The Volga river delta is one of the most important areas of birds’ accumulation during their seasonal migrations in Eurasia. At the clusters of Astrakhansky Reserve concentration of migrating waterfowl and near-water birds is especially high: Anseriformes (14 species), Limicolae (25), Laridae (7) and Ciconiiformes (11). Total migrations duration is 9 month, from March until November. Besides common spring and autumn transitional pass, within the Reserve as well as over the whole delta birds also shift to summer molting areas and back before the beginning of main autumn pass (Anatinae, Haematopinae). Also are noted early post nesting movements of many species, fore departure transitions of local populations and non-breeding birds, non-periodical migrations of wintering species, etc. Only in June shifts seemingly subside, but do not end. During migration period prevail whooper swan (Cygnus cygnus) and mute swan (Gygnus olor), grey goose (Anser anser), mallard (Anas platyrhynchos), pintail (Anas acuta), European teal (Anas crecca), garganey teal (Anas querquedula), duck (Anas strepera), pochard (Netta rufina), diving ducks (Aythya ferina and A. fuligula), magpie diver (Mergus albellus). In the nesting period are numerous Ciconiiformes, Pelecaniformes and Charadriiformes, especially great white heron (Egretta alba) and common heron (Ardea cinerea), cormorant (Phalacrocorax carbo), black-headed gull (Larus ridibundus), Caspian gull (Larus cachinnans), great black-headed gull (Larus ichthyaetus), whiskered tern (Chlidonias hybridus), white-winged black tern (Chlidonias leocopterus) and black tern (Chlidonias niger). Accumulations of migrating birds at Damchiksky cluster are enormous. This area is located at the southwestern part of the lower Volga delta, where ice cover breaks earlier in spring and freezes later in winter. In March and April near Makarkin Island and at the adjacent waters stay up to 8 000 – 9 000 whooper swans, in October-November, up to 12 000. Local and passing mute swans keep together with them. Many-voiced chorus of whooper swans in the avandelta is the call for mass migrations not only for swans but also for other species of Anseriformes as well. Autumn stops of swans are long. Whooper swans keep at shallow waters of kultuk area until the river totally freezes over. Before the sea level uplift, at the Damchiksky cluster has formed the largest autumn grey geese accumulation in the Volga delta – up to 30 000 birds. Many swans and geese feed with rhizome and drupes of lotus that grows extensively at the Damchiksky cluster of the Reserve. The Reserve is located at one of the largest migration routes of waterfowl and near water bird species nesting at the West Siberian plain, Northern Kazakhstan and other regions and wintering at the vast area of the south of Western Europe, Africa and Southwest Asia. In spring, transitional migrations prevail. Major part of birds stop at the delta for a short time. Birds mostly keep at shallow reed bed areas of the delta. Total number of water birds per season is estimated as 7 million specimens (Krivenko et al., 1998). Bird fauna of the Reserve counts 279 species, of which 99 nest at the Reserve’s area, 155 are met during migrations and wintering and 23 irregularly visit the area (see table). The basis of local bird fauna is made of wetland species nesting on trees or in reed beds, but trophically connected with water reservoirs; over 30 species are forest dwelling birds, only 3 species belong to meadow ecosystems and 3 to synanthropic species. Bird population of the Reserve is distinguished by diversity and large size. Richness of bird fauna is determined by peculiarities of ecological conditions and geographic location. The Reserve’s area is the part of the Wetland of International importance.
