The Chyorny (Black) Irtysh delta makes up an appreciable part of area fringing the eastern shore of Lake Zaisan. The total area can be split notionally into 3 major subdivisions: the southern delta – the water complexes of the Kendyrlyk branch; the central part – the segment of the Chyorny Irtysh proper, with numerous subsiduary channels branching from the main channel; and and north-western delta including the branches of the Stary (Old) Irtysh and Zhankarasu rivers and all intervening areas. All of the channels follow extremely tortuous routes, often re-entering the main waterbody not far from the spot of initial meandering.
The southern delta comprises vast expanses of dense reed alternating with the stretches of open waters. The shoals are covered by mature beds of reed mace (Typha sp.), and every sheltered backwater contains well-developed communities of water-plants including Potamogeton sp., Nuphar lutea, Trapa sp. and Polygonum amphibium. Further east, the typical landscape of the delta gradually gives way to a swampy congregation of alluvial banks eventually becoming boggy terrain with an intricate system of sandy islands separated by waterlogged areas and marshes. The archipelago-like component of this wetland area is actually the upper part of the deluged portion of the sandy ridges and dunes of the neighbouring desert. The islands are frequently fringed by a mixed border of reed, cattail and scarce willow beds. The line of the Kenderlyk branch consists of innumerable branches, many often terminating in clogged impasses, and frequently changing their courses as the result of flooding. Upstream of the delta, a distinct shoreline only appears in the middle section of the Kendyrlyk channel, with scattered patches of trees gradually turning into small groves of Salix and Populus at the further reaches of delta.
The central part of the delta is bisected by the main stream of the Chyorny Irtysh which also consists of an intricate complex of open water channels. This section of the area supports frequent stands of riverine Populus-Salix groves. In the upper reaches tree growth is substantial forming a dense forest with an underlying maze of half-overgrown channels with water-logged banks. Beneath the trees there are prolific growths of tall meadow grasses or feeble reeds. The understoey is mainly Halimodendron argenteum and Rosa sp. The banks of the main stream have the appearance of a low cliff (1-1.5 m high) of sand-clay subject to continuous erosion. Owing to its tortuous nature the main course is full of spits, shoals and bays with placid water.
The north-western part of the delta is made up by a network of two major branches - the Old Irtysh and Zhankarasu. These areas are slightly higher than the rest of the area which means that the highest areas often excape regular seasonal flooding. There are lush grass and herb flood meadows fringed, in most areas, by forest belts. Such areas are the main moulting areas of geese (Anser anser).
These parts of the site are subject to the major impacts of human industrial activities. The rustic and agricultural interests of the Markakol district population are concentrated on the cattle raising industry. Therefore, a significant portion of the north-western delta, with the most promising herbage, is used extensively for cattle raising, dairy farming and extensive hay mowing. Annually, considerable areas of dead reed are burnt to create additional winter grazing. The flood-forest areas are often subject to wood cutting and much of the area is now crossed by roads and tracks.
The final part of the delta is where the system of Chyorny Irtysh naturally ends in Lake Zaisan. Here there are huge patches of tall reed that are often submerged when laid flat by the strong and frequent easterly winds driving across the expanse of the lake. This area is generally avoided by any large number of birds.
Between 29 June and 6 July 2006 within the boundaries of the Chyorny Irtysh delta, direct observation recorded more than 10,000 birds of 110 species. The highest species’ diversity and numbers (8,443 birds of 88 species) were observed in the southern part of the delta in the complex of waterbodies and land on the Kenderlyk Branch. The count includes 3,000 Phalacrocorax carbo, 1,000 Pelecanus crispus and 3,000 Riparia diluta. The single, well-established huge colony of Pelecaniformes lies within the former Krivoye lake (47°44'13,7"N, 84°36'05,9"E). On June 29 2006, inspection of the colony revealed 300 nests of Pelecanus crispus and about 700 nests of Phalacrocorax carbo. In the nearby cluster of islets there were 400 fledglings of Pelecanus crispus and a few nests of Phalacrocorax carbo. Rare species occurring at the site include Haliaeetus albicilla, Pelecanus onocrotalus, Cygnus cygnus and Grus virgo. Two Platalea leucorodia and 3 Cygnopsis cygnoides were reported to have been seen in the previous spring (personal report of A.I. Karamyshev).
In the central part of the site 1,074 birds of 77 species were recorded. As the habitat is very different here, with woody forming a substantial part, the species recorded were quite different: Nycticorax nycticorax, Anser anser, Bucephala clangula, Mergus merganser, Pandion haliaetus, Haliaeetus albicilla, Pelecanus onocrotalus, P. crispus and Cygnus cygnus, the last five species being included in the National Red Data Book.
The north-western part of the site, with the major branches of the Zhankarasu, Old Irtysh and the main part of the north-south sprawling delta supports fewer birds - only 554 individuals of 43 species. However, this area was found to support a roosting party of 33 Larus ichthyaetus.
Non-bird biodiversity: In Lake Zaisan and the low reaches of the Chyorny Irtysh there are modest populations of rare fish included in the Red Data Book of Kazakhstan: Inconny (Stenodus leucichthys nelma) and Taimn trout (Hucho taimen P.). Sus scrofa is very common in the thickets of the delta. In all of the higher areas adjacent to the delta there are substantial numbers of Ellow lemming (Lagurus luteus E.), which constitutes an important food component in the diet of local avian and mammal predators. Nationally protected species also occur.
Pressure/threats to key biodiversity
The natural landscapes of the entire complex are suffering from regular burning of the reedbeds. The fires often get out of control and spread throughout large parts of the delta. In some years the fires smolder through the summer and trigger fires in autumn. Apart from the immediate threat to breeding bird populations, a secondary impact is that when core stands of reed growing in the deep water stretches of the estuary are damaged, wave action can destroy or frangment unburnt reed stand, further reducing nesting opportunities.
Since Mustela vison, a common, feral, alien species introduced to the area approximately 10 years ago, the population of muskrat (Ondatra zibethica) has dwindled remarkably. Fulica atra populations also look to be affected dramatically: between 29 June and 6 July 2006 not a single bird was observed.
The landscapes and fauna of the delta are subject to the negative effects of accidental alterations of the water level regime in Lake Zaisan linked to level regulations essential for the proper functioning of the Bukhtarma Electric Power Plant. Drastic surges of water result in the mass loss of shore- and waterbird nests.
Conservation responses/actions for key biodiversity
The composition and numbers of the Chyorny Irtysh bird populations deserve further, thorough scientific clarification, especially as the site lies on a major migration flyway and has a rich diversity of habitats. Future research of the shore- and waterbird seasonal migration should be a priority for national ornithological teams (preferably in late April/early May, and September) conducted, whenever possible with monitoring of nesting birds.
Habitat and land use
The southern part of the delta is least exploited as few locations are accessible by vehicles other than boats. Formerly the area was used by reed-mat makers but these activities gradually died out about 15 yeas ago.
BirdLife International (2021) Important Bird Areas factsheet: Cherniy (Black) Irtysh Delta. Downloaded from
http://www.birdlife.org on 22/01/2021.