Abstract: One explanation for the latitudinal gradient of biodiversity is that evolutionary rates of traits that are important to speciation (e.g. color pattern, song) vary across latitude. The reasons for this include sympatry of sister species, effective population size, breeding season length and generation time. Sister species in sympatry encounter intense interspecific competition and cost of hybridization, which may lead to faster evolutionary rates through displacement of traits. Genetic drift can accelerate evolutionary rates in populations with a small effective size. Traits of sexual selection may undergo faster evolutionary rates in birds at higher latitudes that have a shorter breeding season. There is more accumulated divergence in traits among species with shorter generation time, even though the evolutionary rates are unchanged. In birds, color patterns and song features are essential for territory defense and mate attraction, and these features evolve faster in birds at high latitudes based on the studies from New World bird taxa. We further discussed the phylogenetic approach and variable selection in studies of evolutionary rates of avian traits. Quantification of divergence in traits from the bird’s viewpoint, including evolutionary tradeoff between color patterns and song features, may need to be taken into account in future research. In addition, we argue that more attention should be paid to Asian birds.

Key words: urban forest, density-group index, seasonal dynamics, redundancy analysis., soil meso- and micro-fauna