Whom can we hear singing in European cities?
It is a well-established fact that urbanisation causes fragmentation of the landscape and habitat loss. Moreover, urban environment presents a challenge for wildlife, as it is a dynamic system that changes easily. It is therefore important to understand how urbanisation affects ecosystems in which an increasing number of people are now living. A large international team of scientists, including Jiří Reif from the Institute of Environmental Studies, surveyed birds across 17 cities in 10 European countries. The team asked a quite simple question: Which urban characteristics affect different facets of avian diversity and how?
In urban areas, we are witness to a phenomenon known as biotic homogenisation, which is characterised by the simplification of ecosystems (decline in ecological and functional differentiation leading to a reduction in specialist species). Organisms living in urban areas also experience high levels of artificial light and noise pollution. The negative effects of artificial light at night have been demonstrated for numerous species, including mammals, birds, amphibians, and even insects and plants. In birds, changes in circadian and seasonal rhythms along with behavioural and navigational alterations have been reported. Birds from urban areas have, for example, an impaired capacity to navigate according to the night sky and their migration might also be challenged.
Studies indicate that bird communities in urban areas might benefit not only from urban greenery (overall amount as well as structure) but also from anthropogenic constructions which can serve as sites for nesting or perching. Therefore, the authors of the study recorded the diversity of bird species, along with several characteristics of the urban environment. Moreover, they considered various aspects of diversity that are not generally investigated. For instance, researchers usually focus only on taxonomic diversity (the number of species in a given ecosystem). This measure alone might, however, be insufficient to describe the entire ecosystem and the roles each species plays within it. To address this, the authors also considered functional diversity (the role of the species within the ecosystem) and phylogenetic diversity (relatedness of the species within a community).
Some of the results were not that surprising. For example, the team found that birds are subject to a well-known ecological pattern, where species richness is negatively linked to latitude. Thus, cities in northern Europe were home to fewer avian species, which were also more closely related to each other (lower phylogenetic diversity). The authors also reported that greenery (grass, bushes, and trees) is beneficial for the taxonomic diversity of birds while the density of buildings is detrimental to the number of birds in the communities.
Several insights from the study were, however, more difficult to interpret and less obvious. For example, the authors found that the level of light pollution is linked to higher functional diversity. This effect probably arose as a result of the adaptation of insectivorous birds to foraging in highly illuminated areas. Alternatively, it might have been an artefact caused by the fact that the highest light pollution was detected in Finland, which was also the region with the highest functional diversity. Across all cities, the authors found evidence of phylogenetic homogenisation (bird communities consisting mainly of closely related species), which was linked with the higher density and height of the buildings, an increasing number of pedestrians, and the level of light pollution. Notably, the only characteristic counteracting the tendency towards phylogenetic homogenisation was the density of bushes and shrubs.
With regard to which species of birds were the most common in the cities studied, the top ten recorded species were the following: the house sparrow (Passer domesticus), common blackbird (Turdus merula), common swift (Apus apus), great tit (Parus major), common wood pigeon (Columba palumbus), common pigeon (Columba livia), the Eurasian collared dove (Streptopelia decaocto), the Eurasian magpie (Pica pica), the Eurasian greenfinch (Chloris chloris), and the western jackdaw (Corvus monedula).
Veronika Rudolfová
Published:
Mar 28, 2022 10:50 AM
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