Is Urbanization endangering birds?
Urbanization brings with it a significant transformation of the green areas into impervious polluted surfaces due to the constant activities of humankind. The natural green habitats of birds are transformed into anthropogenic structures. As a result, for the bird communities to survive in this new habitat, they have to adapt to the new surroundings, modify their ways to accept the changes or avoid the changes in the landscape.
There are around 10,000 recognized bird species around the world. While some are found explicitly in particular areas, some birds like House sparrows and Feral pigeons are cosmopolitan and can be sighted across the globe. We will discuss some research work that studies the impact of urbanization on bird communities.
When did urbanization begin?
The history of destructing the forest areas into massive building structures dates back to the Roman civilization. With western industrialization during the 1700s, urbanization began on a global level. Population expansion has resulted in urbanization and also contributed to climate changes. These factors together are a threat to the bird communities. While urbanization has led to the loss of some species, there are few which have flourished.
In what ways does urbanization threaten the bird communities?
There are examples of bird communities getting threatened due to urbanization on different levels in an urban setting. Figure 1 depicts specific urban changes that have a negative impact on bird communities.
Figure 1: Multiple urban stressors affecting bird communities.
Source: (Tietze, Dieter Thomas (2018). [Fascinating Life Sciences] Bird Species (How They Arise, Modify and Vanish) || Impact of Urbanization on Birds. , 10.1007/978-3-319-91689-7(Chapter 13), 235–257. doi:10.1007/978-3-319-91689-7_13)
The following highlights explain how urbanization is affecting bird communities:
- Vanishing of species: Some bird species choose to avoid urbanization. This may be due to change in the insects present in the area, fear of humans, low fertility, and migratory nature. High rate of bird predation, high levels of noise and air pollution, collisions with vehicles, predation at feeding tables result in reducing the fitness of the bird
- Change of species: Urbanization provides a platform to study evolution in bird communities. Scientists have noted differences in some birds’ morphological and physiological traits in urban species and their nonurban
- A barrier to birds’ movement: Certain bird populations feel trapped in urban landscapes, especially species with sedentary habits. As a result, they start growing in the given area. Such species show divergence from the original species.
- Bird color homogenization: Highly urbanized areas may be inhabited by a few species with more similar colors than expected by chance, indicating that urbanization is an environmental filter for bird plumage colors.
- Effects of pollution: Emissions from vehicles, metal industries, chemical industries shoot up the toxic gases content in the air. This negatively impacts the health of the birds. Many birds have shown deposition of the pollutants in their feathers. It is also challenging to find a peaceful area in urban settings; continuous moving traffic, building construction work, horns, sirens, alarms all contribute to noise pollution. Furthermore, constantly lit urban areas do not provide the necessary darkness to some bird species. Human encounters with birds, especially during the breeding season, also affect the bird communities
- Environmental filtering of bird communities: Some scientists have reported a functional decline in almost 20% of bird species due to urbanization. The functional richness of farmland birds, especially insect-eating birds, is negatively affected due to urbanization.
- Loss of biodiversity: Urbanization has led to the loss of biodiversity of the bird communities. This may lead to the homogenization of bird communities leading to a severe impact on the ecosystem.
The worldwide examples show the negative impact of urbanization on birds. However, it is evident from the studies that urbanization is a threat to bird communities and has also affected the whole ecosystem. One study has suggested that with the help of proper management, the urban environment may provide the potential to support bird communities. Nesting sites, shrub nesters, food availability, may be provided to birds to increase the bird density in a particular area. We, as responsible citizens, should try and make the life of bird communities better in our urban settings.
Delaney KS, Riley SP, Fisher RN. A rapid, strong, and convergent genetic response to urban habitat fragmentation in four divergent and widespread vertebrates. Plos One. 2010 Sep 16;5(9):e12767.
Isaksson C. (2018) Impact of Urbanization on Birds. In: Tietze D. (eds) Bird Species. Fascinating Life Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-91689-7_13. DOI: https://doi.org/10.1007/978-3-319-91689-7_13
Kurucz K, Purger JJ, Batáry P. Urbanization shapes bird communities and nest survival, but not their food quantity. Global Ecology and Conservation. 2021 Apr 1;26:e01475.
Leveau, L.M., 2019. Urbanization induces bird color homogenization. Landscape and Urban Planning, 192, p.103645.
Manjula M, Mohanraj R, Devi MP. Biomonitoring of heavy metals in feathers of eleven common bird species in urban and rural environments of Tiruchirappalli, India. Environmental monitoring and assessment. 2015 May;187(5):1-0.
Marcacci G, Westphal C, Wenzel A, Raj V, Nölke N, Tscharntke T, Grass I. Taxonomic and functional homogenization of farmland birds along an urbanization gradient in a tropical megacity. Global Change Biology. 2021 Oct;27(20):4980-94.
Tietze, Dieter Thomas (2018). [Fascinating Life Sciences] Bird Species (How They Arise, Modify and Vanish) || Impact of Urbanization on Birds. , 10.1007/978-3-319-91689-7(Chapter 13), 235–257. doi:10.1007/978-3-319-91689-7_13