From late April to the second 10-day period of June 1994–1999, in 76 unmated males the time-budget was measured during 304 hours in a 6.6 km2 area of mature mixed and coniferous forests near Moscow. In 1999, territorial males were counted at least once per pentade throughout the breeding season in a 35 ha plot with 180 nest-boxes. Dark (grades 2–3 on Drost's scale) and pale (grades 5–7) males had similar levels of singing activity, but in cold weather the former had higher song rates than the latter. The singing activity of all the males was relatively low at the beginning of the season (by the mid-May). Dark males sang mainly from open perches (67.6% of songs, compared with 23.2% for pale males). In dark males visual stimulation compensated for the relatively low acoustic activity in early spring when trees were still lacking leaves. The immediate vicinities of nest-boxes occupied by dark males were visited by females significantly more frequently than those of pale ones.
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Vol. 36 • No. 1