Roosting of the great tit, Parus major and the nuthatch, Sitta europaea innest boxes in an oak-hornbeam forest

In the years 1998-2000, research into the entitled species roosting in nest boxes was carried out in an oak-hornbeam forest in Central Slovakia. Withi n the study plot almost exclusively the species Parus major (71.3%) and Sit ta europaea (28%, n = 157) could be found roosting during the winter period (October - April). The sex ratio showed a prevalence of the males: Parus m ajor making 67.9M : 32.1F tin n%, n = 112 records) and for Sitta europaea 6 5.9M : 34.1F (n = 44). The highest numbers of roosting birds were found in November (64% of nest box occupancy). Nocturnal occupancy of the nest boxes slightly decreased from November up to April. From the total 157 roosting birds recorded in winter period, 71.3% were recaptures and 45 specimens wer e recorded only once. Roosting site fidelity was considerable and then was no significant difference either between the two observed bird species or b etween the individual sexes within, as well as between the species (P = 0.7 4, one factor ANOVA). The largest roosting territory was for major females (mean area diameter 126 m), the smallest one for S. europaea females (70 m) . The differences between these species in the case of females are marginal ly significant (P = 0.095, t-test). The birds roosted in nest boxes alone, but regularly alternating individuals and species on the roosting sites wer e noted. From 157 records only 10.2% showed repeated occurrence in the same nest box in two successive monthly checks.