THE MAXIMUM, POTENTIAL PRODUCTIVE AND NOR MAL LEVELS OF THE METABOLISM OF EXISTENCE IN PASSERINE AND NON-PASSERINE BIRDS .2. CORRELATIONS WITH THE LEVEL OF EXTERNAL WORK, ENERGETICS AND ECOLOGICAL CONDITIONS

26 species of passerine birds covering almost the entire sizerange of the order (from Regulus regulus (body weigth is 5.5 g) to Corvus corax (1208 g)) and 16 non-passerine species with similar size-range (25 to 4000 g) were studied. The maximum power of the metabolism of existenc e was measured to determine the amount of energy that birds can posses s at any T-A. To determine the working capacity in passerines and non- passerines, MPE and BM must be compared in both groups. The MPE/BM rat io is the principal coefficient of power, which is practically equal b oth for the level of the regression lines and for their slopes in pass erine and non-passerine birds: Passerines: MPE/BM((W)) = 4.7m(-0.0515) , MPE/BM((S)) = 4.7m(-0.038) Non-passerines: MPE/BM((W)) = 5.3m(-0.048 ), MPE/BM((S)) = 4.7m(-0.023). The optimal temperature for the product ive process was estimated using the equation MPE = h(max) . (T-B - T-o pt) and T-opt = T-B - MPE/h(max). It is practically equal to T-lo and coincides with its variation. T-opt in passerines is significantly low er than in non-passerines. Different exponents in the equations descri bing the correlation of MPE, PPE and BM with body weight show greater working capability of small birds, especially in passerines. This ener getic feature allows the small forms of passerines to survive better i n the regions with low temperatures, where they find sufficient amount s of food. These data allowed us to propose a new point of view, that the increase of BM in a bird should increase potential energy (MPE) an d potential productive energy (PPE), and that BM is an index of the le vel of external work (EW). Empirical data show, that daily energy expe nditure (DEE) of the studied species depends on the ambient temperatur e and can be described throughout the year by the following equation: DEE = h . (T-B - T-A) + a . BM, (1) where DEE - daily energy expenditu re at any level of activity (a) and at any ambient temperature (T-A), h - thermal conductance, which changes from minimum (h(min) at the max imum isolation and/or the minimum level of activity) to maximum (h(max ), at the minimum isolation and/or the maximum level of activity), a - the level of activity (at a = 0, DEE = SM, at a = 1, DEE = EM), T-B - body temperature (40 degrees C in birds), T-A - ambient temperature, BM - basal metabolism. Thermal conductance of a bird in active state i s equal to h(l) . (1 - p . a), because a part of metabolic energy is t ransformed into the mechanical one, and takes place the compensation o f thermoregulatory expenditures. The value of BM is an index of the le vel of daily external work (EW):EW = p . DEE. Thus, DEE can be represe nted as: DEE = h(l) . (1 - a . p) . (T-B - T-A) + a . BM, hence EW = h (l) . (1 - a . p) . (T-B - T-A) + a . p . BM. Naturally, the total lev el of activity throughout a day is not higher than 4, because the diss ipated heat can be increased no more than 4 times without the increase of evaporation. Thus, the ratio h(max)/h(min) = 4. If the maximum val ue a = 4, we have the equation as follows: EW = h(f) . (1 - 4 . 0.25) . (T-B - T-A) + 4 . 0.25 . BM. The maximum productive capacity of home othermic animals is possible at T-A = T(l)o and DEE = 4BM. Thus, at T- A = T-lo, EW = BM. Thenabalysis of allometric correlations for MPE, PP E, MPE/BM and PPE/BM shows, that energy advantage of passerines takes place at the body weights ranging from 5 to 150 g. In the range from 1 50 to 600 g, the energy capacities of passerines and non-passerines ar e approximately equal, and if the body weight is more than 600-800 g, non-passerines have the advantage. The range of 5 to 150 g in forest h abitats is almost completely occupied by passerine birds. That is the result of their high energy capacity.