Does interspecific competition affect territorial distribution of birds? A long‐term study on Siberian Phylloscopus warblers

Abstract

Seven species of Phylloscopus warblers breed in the middle taiga subzone of Central Siberia. We studied their territorial distribution over 18 breeding seasons between 1978 and 1996. Phylloscopus inornatus, the most abundant breeding bird species in the study area, breeds in dense clusters of territories. In some habitats, these clusters are very unstable from year to year, providing an excellent opportunity to study the influence of P. inornatus on the territorial distribution of other species. We present a method for quantifying decreases in a species’ breeding density caused by the presence of a competing congener. Analysing all possible combinations of species, we found reciprocal territorial avoidance between P. inornatus and P. proregulus as well as between P. inornatus and P. collybita. This is consistent with the hypothesis that territorial avoidance occurs between the species of greatest morphological similarity. The occurrence of territorial avoidance is not explained by habitat characteristics such as vegetation cover and productivity. However low productivity may be necessary for territorial avoidance to occur. An alternative explanation for the observed territorial separation of some species, derived from the Fretwell‐Lucas model of habitat occupancy, is examined and rejected. Causes and implications of clustering behaviour of P. inornatus are also discussed.

Competing for crevices: interspecific conflict influences retreat-site selection in montane lizards

“…This conclusion accords well with the results of studies on many other species of vertebrates showing that interspecific interactions affect habitat use (e.g., Bourski and Forstmeier 2000;Tannerfield et al 2002;Robertson 1996;Jaeger 1971). Some of the best examples of such interference effects come from studies on invasive species, or taxa that are expanding their range in anthropogenically modified habitats.…”

“…Indeed, interspecific interference competition of this kind (as opposed to exploitative competition for limited resources) has been documented in a wide range of taxa from most major vertebrate lineages. Direct social interactions between sympatric species influence habitat use in birds (Reed 1982;Robinson and Terborgh 1995;Pearson and Rohwer 1999;Bourski and Forstmeier 2000), mammals (Brown 1970;Grant 1972;Palomares and Caro 1999;Tannerfield et al 2002), fishes (Shulman 1985;Robertson 1996;Bay et al 2001) and amphibians (Inger and Greenberg 1966;Jaeger 1971;Brodman and Jaskula 2002). Remarkably, however, such interactions have attracted much less study in reptiles, especially squamates (lizards and snakes).…”

Habitat choice in Phylloscopus warblers: the role of morphology, phylogeny and competition

“…In contrast to these findings from Kashmir, our study on territorial spacing in a Central Siberian community of seven species of Phylloscopus warblers (Bourski and Forstmeier 2000) showed that, at this site, the intensity of actual interspecific competition tends to be low. This might be due to breeding communities at northern latitudes being less saturated, as breeding populations of long-distance migrants are often limited by wintering conditions (e.g.…”

Species richness, relative abundances and habitat use in local assemblages ofSorex shrews in Eurasian boreal forests

“…Thus, we prefer to use the pooled abundance of shrews themselves as a measure of habitat productivity instead of any climatic parameters. A similar approach was used eg in the study of interspecific relationships among Phylloscopus warblers (Bourski and Forstmeier 2000). This approach is also consistent with Tilman's (1982) model, and is supported by reported positive correlations between the density of shrews and the density of their food resources (Holling 1959, Yudin 1962, Butterfield et al 1981, Churchfield et al 1997.…”