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Location Kenya, Coast Province
Central coordinates 40o 20.00' East  2o 30.00' South
IBA criteria A1, A3, A4i, A4iii
Area 130,000 ha
Altitude 0 - 37m
Year of IBA assessment 2001

NatureKenya



Site description The Tana delta is the name loosely given to the flood-plain ecosystem of the lower Tana river, a vast wetland complex on the Kenyan coast. The delta is roughly triangular in shape, with its apex at Lake Bilisa (north of Garsen) and its base a 50 km stretch of beach along Ungwana (or Formosa) Bay, stretching from Kipini in the north-east to Mto Kilifi in the south-west. This low-lying area is bounded by higher land to the east and west, and to the south by a dune system bordering the Indian Ocean. It forms the interface between the river and the ocean, with fresh and brackish lakes and streams, freshwater and saline grasslands and wetlands, and successional stages of forest and woodland on the riverbanks and the dune ridges parallel to the shore. The mouth of the river has shifted many times. Today, the main stream of the Tana follows an artificial course, directly into an estuary at Kipini, rather than into the complex system of channels and distributaries leading to its old mouth at Mto Tana. Until recently, some fresh water still flowed into the ‘old’ delta through one of these channels, the Kalota Brook. However, since 1988 a small dam has blocked this, built by Pokomo farmers, who use the tidal bore to push fresh water into their fields and irrigate their crops. Alluvial sediments cover the entire flood-plain in the lower parts. Flooding happens as a result of rain in the river’s catchment on Mount Kenya (IBA KE005) and the Aberdare mountains (KE001). Normally, the major floods occur in April–May, with a smaller, short-rains flooding in October–November. The timing, extent and duration of the flooding vary greatly from year to year. The Tana river delta contains a very wide variety of habitats, including riverine forest, grassland, woodland, bushland, lakes, mangroves, dunes, beaches, estuaries and coastal waters. Small fragments of riverine forest, not nearly as extensive as the forests north of Garsen (see KE023), occur along the present or former river courses. Seasonally flooded flood-plain grasslands cover c.67,000 ha of the delta. West of the flood-plain is a diverse bushland. Wooded bushland or grassland, with fire-resistant tree species, occupies a broad swathe east of the flood-plain, merging into the Boni forest vegetation to the north. Other bushland associations form a complex mosaic with the flood-plain grasslands. Parallel to the coast along Ungwana Bay run lines of high dunes, some as much as 37 m above the sea. These are covered by their own distinctive vegetation, a dense thicket dominated by Dombeya sp. and Grewia similis. In the valleys the thicket mingles with taller trees, including various palms. Palms are prominent in many places. In some areas, especially those cleared and burned in the past, these form substantial tracts of palm-bushed grassland. Tall mangrove forest grows at Kipini in the Tana estuary and along the network of channels further south. As well as seasonal wetlands in the oxbows and flood-plain depressions, the delta contains a number of near-permanent lakes and marshes. Some of these may dry out in certain years, but others, like Lake Shakababo and Bilisa, maintain true aquatic plants and good populations of several species of fish. Luo and Luhya immigrants to the area are responsible for an active and thriving fishery, while Orma pastoralists use the wetlands as dry-season grazing areas for their livestock. Fishermen also camp for days or weeks, while catching, salting and drying fish, on the coral outcrops of Mwamba Ziwayuu, c.10 km offshore from Kipini. The other main ethnic group in the area, the Pokomo, are agriculturalists who cultivate a narrow strip on either side of the river, and around the seasonal and permanent wetlands. As the floods start to recede, rice is planted in the shallow water. Several crops of rice follow the water as its level drops, and other crops, such as maize and sweet potatoes, are planted on the drying mud. There is also an irrigation scheme growing rice in traditional style at Ozi, near Kipini, and a much larger, mechanized one upstream, east of Garsen, that is eventually intended to cover as much as 16,000 ha.

