Humans’ large influence on the environment has constructed many new ecological niches, such as in urban areas. Phenotypic changes, including morphological ones related to human influence, are known from a small number of bird species. The amount of change in a given time period, that is, the rate of change, may vary. Rates of change (both evolutionary and through phenotypic plasticity) are reportedly rapid in human-influenced settings, although this is disputed. We present new data on changes in beak dimensions and rates of change over historical time periods in four urban bird species (Common Chaffinch, European Greenfinch, Eurasian Blackbird, House Sparrow) from three Swiss cities (Basel, Bern, Geneva). Our study shows that beak dimensions have changed little in most investigated urban bird populations over the past century. Only in Genevan Blackbirds there was evidence for an increase in beak length over the past 65 years; Bernese Chaffinches appear to be trending toward a decrease in beak width over the past 55 years. Rates of change in our sample in comparison with literature records showed that compared to populations less influenced by humans, urban evolutionary rates appear to be similar. Although in accordance with previous findings about other urban bird species, our study exemplifies the difficulty to find universal patterns in tempo and mode of phenotypic evolution in urban areas, even when considering the same taxa. Our data contribute to the expanding field of urban evolutionary biology, which is particularly important regarding the growing urban habitats worldwide.

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Featured Image: Figure 1 by Hüppi & Geiger (2022)

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