An international team of ornithologists has described and named two new species of the warbler genus Cisticola using museum specimens collected half a century ago in Tanzania.
New species of Cisticola warblers from the Kilombero floodplain of Tanzania: at the top, Kilombero cisticola; at the bottom white-tailed cisticola; for both species, the bird in the front is painted after the type specimen while the bird behind is based on photos of birds in more worn plumages. Image credit: Jon Fjeldså.
Cisticola is a genus of small insect-eating birds in the Old World passerine family Cisticolidae.
Established by the German naturalist Johann Jakob Kaup in 1829, it contains over 50 recognized species.
Of these species, only two are found outside of Africa: one in Madagascar and the other from Asia to Australasia.
“Cisticola warblers primarily inhabit wetlands, savannah, broadleaved woodlands and upland habitats, almost exclusively in Africa,” said University of Copenhagen researcher Lars Dinesen and his colleagues from Denmark, Sweden, South Africa and the United States.
“Their identification and classification have been problematic for both professional and amateur ornithologists because of their cryptic coloration, seasonal variation in plumage and the patchy geographical distributions of many of the currently recognized species.”
The two new Cisticola species are endemic to the marshes of the Kilombero floodplain of southwestern Tanzania.
“The presence of two undescribed Cisticola warblers in the marshes of the Kilombero floodplain in central Tanzania has been known since the 1980s and these putative new species have been illustrated in field guides on African birds, although with no formal name,” the researchers explained.
“Based on the combined evidence from genetics, morphology and bioacoustics, we conclude that these two cisticolas represent independent species.”
One of the two new species, named the Kilombero cisticola (Cisticola bakerorum), is distributed in lowland marshes at elevations between 240 and 305 m.
It prefers flooded reedbeds and is common along the Kilombero River and the other major river channels of the Kilombero floodplain.
The second species, the white-tailed cisticola (Cisticola anderseni), is known from the Kilombero floodplain south of the rural town of Ifakara in southern central Tanzania.
Both species became isolated and diverged from their sister-species between 2.5 and 3.5 million years ago.
“The Kilombero floodplain was once connected with the vast wetland habitats of the ancient Zambian Luangwa drainage system,” the scientists said.
“However, this connection was broken in the Late Miocene, with the formation of the Malawi Rift.”
“Our genetic data suggest that the cisticolas of the Kilombero floodplain are evolutionarily much too young to have been part of the fauna of this ancient wetland system, and more probably they colonized the area from the adjacent highlands or from the neighboring coastal plains.”
The authors propose that both species should be classified as Globally Endangered, owing to immense anthropogenic pressures to the floodplain.
“The fieldwork suggests that the Kilombero cisticola is quite narrowly associated with water and flooded marsh with tall reeds and sedges along the major river channels, with a preference for tall Phragmithes mauritianus,” they said.
“Whereas the white-tailed cisticola prefers shorter or more open vegetation with patches of drier habitat, where it feeds by walking on sandy ground.”
“While this difference in habitat use may make the two Cisticola species differently affected by the intensive recent land-use, we propose to classify both species as Endangered (following criteria of IUCN 2019) due to an inferred population size reduction as a result of an alarming decrease in habitat quality.”
A paper describing the discovery was published in the journal Ibis.
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Jon Fjeldså et al. Description of two new Cisticola species endemic to the marshes of the Kilombero floodplain of southwestern Tanzania. Ibis, published online May 17, 2021; doi: 10.1111/ibi.12971