The Volga delta is the habitat and temporary dwelling area for a line of rare and disappearing bird species inscribed on the 2006 IUCN Red list (18 species) and into the Russian Federation Red Data Book (42 species). 64 bird species have been inscribed into the Red Data Book of Astrakhansky Region. 27 bird species of the Russian Red Data Book are nesting in the Astrakhansky Reserve, like Dalmatian pelican (Pelecanus crispus) (small colonies at Damchiksky and Obzhorovsky clusters), spoon-bill (Platalea leucorodia), glossy ibis (Plegadis falcinellus), buff-backed heron (Bubulcus ibis) (single nest found at Trekhizbinsky cluster), osprey (Pandion haliaetus) (3-4 pairs), whitetailed eagle (Haliaeetus albicilla) (up to 50-70 pairs on three clusters), saker falcon (Falco cherrug) (formerly one pair was nesting at Damchiksky cluster), little bustard (Tetrax tetrax) (2-3 pairs at Damchiksky cluster), black-winged stilt (Himantopus himantopus) (several pairs at the same cluster). Upon confirmed data, gallinule (Porphyrio porphyrio) is nesting at areas adjacent to Damchiksky cluster. During shifts and migrations are common great black-headed gull (Larus ichthyaetus), little cormorant (Phalacrocorax pygmaeus), lesser white-fronted goose (Anser erythropus), black-winged stilt (Himantopus himantopus), peregrine (Falco peregrinus); rare but regularly are met during migrations red-breasted goose (Rufibrenta ruficollis), golden eagle (Aquila chrysaetos), steppe eagle (Aquila rapax), white crane (Grus leucogeranus), avocet (Recurvirostra avosetta), Norfolk plover (Burhinus oedicnemus), great bustard (Otis tarda), European white peare visiting species; encounters of Bewick’s swan (Cygnus bewickii), marbled duck (Anas angustirostris) and white-headed duck (Oxyura leucocephala) are possible although they haven’t been met for a long time. In the above water part of the delta dwell forest birds. Among them are common willow nesting species: great tit (Parus major), blue tit (Parus caeruleus), starling (Sturnus vulgaris), oriole (Oriolus oriolus), crow (Corvus cornix), magpie (Pica pica), tree sparrow (Passer montanus), penduline tit (Remis pendulinus); numerous are Cetti’s Warbler (Cettia cetti), ring-dove (Columba palumbus), greater spotted woodpecker (Dendrocopos major), white-tailed eagle, hobby (Falco subbuteo); near the northern boundary of the Damchiksky cluster are met rook (Corvus frugilegus) and red-footed falcon (Falco vespertinus). In osierbeds and the neighboring reeds dwell pheasants (Phasianus colchicus). After high floods and severe winters, the number of pheasants decreases but then their population usually recovers. In the spring and summer period at 1 000 ha of the preserved lands dwell only 50 male specimens, and in autumn on all three clusters – in total about 2 000 pheasants. For reed and cattail associations is typical reed bunting (Emberiza schoeniclus), bearded tit (Panurus biarmicus), great reed warbler (Acrocephalus arundinaceus) and marsh warbler (Acrocephalus palustris), Savi’s warbler (Locustella luscinioides) and sedge warbler (Acrocephalus schoenobaenus). Some species dwell in very diverse lands, like the numerous crows, which, beside the osier-beds, have inhabited reeds in the kultuk zone and the avandelta (in the last decade). In the mass nesting areas of water birds and colonial species crow has become an active depredator long time ago, therefore its population is being regulated at the Reserve. Between northern and southern boundary of the Reserve cuckoo (Cuculus canorus) is met often, especially at the Obzhorovsky cluster (up to 10 specimens per 10 km of the route). It lays eggs generally into warblers’ nests. Willow associations occupy small areas near the northern boundary of the preserved clusters, that is why bird species peculiar to osier-beds are few in number. These are rarely nesting little bustard, quail (Coturnix coturnix) and blackcap (Saxicola torquata). In winter water reservoirs of the Reserve usually freeze. At few ice-holes and the avandelta may winter swan, smew, merganser and tufted duck. The number of white-tailed eagles increases due to shifts from other regions. In warm summers some duck, heron and perching bird species remain at the Reserve. The most numerous are water and near-water birds: swans, geese, river and diving ducks, cormorants, herons, gulls and terns. The most numerous duck species, mallard and pintail, start migration in early March, mass migrations fall on mid and late March. Such widespread species like European teal, tufted duck and golden-eye pass in late March and early April Of geese, the main migrant is grey goose, generally of local population, which appears in the Volga delta among the first arriving species. Whooper swan is transit specie, numerously passing by among the first coming species. Migrations of mute swan are noted starting from mid March. Mute swans are mostly presented by local birds and the significant number of specimens nesting and casting feathers in Kazakhstan. Of other groups is noted the pass of black-headed gull and some northern species of Limicolae genus. In autumn, transit migrations of many species are poorly expressed, except whooper swan, and partly, white-fronted goose (Anser albifrons). Total number of migrant birds in different years is estimated from 5 to 10 million specimens. Last years, due to increasing of depths, the role of the Volga delta as stopover area for migrating water birds has significantly decreased. Upon aircraft counts, the number of migrating Anseriformes in the avandelta of the Volga has last years made up to 3 million specimens, including 160-190 thousands of swans and over 2 million of diving ducks. Species composition of water birds coincides with the spring one. Significant increase of migrating birds is noted in early October. Mass flight falls on late October and November.
