Ecological Population Status of the Most Common Bird Species in Northern Altai Low-Mountain Forests and the Principal Difference in Avifauna Status in Altai and Baikal Regions

Abstract

In 2016 and 2017, from April to July, bird individual nesting home ranges were regularly mapped along the permanent census route (2.8 km) in the low-mountain forests dominated by pine and birch. For each bird species, the nesting densities and average sizes of the bird individual nesting home range were estimated, and raster maps of spatial allocation (MSA) at the scale of the raster grid of 50 × 50 m were obtained. The degree of spatial conservatism (DSC) for each local population was inferred from the pairwise comparisons of the specific MSAs obtained at the same area (28 ha) in different years with the use of the Gamma rank correlation method. The statistical dependence of the population habitat area on DSC was demonstrated earlier (Cherenkov, 2017). The more habitat area is found within the trial plot, the less dependent (random) the individual spatial allocation within a population is observed in different years. Significant DSC estimates (p < 0.05) were obtained for 15 species, and their habitat areas and habitat saturation were found. The population status was inferred from the degree of habitat saturation. Average estimates of the degree of habitat saturation were close in migratory and nonmigratory species (49 and 45%, respectively). The Altai migratory birds wintering in Southeast Asia did not differ statistically in the degree of habitat saturation from those wintering in Southern Europe and North Africa. A comparison of avifauna status of the Altai and Baikal regions revealed substantial differences. In Altai the number of the most common migratory nesting species is almost twice as high, their average nesting density is four times higher, and habitat saturation is twice as high as in the birds of the Baikal region. The interregional differences in the degree of habitat saturation indicate that most of populations of the migratory species of the Baikal region are subject to twice as much intensive pressure of some factors limiting the population growth compared to the Altai populations. At the same time, there were no significant differences in the ecological population status of the nonmigratory species between these regions. Close estimates of the degree of habitat saturation in nonmigratory species in the Altai and Baikal regions support a suggestion that the integrate influence of factors limiting their population numbers is similar in both regions. Close estimates of the degree of habitat saturation and nesting density in the migratory and nonmigratory Altai species show that neither of the two strategies of surviving gives a pronounced advantage. The difference between the Altai and Baikal regions in the degree of habitat saturation in the migratory species is seemingly determined by the different mortality levels in the wintering areas and on the routes of migrations.