Diurnal rhythms of standard metabolic rate and respiratory quotient in the coal tit (Periparus Ater, Aves) during the autumn-winter period

Standard metabolic rate of birds has been measured by flow-through respirometry based on their standard O 2 consumption and CO 2 release during the day- and nighttimes in a darkened chamber at a constant temperature of 25°C. The research was carried out in October–March 2009–2013, in the western part of Moscow region. The standard metabolic rate and respiratory quotient of coal tits have well-pronounced diurnal rhythms reaching their minimum in the nighttime (from 2:00 a.m. to 5:00 a.m.) and maximum in the daytime (from 11:00 a.m. to 2:00 p.m.). A significant linear dependence has been found between an increase in the standard metabolic rate and that in the respiratory quotient. The maximum difference between values of the standard metabolic rate during the day- and nighttimes is 55%. It may be concluded that the main elements oxidized at night are fat reserves, whereas proteins, as well as a mixture of proteins, fats, and carbohydrates, are oxidized during the daytime.