Anseriformes are the most diverse in species and most numerous in the wetland species group. Many mute swans, grey geese, mallards and pochards are nesting. Mute swan demonstrates the positive influence of the Reserve to its population in the Volga delta. Restoration of the mute swan population has first begun at the Reserve’s territory. The first nest was found at Obzhorovsky cluster in 1938. In late 1940-s nesting has become regular, and in 1953 15 pairs have been noted here. At the Trekhizbinsky cluster first swans’ nests have been discovered in 1952, at Damchiksky cluster, in 1953. Mute swans began settling outside the Reserve’s area, especially on lands near Obzhorovsky cluster. In 1961 at Obzhorovsky cluster 215 pairs were nesting, 162 of which were situated in groups by 5-7 nests, and one group even counted 30 nests. The total number of the delta population has reached 755 pairs in 1963. In 1967, the swan population size has reached its maximum of 327 pairs, and then started reducing as birds settled the adjacent areas. In 1981-1984 at Damchiksky clusters nested from 270 to 400 pairs, at Trekhizbinsky, from 4 to 11 pairs, at Obzhorovsky, from 250 to 350 mute swan pairs. The total number of pairs within the whole delta made 4-5 thousand pairs. In early 1990-s, due to the water level rise, the number of nesting pairs sharply decreased. At present time the number of nesting pairs has stabilized. In conditions of changing hydrological regime, the mute swan is the most ecologically flexible specie. Before the establishment of the Reserve, there was still a rather high delta grey goose population. After the organization of the Reserve and taking other measures for the bird fauna protection the number of grey geese has significantly increased. In mid 1920-s at the Reserve’s clusters geese nested “in immense quantities”. The population decrease has started in 1984 and kept almost unchanged until the beginning of the current century. The common coot (Fulica atra) dwells at all wetlands but is especially numerous in the kultuk zone and the avandelta, where it nests in reed beds and bur-reed beds (was nesting formerly before the water level rise). In late summer flocks of 1500-2000 mature and young coots shift along shallow areas near avandelta islands; in autumn many thousands coots accumulate at open reaches of the avandelta. Before the Caspian Sea level rise a huge number of ducks (mallards, pintails, garganey teals, European teals, gadwalls, wigeons and red-crested pochards) spent the summer molting period within the Reserve. Accumulations (displays) of molting ducks start forming from June. First come mallards, then pintails, gadwalls, later, teals. The displays are situated in solitary areas not attended by people, with rich pabular vegetation and good flowage. Here in July-August form accumulations of 0.2-6 thousands of molting ducks. At Obzhorovsky cluster they are concentrated in the coastal waters near Blinov island, at Damchiksky cluster, near Makarkin island. Due to low flowage, no massive ducks molting areas are formed at the Trekhizbinsky cluster. In mid August, molted ducks remain in molting areas, and then shift to open shallow waters of the avandelta. Annually up to 25 thousand ducks molted within the Reserve. Of special interest are colonies of Ciconiiformes and Pelecaniformes. Willow forests serve as their main nesting areas. Here is noted the rare phenomenon: for many years at all clusters exist colonies where nest together grey heron, pond heron (Ardeola ralloides), great egret, little egret (Egretta garzetta), night heron (Nycticorax nycticorax), spoon-bill (Platalea leucorodia), glossy ibis (Plegadis falcinellus), and rarely buff-backed heron (Bubulcus ibis). Cormorants nest separately, but also may settle in herons’ colonies. In 1981-1985, 7500-9000 cormorants