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Location Kenya, Central Province
Central coordinates 36o 25.62' East  0o 6.48' South
IBA criteria A1, A2, A3
Area 4,600 ha
Altitude 2,340 - 2,400m
Year of IBA assessment 2007


Site description Lake Ol' Bolossat, Central Province's only natural lake, is an internal drainage basin whose swamps have a high salt content possibly due to high evaporation rates and partly to the nature of sediments that constitute the area (Krhoda 1992). The lake is situated in the valley between the northwestern slopes of Aberdares Mountains and Dundori Ridge which are the main catchments. The altitude ranges from 2,340 - 2,400 meters above sea level, receiving an average precipitation of 975 - 1,100 mm pa. The Lake covers an area of 43.3 of which open water covers about 4 This drainage basin, Ewaso Ngiro North Basin covering 210,226, is Kenya's largest. It offers a variety of habitats ranging from open water through floating marsh and swamps, open grasslands and riverine forests along rivers and springs that feed the lake.

Key Biodiversity Lake Ol’ Bolossat holds a wealth of bird species that would attract bird watchers in the tourism industry. A total of 49 species were recorded in a survey by Wamiti et al in 2007. The Lake is known to be important for Palearctic migrant waterbirds. During the 2007 survey, 17 waterbird species that are listed by the African-Eurasian Waterbird Agreement (Ng'weno et al 1999) were recorded. This emphasizes the importance of protecting the wetland for, among other reasons, being close the Great Rift Valley, one of Kenya's important migration flyways, thus offering a suitable site for feeding and resting, and probably as a wintering ground for the Palaearctic migrants. The area around Lake Ol’ Bolossat holds a significant area (c.39 of unique montane grasslands. The highland grasslands of central Kenya contain a suite of restricted-range bird species, forming part of Kenyan Mountains Endemic Bird Area (Stattersfield et al 1998). These grasslands have received virtually no conservation attention from the authorities, are largely unprotected and are vanishing at an alarming rate (Fanshawe & Bennun 1991, Bennun & Njoroge 2001) despite being habitats for globally-threatened bird species as well as other biodiversity. Sharpe's Longclaw Macronyx sharpei, a globally-threatened and Kenyan high-altitude grassland endemic bird (BirdLife International 2000, 2006, Muchai et al 2002, Muchai 1997), has been recorded in the area’s open grasslands during a waterfowl census (Mungai & Manegene 1998) and in early 2007. Suitable habitat for Sharpe's Longclaw in Kenya is found in Kinangop, Mau Narok & Molo grasslands, and Uasin Gishu plateau. Previous records reports this species as having been recorded from the north-west slopes of Mt. Kenya and the moorlands of Aberdares Mountains although there have been no recent records in these two sites (Zimmerman et al 1996). The presence of Sharpe's Longclaw has been confirmed at Lake Ol' Bolossat, which extends the species' current known distribution and further suggests that it might have had a wider distribution than historically known. Jackson's Widowbird Euplectes jacksoni, also a restricted-range species and described as near-threatened (NT) by BirdLife International (2000), was also recorded in private farms. There has been scarce and unpublished information on sightings and status of these two species, or that of their grassland habitat at the site. Long-tailed Widowbird E. progne, a regionally-threatened species, was also observed. Hunter's Cisticola Cisticola hunteri (Least Concern) was recorded mainly from bushes in the farmlands. The Lake's open water and swamps are home to a number of waterbirds. Interesting species observed includes African Marsh Harrier, Purple Swamphen, Black-bellied Bustard and Capped Wheatear. The most abundant species recorded in the 2007 survey were Long-tailed Widowbird (114), Red-capped Lark (93) and Grassland Pipit (89).

Non-bird biodiversity: Hippopotamuses, estimated at over 200 individuals, which graze overnight.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Jackson's Widowbird Euplectes jacksoni resident  2007  < 50 individuals  good  A2, A3  Near Threatened 
Sharpe's Longclaw Macronyx sharpei resident  2007  < 50 individuals  good  A1, A2, A3  Endangered 

IBA Monitoring

2013 high unfavourable low

Agriculture and aquaculture livestock farming and ranching (includes forest grazing) - small-holder grazing, ranching or farming happening now some of area/population (10-49%) slow but significant deterioration medium
Biological resource use hunting & collecting terrestrial animals - intentional use (species being assessed is the target) happening now some of area/population (10-49%) slow but significant deterioration medium
Climate change and severe weather drought happening now whole area/population (>90%) slow but significant deterioration high
Climate change and severe weather storms and floods happening now small area/few individuals (<10%) slow but significant deterioration low
Human intrusions and disturbance work and other activities happening now majority/most of area/population (50-90%) moderate to rapid deterioration high
Invasive & other problematic species, genes & diseases invasive non-native/alien species/diseases - named species happening now some of area/population (10-49%) slow but significant deterioration medium
Pollution garbage & solid waste happening now small area/few individuals (<10%) no or imperceptible deterioration low
Residential and commercial development housing and urban areas happening now some of area/population (10-49%) slow but significant deterioration medium

Grassland   0 0 moderate (70-90%) moderate (70-90%) unfavourable

Some of site covered (10-49%)  A management plan exists but it is out of date or not comprehensive  Some limited conservation initiatives are in place  low 

Local conservation groups The local conservation group below is working to support conservation at this IBA.

Name Year formed
Nyahururu Bird Club 2008


IUCN habitat Habitat detail Extent (% of site)
Wetlands (inland) Freshwater lakes and pools  9%
Grassland Grassland - montane  91%

Land ownership  Unprotected.

Land use

Land-use Extent (% of site)
agriculture 70%
Notes: Small and large-scale intensive agriculture.
other 5%
Notes: Quarrying
forestry 1%
Notes: Farm woodlots
nature conservation and research 15%
Notes: Wildlife conservation

Acknowledgements The British Ornithologists’ Union (BOU) for providing funds for research. The Wetlands Programme and Office of the Deputy Director Biodiversity Research & Monitoring at Kenya Wildlife Service headquarters. The Chairman, Lake Ol Bolossat Conservation Network, Mr. Joseph Mbugua, for logistics. Field assistants and community local guides Teresia Maina and Paul Ndegwa, and Catherine Wambui of Kenya Forest Service based at South Marmanet Forest, for their field work facilitation

References Survey of globally-threatened birds at Lake Ol Bolossat Grasslands, central Kenya by Wanyoike Wamiti,Philista Malaki & Andrew Mwangi.Research Reports of the Directorate of Research & Collections, National Museums of Kenya: Ornithology, 78 (2007)

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Lake Ol' Bolossat. Downloaded from on 28/10/2016

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