Key Biodiversity See Box and Table 3 for key species. The Tana river delta is a stronghold for two Near Threatened, restricted-range species, Anthus melindae and Acrocephalus griseldis (probably its main wintering ground). Circaetus fasciolatus is uncommon in riverine forest, but has not been recorded in recent surveys. The wetlands, including the coastline and offshore islets, at times hold exceptional concentrations of waterbirds. Internationally important populations have been recorded here for no fewer than 22 species, making the delta one of the key sites in the country for waterbird conservation. The Tana delta also supports one of the very few breeding sites for colonial waterbirds in Kenya. This heronry is near Idsowe, south of Garsen, on Ziwa la Matomba, a seasonally-flooded lagoon where the birds nest in a thicket of Terminalia brevipes, usually between May and September but also at other times if the lagoon is flooded. Up to 5,000 colonial waterbirds of at least 13 species have been recorded nesting here, including Anhinga rufa (up to 100 pairs), Ardea cinerea, A. purpurea, Egretta ardesiaca, Ardeola ralloides and Nycticorax nycticorax, Casmerodius albus, Mesophoyx intermedia and Egretta garzetta, Anastomus lamelligerus, Threskiornis aethiopicus and Plegadis falcinellus, and Platalea alba. Mwamba Ziwayuu, a small coral platform offshore from the Tana estuary, is a resting site for significant numbers of Sterna saundersi and S. bengalensis that feed in Ungwana Bay. Regionally threatened species include Casmerodius albus; Ephippiorhynchus senegalensis (a regular visitor in small numbers, May to September) and Turdoides squamulatus (local and uncommon).

Non-bird biodiversity: The importance of the Tana river delta lies in the expanse, intactness, variety and productivity of its habitats. The flood-plain is grazed by a number of ungulates, including the restricted East African coast subspecies of the ungulate Damaliscus lunatus topi, with some 30,000 or so in the area. The rivers and channels support large numbers of Hippopotamus amphibius (estimated at 400–450) and Crocodylus niloticus. Ungwana Bay is one of the few places where Dugong dugon (VU), critically endangered in the region, has been recorded recently. The turtles Chelonia mydas (EN), Eretmochelys imbricata (CR) and Lepidochelys olivacea (EN) nest on the sandy beaches. Twenty-two freshwater fish species are recorded from the lower Tana, including three eels Anguilla spp. and a distinct subspecies of Petrocephalus catastoma. The mangroves provide vitally important spawning and nursery grounds for many species of fish and crustaceans. The extensive mangrove forests include the only significant stands in Kenya of the plant Heriteria littoralis, and two other plant species that are considered threatened Xylocarpus granatum and Bruguiera gymnorrhiza. At least 280 plant taxa are recorded for the delta, and many more undoubtedly occur as there has been no thorough botanical survey; of these, 18 are considered rare in Kenya or globally.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Brown-breasted Barbet Pogonornis melanopterus resident  1999  present  A3  Least Concern 
Spur-winged Goose Plectropterus gambensis winter  1993  5,400 individuals  A4i  Least Concern 
Greater Flamingo Phoenicopterus roseus winter  1993  2,240 individuals  A4i  Least Concern 
Yellow-billed Stork Mycteria ibis winter  1993  970 individuals  A4i  Least Concern 
African Openbill Anastomus lamelligerus winter  1993  3,530 individuals  A4i  Least Concern 
African Spoonbill Platalea alba winter  1993  3,680 individuals  A4i  Least Concern 
Cattle Egret Bubulcus ibis winter  1993  11,270 individuals  A4i  Least Concern 
Mesophoyx intermedia winter  1993  2,000 individuals  A4i  Not Recognised 
Great White Egret Ardea alba winter  1993  2,560 individuals  A4i  Least Concern 
Great White Pelican Pelecanus onocrotalus winter  1993  2,070 individuals  A4i  Least Concern 
Pink-backed Pelican Pelecanus rufescens winter  1993  2,500 individuals  A4i  Least Concern 
Southern Banded Snake-eagle Circaetus fasciolatus resident  1999  present  A1, A3  Near Threatened 
White-fronted Plover Charadrius marginatus winter  1993  1,070 individuals  A4i  Least Concern 
Lesser Sandplover Charadrius mongolus winter  1993  2,340 individuals  A4i  Least Concern 
Marsh Sandpiper Tringa stagnatilis winter  1993  1,690 individuals  A4i  Least Concern 
Little Stint Calidris minuta winter  1993  15,310 individuals  A4i  Least Concern 
Curlew Sandpiper Calidris ferruginea winter  1993  12,960 individuals  A4i  Least Concern 
Sterna nilotica winter  1993  1,450 individuals  A4i  Not Recognised 
Sooty Gull Larus hemprichii winter  1993  830 individuals  A4i  Least Concern 
Slender-billed Gull Larus genei winter  1993  490 individuals  A4i  Least Concern 
Caspian Tern Hydroprogne caspia winter  1993  1,340 individuals  A4i  Least Concern 
Lesser Crested Tern Thalasseus bengalensis winter  1993  1,670 individuals  A4i  Least Concern 
Saunders's Tern Sternula saundersi winter  1993  3,610 individuals  A4i  Least Concern 
Whiskered Tern Chlidonias hybrida winter  1993  1,450 individuals  A4i  Least Concern 
Mangrove Kingfisher Halcyon senegaloides resident  1999  present  A3  Least Concern 
Pale Batis Batis soror resident  1999  present  A3  Least Concern 
Four-coloured Bush-shrike Telophorus quadricolor resident  1999  present  A3  Least Concern 
Fischer's Greenbul Phyllastrephus fischeri resident  1999  present  A3  Least Concern 
Basra Reed-warbler Acrocephalus griseldis winter  present  A1  Endangered 
Scaly Babbler Turdoides squamulata resident  1999  present  A3  Least Concern 
Black-bellied Glossy-starling Lamprotornis corruscus resident  1999  present  A3  Least Concern 
Mouse-coloured Sunbird Nectarinia veroxii resident  1999  present  A3  Least Concern 
Violet-breasted Sunbird Nectarinia chalcomelas resident  1999  present  A3  Least Concern 
Zanzibar Bishop Euplectes nigroventris resident  1999  present  A3  Least Concern 
Malindi Pipit Anthus melindae resident  1999  present  A1, A3  Least Concern 
A4iii Species group - waterbirds winter  1993  100,000-499,999 individuals  unknown  A4iii   

