Diurnal rhythms of locomotor activity, changes in body mass and fat reserves, standard metabolic rate, and respiratory quotient in the free-living coal tit (Parus ater) in the autumn-winter period

Abstract

These studies were conducted in 1999–2010 on the territory of the Zvenigorod Biological Station of Moscow State University (western Moscow suburbs, 55°44′ N, 36°51′ E). Birds (Parus ater) were caught by mist-nets. All the birds were banded and weighed, and their fat reserves were determined; then, the birds were released. A total of 85 individuals were caught. The standard metabolic rate and respiratory quotient (by the method of indirect calorimetry) were measured in 46 experiments with 16 birds. Two peaks were distinguished in the daily locomotor activity: a strongly pronounced daily peak (from 6 a.m. to 4 p.m.) and a weak evening peak (from 6 to 10 p.m.). The body mass did not change during the day. However, some trend for an increase in the mean body mass toward the middle and end of the day was noted. The fat reserves drastically changed during the day. The metabolic rate and respiratory quotient had a well-pronounced diurnal rhythm with minimal values at night (from 12 p.m. to 4 a.m.) and maximum values in the afternoon (from 12 a.m. to 4 p.m.). The total energy budget of Parus ater in the autumn-winter period, energy balance, and the maintenance of constant flying weight along with the dynamics of fat reserves are discussed.