Sorbalyk and Maibalyk lakes are the major elements of the IBA which also includes seven, similar, waterbodies. The complex, in turn, is a fragment of the expansive lake country occupying the entire outer edge of the southern West-Siberian Lowlands. The lakes lie on the left bank of the middle reaches of the Ishym river. Administratively the site is located in the western corner of the Northern Kazakhstan region, very close to the interregional border, and 200 km to the west of the regional centre of Petropavlovsk, 40 km to the south of Presnovka and 20 km to the south-west of Blagoveschenka. On the eastern side of Maibalyk lake there is a village of the same name.
The major land form and vegetation is forest-steppe, though the typical forest stands of this vegetation zone are restricted to the north-western part of the area. During the period of agricultural expansion, about half a century ago, more than half of the virgin mesophylic steppe of the region was ploughed and converted to cultivation. Nowadays, about 55% of the area around the lake are crop fields. Set in a shallow depression Maibalyk Lake is a waterbody of irregular circular shape 1.7 km in length and 1.3 km in width. It lies among a scattering of similar small waterbodies, each averaging 50-60 ha in area. In total, the wetland complex of the Ubagan-Ishym Confluence occupies 4.0-4.5% of the total area of the territory.
The land around Sorbalyk Lake was not converted to agriculture as the soil is very saline. Arable fields never approach the shore closer than 150 m. Steppe occurs at the southern end of the lake, within 1 km of the shore, while in the north, a few stands of birch forest approach to within 150-200 m of the shore. This portion of the area has a rather low human population. The lake consists of two waterbodies usually connected by a natural channel. In years when the hydrological cycle is low, the lake forms two separate waterbodies.
About 60 waterbird species have been recorded and the lakes are considered to be an important place for migratory waterbirds. Despite being in the proximity of areas of high population, many thousands of passage waterbirds were recorded using Maibalyk lake about 10-15 years ago. In the late 1980s and early 1990s, spring counts recorded 3-4,000 Anser albifrons and 200-300 Branta ruficollis. Throughout the entire migration period, 20-25,000 waterfowl were estimated to use this waterbody. However, more recent monitoring (2003-2007), indicates that conditions at the lake are deteriorating and bird numbers declining. Nevertheless, the lake is continuing to provide a resting and feeding area for the large numbers of waterbirds that migrate through the region annually. Passage raptors include Aquila chrysaetos and Haliaeetus albicilla.
The comparatively large size of Sorbalyk lake provides a safe refuge and the proximity of cereal fields provides good feeding for many species of ducks, geese and Cranes. The low human population means that there is little disturbance.
Non-bird biodiversity: The mammal fauna appears to be scanty. Murine rodents are the most prolific and include Apodemus agrarius and Microtus arvalis and, in the wet habitats, Ondatra zibethica and Arvicola terrestris. In the intact areas of steppe Marmota bobac can be found in good numbers. Other commonly encountered species are Erinaceus europaeus, Vulpes vulpes, Lepus timidus, Lepus europaeus and Mustela eversmanni.
The dominant component of the emergent vegetation is Phragmites australis. In some areas it occurs together with Typha angustifolia and Scirpus lacustris, while the muddy shoals are dominated in many places by Carex sp. A few patches of steppe still survive but are severely degraded, though still support remnants of the rich-herbage-motley-turf-grass associations.
Pressure/threats to key biodiversity
Declining bird numbers recorded for the eastern part of the lake complex are directly related to Man-induced deterioration of the habitat and increasing disturbance. Fishing on Maibalyk lake has become intensified and there is overgrazing at some parts of the site. Traffic causes noise pollution. Spring flooding can result in pollution from manure-laden effluents. The lake's shores often attract roving packs of dogs. Frequent stubble burning can also prevent migrating birds from landing on the lake. There is also pressure from hunting, even in spring when goose hunting is forbidden. The area surrounding Sorbalyk lake is suffering from mild overgrazing/trampling by cattle. It is expected that intensive crop production will increase in this part of the site, with the associated hazards of chemical application, including the aerial spraying of fields with herbicides.
Habitat and land use
In the light of the current economic climate, the area can be considered to be well-developed. Cultivation constitutes 55% of the entire district and the mean population density is 8 people per square kilometre. Settlements are separated by an average distance of 16-20 km and the total resident population is 1-2,000 people. Small-holder cattle-raising is also gradually increasing. On the land immediately bordering Maibalyk lake, crops only occupy a minimal area with the bulk being used for livestock raising and there is serious over-grazing. The fish-rich waters of the lake attract a large number of amateur fishermen. The lake is also surrounded by roads and traffic can cause disturbance.
About 10% of the terrestrial part of the western half of the site is arable and the rest pasture and, at present, pressure is low. However, it is expected that regional livestock numbers will increase in the future, possibly to the levels of the late 1980s, and this may cause localised problems. There are restrictions on hunting in the vicinity of the lake but occasional illegal hunting does take place causing disturbance.
BirdLife International (2020) Important Bird Areas factsheet: Sorbalyk-Maybalyk Lake System. Downloaded from
http://www.birdlife.org on 20/09/2020.