117 nests of Red-breasted Flycatchers in Białowieża primeval forest (NE Poland) were characterised. Most nests (79%) were built in Hornbeam Carpinus betulus and lime Tilia cordata. Three types of nest sites were distinguished: chimney shaped (26.4%), half cavities (46.4%) or shelves — the nest was wedged under a piece of bark against the main trunk (27.3%). Most cavity entrances were exposed to the south. Compared to other species of secondary cavity nesters in Białowieża National Park, Red-breasted Flycatchers used cavities of a different shape, with a smaller bottom area and at a relatively low height above the ground (x̅= 4.9 ± 3.13 m). Nesting trees had a smaller diameter (x̅= 31.2 ± 21.4 cm) and were more often dead (29.8%) than trees used by the other secondary cavity nesters. Only four nest sites were used in consecutive seasons.
Territoriality in Red-breasted Flycatchers was studied in the Białowieża Forest of Eastern Poland during five consecutive breeding seasons (2000-2004). In total 99 males were individually marked, and evidence of polyterritoriality was found in 10% of them. The proportion of polyterritorial males varied from 0% (in 2003) to 13.6% (in 2001). The mean distance between the first and second territories was 278 m (± 179.37, n = 10). The rate of polyterritoriality was not related to age class, as older males defended dual territories that were, on average, not more distantly separated than those of younger males. One case of polygyny was recorded. To our knowledge, this is the first evidence for polyteritoriality and polygyny in male Red-breasted Flycatchers.