Sites - Important Bird Areas (IBAs)

Ornithological information The number of birds present at this site is largely dependent on rainfall and on the quantity of river water allowed in through the dykes. Other counts have included 1,800 Limosa limosa and 410 Plectropterus gambensis in 1987, while in November 1999 an aerial survey recorded 43,600 waterbirds.

Site description Rkîz is situated approximately 90 km north-east of the town of Rosso. It is a depression 34 km long and 4–6 km wide aligned north-east–south-west. It is filled by water from the Senegal river and, to a lesser extent, from run-off due to rainfall. Two swamps, the Nasio and the Laouwaya, join Rkîz to the river system. The eastern part of the lake is 3 m below sea-level and the western 2 m below. The lake has dried out completely in drought years. The construction of a dam in the Laouwaya, as well as a dyke at Nasio, has limited the natural filling of the lake and reduced the area of the lake to 6,100 ha. The whole area is now managed by a system of dams and dykes for the cultivation of rice.

The transformation of the lake into an agricultural zone has led to the loss of most of the original vegetation. The northern part of the lake remains the most species-rich. It is dominated by Cassia tora, with Nymphaea sp., Mimosa pigra, Indigofera oblongifolia, Echinochloa pyramidalis and Aeschynomene sp. The banks are typically covered with grasses such as Cynodon dactylon, Dactyloctenium and Eragrostis spp. Elsewhere, remaining trees include Acacia raddiana and A. senegal as well as Leptadenia pyrotechnica. Following clearance for agriculture Calotropis procera has colonized much of the area and is now the dominant ligneous species. In the south-west there are some saline soils with Tamarix senegalensis. In the south-east, where the oueds lead to Nasio and Laouwaya, some stands of Acacia nilotica still persist, due to seasonal flooding via the rice-fields.

Populations of IBA trigger species

Species	Season	Period	Population estimate	Quality of estimate	IBA Criteria	IUCN Category
Northern Pintail Anas acuta	winter	1975	10,000 individuals	-	A4i	Least Concern
Garganey Anas querquedula	winter	1999	27,800 individuals	-	A4i	Least Concern
Purple Swamphen Porphyrio porphyrio	winter	2000	206 individuals	-	A4i	Least Concern
A4iii Species group - waterbirds	winter	-	-	unknown	A4iii

Habitats

IUCN habitat	Habitat detail	Extent (% of site)
Artificial landscapes (terrestrial)		40%
Grassland		59%

Land use

Land-use	Extent (% of site)
agriculture	-
forestry	-
water management	-
other	-
Notes: Firewood collection.

Other biodiversity Crocodylus niloticus and Hippopotamus amphibius are reported to be present in the area; both are nationally threatened.

Management considerations The traditional multi-use management systems, which included flood-recession cultivation of sorghum and livestock-rearing, have been replaced by more intensive agricultural systems. Although levels of rice production at Rkîz are higher than along the Senegal river (1.9 versus 1.5 tonnes/ha/year), this does not compensate for the loss of pastureland and livestock production. In fact, the expansion and intensification of agriculture has been to the detriment of the animal herding in the area. Conflicts between farmers and herders have increased, fishing is seriously affected as water-levels are too low, the water is increasingly polluted by fertilizers and pesticides, while felling of the Acacia nilotica woodland for fuel- and construction-wood and to clear land for agriculture has significantly reduced habitat suitable for tree-roosting species such as Nycticorax nycticorax. Only a few roosting sites remain today.

References Roux (1976), van Wetten (1989).

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Recommended citation  BirdLife International (2013) Important Bird Areas factsheet: Rkîz. Downloaded from http://www.birdlife.org on 23/05/2013

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