The study of bathymetry, macrozoobenthos abundance and the Russian desman population has been performed in the water bodies located in the Prisurskiy State Nature Reserve buffer zone (River Sura lower reaches floodplain). Twenty-one water bodies were examined in total. In six lakes, Desmana moschata (Russian desman) was absent. In nine lakes, the settlement density was less than 5 burrows per 1 km coastline. And in six lakes, the settlement density was high (i.e. more than 5 burrows per 1 km). The studied parameters of the lake basin included the depth of the lake, the water acidity (pH), dissolved oxygen concentration, the type of the plant cover of the shoreline (forest, shrub, steppe), and anthropogenic load. The taxonomical analysis and individual weighing of the animals in the macrozoobenthos samples were performed. All the parameters were then included to an analysis of the Russian desman density. The factors affecting the density of the Russian desman burrows were revealed. The water bodies having more than five burrows per 1 km along the shoreline are characterised by a higher abundance of macrozoobenthos and especially by the highest mollusk biomass. In turn, the abundance of mollusks, the main food, depends on the dissolved oxygen concentration in the water, trophic state of the lake, and the bottom slope. The highest density of the Russian desman was registered in the lakes characterised by a high biomass of the gastropods Lymnaea stagnalis and Viviparus (Contectiana) contecta. It was noticed that the Russian desman preferred to inhabit wide-course water bodies characterised by a high density of trees or bush along the shoreline. Therefore, the factors mentioned above may appear as the indirect characteristics of the water body with optimal habitat conditions for the Russian desman. Other water body characteristics, such as depth, may define the temporary optimum conditions for the Russian desman inhabiting. The combination of different conditions in a certain area allows the Russian desman to choose suitable water bodies, depending on the annual climatic conditions. There is a combination of a steppe (meadow) and forest areas in the River Sura lower reaches floodplain. Thus, this floodplain may be named as the most suitable for the Russian desman inhabitance.

The paper presents an overview of the phenomenon of range expanding of birds located at the northeastern limit of their range. The study area is located in the Volga-Kama Krai in the Chuvash Republic, adjacent to the River Volga. It is situated northwards and southwards of 56° N, and westwards and eastwards of 49° E, in a band of about 400 km. The problem is considered in aspect of the intra-century changes of climatic conditions in the region and in European Russia as a whole. The analysis of the relationship between the range expansion of some bird species and the intra-century climate changes was based on ornithological and climatological material available for the study area. We have used material on climate change in the Chuvashian Republic and Volga-Kama Krai since 1926, taking into account recent data of Roshydromet and Intergovernmental Panel on Climate Change. The idea of this study was based on the theory of climatic cycles of different periodicity, the theory of recent global climate change and the hypothesis of cyclic dynamics of the ranges of waterfowl in the context of centuries-old and intracentury climate change in Northern Eurasia. In the framework of the problem, we have studied ornithological material dated from the late 19th till the early 21st century, authored by Bogdanov, Ruzsky, Zhitkov, Buturlin, Artobolevsky, Volchanetsky, Pershakov, Popov, Glushenkov and others. As shown the intra-century climate changes do quite likely affect the northward and northeastward range expansion of such bird species as Cygnus olor, Anas strepera, Aythya ferina, Hieraaetus pennatus, Aquila heliaca, and Fulica atra. Climate changes can also be judged on the base of the shift in the arrival timing to earlier dates for some birds. It is most clearly manifested for early arriving species (Grus grus, Ardea cinerea, Actitis hypoleucos). It is also true for the later arriving Pernis apivorus and Merops apiaster whose existence depends on the emergence time of insects. Climate changes are not the only determining factors affecting the bird distribution. Ecological factors are also important, along with the mentioned above. The range expansion of species in anthropogenically disturbed landscapes occurs by means of complex chains of ecological relationships. Examples of Haematopus ostralegus and Sterna albifrons show the reasons for the reduction and restoration of species ranges due to the change in the effect of an anthropogenic factor. Thus, the range expansion of some bird species to the north and northeast is quite likely related to the centuries-old and intra-century climate changes. However, we do not consider climate warming as the only determining factor in the abundance increase and further range expanding for some birds at the range limits in temperate zone. In order to a better understanding of the impact of climate changes on birds, it is needed to investigate how modern climate changes in the temperate regions influence on the animals which serve as food for birds, and, as a consequence, how these proces...

Мониторинг зимнего населения птиц организован в Нижнем Присурье, на территории Чувашской Республики с сезона 1989-90 гг. � 2000 года у�ет� проводятся на территории заповедника �Присурский� и наци� � 2000 года у�ет� проводятся на территории заповедника �Присурский� и наци� 2000 года у�ет� проводятся на территории заповедника �Присурский� и национального парка �Чаваш вармане�. Регулярн�е у�ет� зимующих птиц осуществляются в рамках программ� �Parus� Мензбировского орнитологи�еского общества РАН, трансформировавшейся в последнее десятилетие в массовую кампанию �Евроазиатский Рождественский у�ет� под эгидой Союза охран� птиц России. За 20 сезонов мониторинга �исленности зимующих птиц в Нижнем Присурье зарегистрировано 44 вида. 11 из них отме�ен� едини�но или редки. У �ет�рех видов-королька Regulus regulus (L.), ополовника Aegithalos caudatus (L.), �ижа Spinus spinus (L.) и щегла Carduelis carduelis (L.)-в на�але, от 1990�х годов до середин� первого десятилетия 2000�х гг. наблюдалось увели�ение обилия, а затем-снижение. У одного вида-малого пестрого дятла Dendrocopos minor (L.) наблюдается обратная картина. Показатели обилия 13 видов в первое десятилетие у�етов-1990�е год�-оказ�ваются в�ше, иногда зна�ительно, �ем в 2000�е и 2010�е. Можно предполагать, �то от�асти разли�ия показателей объясняются спецификой территорий у�етов и у�астков, по котор�м проходили маршрут� в 1990�х гг. и 2000�x гг. Однако для ряда лесн�х видов тенденции снижения обилия отме�аются не только в Нижнем Присурье, но и на других модельн�х территориях зимних у�етов. В целом можно отметить, �то в динамике �исленности зимующих видов птиц Нижнего Присурья, как и на ряде других территорий зимних у�етов в пределах Восто�но�Европейской равнин�, за последние 25 лет преобладали негативн�е тенденции. Ключевые слова: мониторинг, зимнее население птиц, Нижнее Присурье, программа �Parus� (�Евроазиатский Рождественский у�ет�), �исленное обилие.