Altitudinal-belt differentiation of the bird population in the north of the Koryak Highland

Knowledge of ecological and geographical patterns of mountain bird fauna and population formation is considered to be one of the most vital issues of modern ornithology. The obtained data can be used in the monitoring and development of biodiversity conservation measures. In our study, we analyzed ecological patterns of the altitudinal-belt differentiation of bird population in the northern spurs of the Koryak Highland. We collected data during expeditions carried out in summer 2014 in Lake Mainitz basin, the Gytgyponytkynvaam river valley and the Tynulve Nangagte ridge (63°8'-63°14'N, 176°42'-176°48'E) (See Tables 1 and 2). Studies were conducted in regions with three distinct altitudinal belts: alpine (500-600 m asl and higher), subalpine (up to 360-560 m asl) and shrubby-dwarf pine belt (up to 100-150 m asl). We used the method of route counting in transects of unlimited width (Ravkin YuS, 1967). The fauna of breeding birds was analyzed according to species belonging to faunal complexes (Shtegman BK, 1938; Kishhinskiy AA, 1976) and geographical-genetic groups (Kishhinskiy AA, 1988; Romanov AA, 2013). We calculated the number of water and near-water species of birds by direct counts, and then recalculated the number of individuals per length unit of the coastline. The reliability of nesting was determined according to the criteria recommended by the European Bird Census Council (The EBCC Atlas of European breeding birds..., 1997). Nesting was considered confirmed upon detection of nests with chicks or eggs, encountering adult birds with food, encountering fledglings or hatches; probable when observing the territorial and mating behavior of birds in habits suitable for nesting; possible when encountering a species in habitats suitable for nesting. Avifauna similarity of compared areas and altitudinal belts was determined by the S0rensen faunal commonness coefficient (Pesenko YuA, 1982; Chernov Yul, 2008). Population similarity coefficient was used to identify differences in the bird population of several areas (Naumov RL, 1964). In the nomenclature and when compiling lists of birds, we followed LS Stepanyan (Stepanyan LS, 2003). The names of some species were taken from The List of Birds of the Russian Federation (Koblik EA et al, 2006). We revealed dominant and subdominant species of high-altitude belts of the investigated areas. Species whose number was 10% of the total population density of all species of the high-altitude belt were considered dominant, subdominant species were from 1% to 10%. We revealed that 76 species of birds breed (40% of whole avifauna of the Koryak Highland) in the investigated areas of the northern spurs of the Koryak Highland (See Table 1). A number of species (n=7) was specified for the first time on the nesting in the northern spurs of the Koryak Highland at a distance of 300-1200 km from the northern boundaries of the main range. The taxonomic structure of the nesting avifauna corresponds to the zonal and landscape features of the Northeast Asia. The species of the groups of Passeriiformes, Charadriiformes and Anseriformes dominate and take 85% in the overall diversity. The nesting aviafauna commonness coefficient of the northern and southern regions of the Koryak Highland is high and equal to 83%. The species richness of the avifauna decreases with altitude. In a wide range of heights, covering at least two high-altitude belts, there are 44 species. The change in species composition of birds occurs gradually with height. The species of the Siberian faunal complex (34%) and widely distributed species (33%) are most significant in the formation of avifauna. The original zoogeographical element of the local nesting avifauna is the species of the American faunal complex. The significant part in the formation of avifauna takes boreal-hypoarctic species (29%) and widespread (26%) geographical-genetic groups. The density of the nesting population of birds is reduced with height. The bird population density in the terrestrial habitats of the shrubby belt is 725 ind./km², 471 ind./km² in the subalpine belt, and 83 ind./km² in the alpine belt (See Table 1). The maximum similarity is observed in the population of birds of the shrubby and subalpine belt (46%), the minimum is the population of shrubby and alpine belt -6.8%). The density of the bird population of water-surrounding habitats varies from 13 individuals per 1 km of the coastline at the river, and up to 30 individuals per 1 km of coastline at the lake (See Table 2 and 3). The paper contains 3 Tables and 36 References.

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