and 1800-4700 Ciconiiformes have been nesting within the Reserve. The population size of these species has been changing within natural limits peculiar to local populations. Cormorants and herons fly feeding to the shallow sea armlets, or kultuks, and to spring floods rich with fish and water invertebrates. In varying conditions cormorant is the most ecologically flexible specie. In colonies of the Reserve nest about 30% of their total delta amount. Especially large colony has been formed at Obzhorovsky cluster (7250 nests). Colonies of cormorants and Ciconiiformes play an important role in ecosystems of the lower Volga delta ecosystems. In areas of mass nesting a large amount of mineral (excrement) and organic matter (eructation, dead nestlings, eggs) come into water, which influences the biogenic matter concentration in kultuks and channels. Feeding on fish, colonial birds take part in transformation of live organic matter through water reservoirs of the lower delta. Many animals keep at colonies of the fish-feeding birds. Wild boar likes to come here to eat nestling food remains or nestlings that dropped out of their nests. For the same reason here comes wels. White-tailed eagle catches fish eructated by cormorant. Among nests of cormorants and herons constantly whisk numerous ravens (Corvus cornix), gathering abundant tribute of eggs and nestlings. The colony lives intensively starting from the coming of first cormorants in March until late July, when all the nestlings spread their wings and leave their birthplace. Heron, spoon-bill and glossy ibis do not visit colonies until the next year; cormorant comes to colony overnight if it is located in the kultuk zone, until late Autumn. Formerly numerous pelicans were nesting at Damchiksky cluster but due to environment change their nesting areas have moved to the avandelta outside the Reserve over 20 years ago. Last years several Dalmatian pelicans (Pelecanus crispus) (up to 10 pairs) were nesting near the southern boundary of the Damchiksky cluster. Annually in July-August near the southern boundary of the Obzhorovsky cluster’s buffer zone form accumulations of migrating Dalmatian pelicans of 3000-4500 specimens. In September they usually shift, but under favorable conditions may stay here the whole autumn. Great-crested grebe (Podiceps cristatus) is numerous in waters of the kultuk zone and the avandelta. It prefers nesting in reed mace beds and by the sides of reed beds and also in open water at the most shallow areas of the avandelta forming colonies up to 100 and more pairs. The largest accumulation of 350 nests has been discovered near the southern boundary of the buffer zone of Obzhorovsky cluster. Whiskered tern, black tern, white-winged tern and common tern (Sterna hirundo) are common within the Reserve. Especially numerous is whiskered tern, which forms colonies in July-August over floating aquatic vegetation at kultuk zone and near avandelta islands. Zooplankton at terns’ colonies is significantly richer than outside. Bird accumulation attracts predacious fish species – wels, pike, and also large lake frogs which feed on tern nestlings. After young terns learn to fly, numerous flocks of whiskered tern and other terns keep to nesting areas for a short time and in September shift away from the lower delta. White-tailed eagle is the most numerous prey bird specie. It can be considered as the landscape specie of the seashore part of the delta. Long-term monitoring of its population has showed that the population is stable, within the Reserve the population is increasing. In autumn one can observe the unique scene of white-tailed eagle accumulation – up to 10 birds sitting on one tree, including young and migrating birds.
Groups of forest and reed complex, especially perching birds, are distinguished by high diversity and number.