Background. A scarcely studied consequence of urbanization is the effect of the temporal stabilization of habitat structure and resources on bird communities. This alteration is thought to dampen environmental variations between day and night, seasons and years, promoting a temporal persistence of bird composition in urban environments. The aim of this study is to review actual evidence of temporal stabilization of habitats and resources in urban environments, and its potential effects on the temporal variation of bird species presence among different temporal scales.
Methods. Selection of literature was made by searching published articles and book chapters using Google scholar. I only included articles that compared the temporal variation of bird composition or resources between different levels of urbanization.
Results. In general, there is evidence of temporal stabilization of habitat structure and resources along the three scales considered. At the diurnal scale, the main factor considered was artificial light in the context of light pollution. At the seasonal and interannual scales, several case studies found a lesser temporal variation of primary productivity in urban areas compared with natural and rural areas. Bird species composition showed more stabilization in urban environments at the three temporal scales: 1) several case studies reported bird feeding at night, associated with artificial light; 2) studies in urban parks and along urbanization gradients showed lower seasonal variation of bird composition in the more urbanized areas; and 3) in general, case studies along urbanization gradients showed lower interannual variation of bird composition in the more urbanized areas, although some studies showed no relationships or opposed trends than expected.
Discussion. The published evidence suggests that urban areas dampen the natural cycles at several temporal scales. The stabilization of biotic and abiotic factors, such as light, temperature, food and habitat structure are desynchronized from natural diurnal, seasonal and interannual cycles. However, there is a dearth of studies that simultaneously analyze the relationship between resources and bird composition stabilization. I also emphasize the need to differentiate spatial and temporal homogenization of avifaunas for a future research agenda. Moreover, the relationship between urbanization and other taxa is also commented. Finally, I propose suggestions for future work at different spatial scales.