Abstract:

To explore how density of potential cavity resources (including cavities and artificial nest boxes) affects the composition and distribution of secondary cavity-nesting guilds, as well as the community structure of breeding birds, we studied plots with different densities of nest cavities in Dagang Forestry Farm, Jilin Province, China from November 2007 to July 2008. Based on the density of cavity resources, the nine sample sites were divided into three treatments, i.e., NBP (nest-box plots with less cavities and high-density nest boxes), LDP (low-density cavities plots without nest boxes) and HDP (high-density cavities plots without nest boxes). We then surveyed avian communities and noted the use of cavities and artificial nest boxes. All the treatments contained four primary cavity excavators, and three species were the same. Four secondary cavity nesters were widespread in the three treatments, including the great tit (Parus major), marsh tit (P. palustris), yellow-rumped flycatcher (Ficedula zanthopygia) and eurasian nuthatch (Sitta europaea). Total densities of secondary cavity nesters in NBP and HDP were higher than that of LDP. Densities of great tits and yellow-rumped flycatchers were higher in NBP and HDP than in LDP, because they were major users of nest boxes. There were no significant differences in the densities of marsh tits and eurasian nuthatches among treatments. A significant positive correlation was detected between the density of primary cavity excavators and cavity density, and also between the density of secondary cavity nesters and potential cavity resources. Bird species diversity indices were lower in LDP than in NBP and HDP. Nest-box addition could potentially regulate the composition of avian communities by increasing bird species diversity indices. We observed no differences in evenness, species richness indices or probability of interspecific encounter (PIE) among treatments, and Sørensen similarity indices differed little among treatments. There were no obvious differences in structure of breeding bird guilds between HDP and LDP. Nine species were found in all the three treatments, and their densities were not affected by the temporary increase in secondary cavity nesters. We hypothesize that density of primary cavity excavators determines the density of cavities in forests, which may change distributional patterns of secondary cavity-nester guilds, and therefore affect the structure of breeding avian communities.

Key words: cavity, artificial nest box, primary cavity excavators, guild structure, regulation