Bolshoi Kak lake lies at the western edge of a group of widely separated waterbodies on the left bank of the upper middle reaches of the Ishym river valley. Administratively the site is located in the western corner of the Northern Kazakhstan region, very close to the interregional border. The lake is situated 280 km south-west of the regional centre of Petropavlovsk and 30 km south-west of the district centre of Timiryazevo. 25 kms from the eastern boundary of the site there is a railway running north-south.
The site occupies a small part of the southern outer range of the West-Siberian Lowlands. The major type of land form and vegetation is forest-steppe, though within the site itself isolated forest stands are absent. More than half of the surrounding mesophylic steppe was converted to agriculture about half a century ago and now about 80-85% of the area are crop fields. Bolshoi Kak lake is a rather shallow waterbody of irregular oval form, stretching 9.3 km in length and 7.3 km in width, set in a shallow hollow. The lake is dependent on the intake of seasonal melt-water floods and, along with several associated waterbodies in the region, is subject to cyclic filling-up. The banks are void of any significant quantities of emergent vegetation. The central part of the lake, with a maximum depth of only about 1 m, is surrounded by a broad zone of muddy shoals. In years when water levels are low, the lake reduces in size by 20-40%.
Large numbers of waterfowl and shorebirds occur in both autumn and spring. In some years, for example 1995, 1997, 2000 and 2005, even in spring, one time aggregations of waterfowl totalled 20-25,000 birds. Whilst it is difficult to determine accurately individual species totals, the cumulative appraisal of several years data suggests the following annual numbers: Anser albifrons 25-30,000, Branta ruficollis 5-7,000, Cygnus cygnus up to 3,000. On passage, especially in autumn, there also occur impressive concentrations of Grus grus – 1.5-2,000 birds. Similarly, five Haliaeetus albicilla were recorded on 20.10.2007. Passage wader numbers are also high, for example in late May 2003, at one random vantage point 133 Numenius arquata were counted. Himantopus himantopus and Recurvirostra avosetta appear to be very common.
In summer the lake supports breeding surface-feeding ducks. In mid-summer the site is known to be frequently visited by non-breeding flocks of Cygnus cygnus and Cygnus olor. Anser anser numbers begin to increase from the end of July.
Non-bird biodiversity: Of mammals several species of mustelid occur - Mustela nivalis, Mustela erminea, Mustela eversmanni, Meles meles and Mustela sibirica. Larger predators include Canis lupus, Vulpes vulpes, and more rarely encountered, Vulpes corsac and Nyctereutes procyonoides. Bordering the lake are a few areas of slightly modified steppic landscape still featuring an assortment of rich-herbage-motley-turf-grass associations.
Habitat and land use
The major impact of man-made activities is the increasing use of surrounding areas for the production of cereal crops, particularly wheat. For the bird populations the transformation of the adjacent steppe works two ways: the birds have become accustomed to using the additional forage available in the form of scattered grain; on the other hand, frequent stubble burning has a negative effect on nesting and resting. Often such fires last from several days to 1-2 weeks, influencing first, the option and, second, the duration of the birds’ stay. In the last 5-7 years this hazard has shown a tendency to increase. Intensive chemical treatment of crops also takes place and its effects of the water quality of the lake is unknown. The remaining land area is used for cattle grazing, which is expected to intensify as livestock numbers increase. Even today, the grazing-related degradation of the habitats closest to shore is noticable.
Pressure/threats to key biodiversity
Threats are linked to the character and scope of habitat exploitation.
1. Disturbance during the periods of spring and autumn agricultural activities - harvesting, ploughing, fires.
2. Gradual increases in both legal hunting and poaching in the locality may, eventually, lead to their expansion from the traditional inland-situated shooting areas to the shore zone, or even onto the lake itself. More often than not, the effect of this particular hazard is ignored by the protection agencies and stays disregarded until it occurs in organised groups of 15-20 sportsmen using automatic weapons.
3. The drastic transformation of terrestrial habitats as the result of intensive grazing and disturbance.
Conservation responses/actions for key biodiversity
On 12.06.2003 the lake was visited and explored by two British ornithologists - Gordon Allison and Adam Rowlands (E-mail: email@example.com). No other external research is known.