IBA Monitoring

2013 high unfavourable low
Habitat
Unknown

Agricultural expansion and intensification livestock farming and ranching (includes forest grazing) - nomadic grazing happening now some of area/population (10-49%) moderate to rapid deterioration high
Climate change and severe weather drought likely in short term (within 4 years) small area/few individuals (<10%) slow but significant deterioration low
Climate change and severe weather storms and floods happening now some of area/population (10-49%) slow but significant deterioration medium
Energy production and mining oil and gas drilling likely in short term (within 4 years) some of area/population (10-49%) moderate to rapid deterioration medium
Residential and commercial development commercial and industrial development likely in short term (within 4 years) some of area/population (10-49%) slow but significant deterioration medium
Residential and commercial development housing and urban areas happening now small area/few individuals (<10%) slow but significant deterioration low
Transportation and service corridors roads and railroads likely in short term (within 4 years) some of area/population (10-49%) slow but significant deterioration medium

Wetlands (inland)   0 0 moderate (70-90%) moderate (70-90%) unfavourable

Little/none of site covered (<10%)  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
Tana Delta Conservation Organization 2009

Habitats

IUCN habitat Habitat detail Extent (% of site)
Forest Lowland forest - riparian  -
Grassland Grassland - edaphic, wet  50%
Wetlands (inland) Freshwater lakes and pools; Riverine floodplains  -

Land use

Land-use Extent (% of site)
agriculture -
fisheries/aquaculture -

References Andrews et al. (1975), Becha (1997), Britton (1974), Butynski (1995), Cheffings (1987), Coastal ASAL Development Project (1991), Coverdale et al. (1983), Ecosystems Ltd. (1985), Ng’weno (1993), Njuguna (1992), (1993), Nkako (1992), North (1959), Opala (1993), Pearson et al. (1978), Robertson and Luke (1993), Survey of Kenya (1984), Wass (1995), Whitehead (1959).

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Recommended citation  BirdLife International (2014) Important Bird Areas factsheet: Tana River Delta. Downloaded from http://www.birdlife.org on 25/11/2014

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