Assessment of thermohumid conditions within geographical ranges of widespread bird species (on the example of capercaillie: Tetrao urogallus, T.parvirostris)

Clear insight of the impact of climatic factors on animals is necessary to understand their adaptive reactions to the changes in the environment. However, it is difficult to cover all the complex of climatic factors influencing the animals. We studied the dependency of the mean annual air temperature and the total amount of precipitation on latitude, longitude and altitude in the area of wide-spread bird genus – capercaillie. More than 70 plots from 20 to 2.670 ths km2 in Eurasia were investigated with the help of linear regression models. Each of these plots was entirely or partly the habitat of one of the 89 regional populations of western (Tetrao urogallus) or black-billed capercaillie (T.parvirostris). For each of these populations the values of temperature and precipitation were calculated by mean of these models, which showed quite expected location of populations on the thermo humid plane (X – temperature, Y – precipitation). In warmer conditions, the capercaillie occupy the spaces with wider range of precipitation. Along the axis of precipitation, almost all the populations of T.parvirostris lie inside the range of extreme values obtained for populations of T.urogallus and occupy a smaller part of this range. The revealed regularity of the spatial variation of temperature and precipitation (their integral gradient) within geographical range of the Western-European subspecies (T.u.major, T.u.cantabricus, T.u.aquitanicus, T.u.rudolfi): the warmer, the less precipitation - fundamentally differs from that in the range of the rest subspecies of genus Tetrao (the warmer, the more precipitation). The principles of adaptation of warm-blooded animals to different thermo humid environmental gradients are discussed.