocation both necessary and timely.
I have also since learnt that the birds are likely to suffer from genetic inbreeding if they don’t have more numbers of mates. Amazing what you can learn from the birds!
The East African Wild Life Society (EAWLS) has been running a Taita Hills Project which is focusing on conservation and management of the Taita forests through community participation.