Ornithological studies in Central Yakutia

Study of the grasshopper warbler’s (Locustella) biology in the north-east of Asia is closely connected with issues of interaction of closely-related species of these birds. For instance, the areal of the Middendorff’s grasshopper warbler (Locustella ochotensis) inhabiting the coast of the Sea of Okhotsk, overlaps that, of the Pallas’s Grasshopper Warbler (Locustella certhiola), which is spread in continental parts, that gives an occasion to their hybridization. In this regard specification of various life aspects of those species is possible only during study of “pure forms”. Central Yakutia represents a convenient region for studying of the Pallas’s Grasshopper Warbler’s biology.

As a territory for field work we chose an area, located 30 km apart from Yakutsk, actively used as a model by the colleagues-ornithologists from the Institute of Biological problems of Cryolithozone SD RAS. The long-term studies have being conducted there, dedicated to biology of the sedentary birds – Siberian jay (Perisoreus infaustus) and willow tit (Parus montanus); cavity nesters, first of all, the red-breasted flycatcher (Ficedula parva) and semiaquatic birds, typical representative of which is the water rail (Rallus aquaticus indicus). Study of the predatory birds and the grouses has been also not overlooked. In general, the studied area (about 16 km²) is typical for the plains of Central Yakutia represented by alases (slightly slopping and flat-bottomed hollows of several km in diameter and up to 30m deep) with lakes,  coniferous (pine and larch) and deciduous (birch and willow) forests. Closeness to the town adds the elements of anthropogenic landscape – cultivated and overgrowing plowed fields.

          

A complete search of the nests was being realized for two summer months (June-July), 2017, over the nest sites of the Pallas’s grasshopper warbler, followed by the birds’ watching, descriptions of the colony’s density, nesting phenology and breeding success. In the studied region the Pallas’s grasshopper warbler represents the numerous species inhabiting valleys of the small rivers, alases and boggy areas. In early July they arrive at the nesting places among the last migrants from the wintering areas, located in the countries of South Asia. The “arrival” can be heard by the songs of territorial males typically in the morning. Sexual dimorphism is absent for this species. Weight of the adult birds varies from 14 to 16g. The birds have the hidden lifestyle, preferring moving in the thick bed of grasses to flights. They build their cup-shaped nests in the sedgy tussock bog, grass beds and shrubberies. They use dry leaves and stems of grass as building material. Construction is completely in charge of the female. In the second decade of June the egg laying starts. Every morning the female lays one egg staying close to the nest during the day. The complete laying consists of 4-6 dark-olive eggs. Brooding lasts for about two weeks. New-hatched chicks are about 2g each. Both parents participate in feeding of chicks with insects. The chicks stay in the nest for 11-13 days and then leave it. For some time the birds keep all together in recent area and then start migrate to wintering grounds. Mass migration takes place in the mid-August.

 

          Biotopes, similar to those, of grasshopper warblers, are occupied by the water rail - a representative of the rails family (Rallidae), the Gruiformes order (Gruiformes). It refers to the semiaquatic birds, about 180g, nesting over the wetland with sedgy tussock bog. It has exclusively concealed lifestyle; in case of danger it immediately hides itself in the reed or sedge beds. They build nests in the sedgy tussock bog; complete laying has 11-13 light eggs. In one day after hatching the chicks fledge and abandon the nest. Despite the high breeding density, a lot of issues of biology of this species also need detailed studying that is impossible without the direct catching and individual tagging of the birds. Up to now there were no specific methods of catching of the water rails. Due to the work carried out, different catching methods of those birds were developed and tested. oth parents participate in feeding of chicks with insects. The chicks stay in the nest for 11-13 days and then leave it. For some time the birds keep all together in recent area and then start migrate to wintering grounds. Mass migration takes place in the mid-August. font-style:normal'>Parus montanus); cavity nesters, first of all, the red-breasted flycatcher (Ficedula parva) and semiaquatic birds, typical representative of which is the water rail (Rallus aquaticus indicus). Study of the predatory birds and the grouses has been also not overlooked. In general, the studied area (about 16 km²) is typical for the plains of Central Yakutia represented by alases (slightly slopping and flat-bottomed hollows of several km in diameter and up to 30m deep) with lakes,  coniferous (pine and larch) and deciduous (birch and willow) forests. Closeness to the town adds the elements of anthropogenic landscape – cultivated and overgrowing plowed fields.

Typical nesting biotope of the water rail Tagging of the water rail (photo by M.I. Makarov)

    

Beside the study of nesting biology of the particular species we have collected data on faunal diversity of the studied territory. Occurrences of birds were recorded by voices and using binocular glasses, besides, photographic surveying was done. Data obtained will join the array of the long-term watching of the studied region.

Material is provided by Y.A. Sleptsov