Aviary observations revealed particularities of foraging behavior in seven species of leaf warblers of the genus Phylloscopus, which sympatrically inhabit the middle-taiga Yenisei. The differences...

Работа проведена в подзоне сухих степей Саратовского Заволжья в течение шести сезонов (2010–2015 гг.). Исследовали характеристики местообитаний, влияющие на структуру популяции варакушки (Luscinia svecica). В районе проведения работ чередуются биотопы с резко различной динамикой условий в течение гнездового сезона. Мы оценивали выбор местообитаний по плотности населения и пространственному распределению участков в каждом из них, а результат этого выбора – по итоговой продуктивности размножения. Плотность населения варакушки всегда выше в равномерно пригодных местообитаниях, где присутствуют необходимые условия для устройства гнезда и кормления. Часть популяции занимает местообитания худшего качества, которые, вероятно, могут быть “резервными” на случай экстремальных условий в отдельные сезоны. Помимо этого проведена оценка вклада разных репродуктивных параметров в итоговую продуктивность размножения. По результатам данного исследования, начало и длина фертильного периода, а также гибель гнезд являются основными параметрами, определяющими различия в продуктивности размножения в разных местообитаниях и в разные сезоны. Полученные результаты обсуждаются с точки зрения вклада отдельных частей популяции в...

The present study was performed in the dry steppe subzone of the Saratov Trans-Volga region during six breeding seasons (years 2010–2015). Habitat features that affected the structure of bluethroat (Luscinia svecica) population were analyzed. The biotopes present in the area investigated differed greatly with regard to the dynamics of environmental conditions during the breeding season. Population density and spatial distribution of nesting territories in each habitat were used to characterize habitat selection, and the breeding productivity was used to assess the result of this selection. Bluethroat population density was always higher in uniformly suitable habitats that provided favorable conditions for nest building and feeding. Part of the population occupied habitats of a lower quality; however, these habitats might be used as “reserve habitats” during breeding seasons characterized by extreme conditions of the environment. Moreover, the contribution of a number of reproductive parameters to the overall breeding productivity was assessed. The present study showed that the starting date and length of fertile period, as well as nest mortality, are the major parameters that determine the variation in breeding productivity between different habitats and seasons. The results are discussed in view of the contributions of population groups to reproduction.

Colonizing populations at the leading edge of range expansion are expected to have a reduced genetic diversity and strong genetic structure caused by genetic drift and allele surfing. Until now, few studies have found the genetic signatures of allele surfing in expanding wild populations. Using mtDNA markers, we studied the genetic structure of the population of midday gerbils (Meriones meridianus) expanding their range to the west in Kalmykia (southern Russia) following the new cycle of desertification, re-colonizing areas abandoned in the mid-2010s. In the colonizing population, we found a reduced genetic diversity, the redistribution of haplotype frequencies—in particular, in favor of variants rare in the core population—and strong genetic structure combined with strong differentiation from the core population—patterns suggestive of allele surfing on the wave of expansion. In terms of genetic diversity and spatial structuration, the western edge population sampled in 2008 before its collapse in 2017 occupies the intermediate position between the current colonizing and core population. This suggests that reduced genetic diversity and increased genetic differentiation are general features of marginal populations, enhanced by the founder and allele-surfing effects at the leading edges of expanding ranges.