How do we make birds feel more at home?

Taking a walk through the busy streets of the city, life appears to be all around us. Bikers briskly pass you by, drivers honk loudly and hundreds of people walk around as if you find yourself in an anthill. A pigeon quickly takes off before a food-courier rushes past. A sea gull tries to snatch a piece of bread from a hungry student traveling home. When leaving the city center the hustle and bustle becomes quieter. A family of ducks are crossing the road to join a group of geese in the pond. You listen carefully and hear the song of a blackbird as the sun slowly sets.

You may not realize it at first, but at least a fifth of all bird species worldwide also lives in our cities (Aronson, 2014). Even though populations can be small, a lot of bird species’ populations persist in urban areas amongst us people. No doubt they also have to navigate the same busy streets as we do, with the same sensory overload. Given the fact that this is not their ‘natural’ habitat, one could wonder how these animals are doing in the cities. How could we help to make our cities a better home for these birds?

More research is being performed on the ways some birds are changing their behaviors or appearance to adapt to urban life. Scientists are finding that some species alter how they sense the world and how they communicate. Hahs et al. (2023) have found that birds from all over the world will have similar traits when living in cities. They call this combination of characteristic the “urban trait syndrome”. They discovered that birds living in urban areas tend to eat a wider variety of food, lay fewer eggs and are smaller than the rural birds of the same species. But birds also alter their communication. For one, some bird species have been shown to sing at higher frequencies and at a higher amplitude in cities than in rural areas (Slabbekoorn, 2003). This is mainly because the low frequency noises of the city (cars, aeroplanes, factories) can prevent some songs from being heard by other birds. This happens especially when birds sing at similarly low frequency. Their song then gets ‘masked’ by the sounds of the city. Singing in a higher frequency with sometimes also a higher amplitude can help the songs to be heard, something that is very important for reproduction or the defense of territory.

Birds adapt to cities, but the adaptations can only help them until a certain point. Bird decline has been occurring rapidly this last century. For instance, North American bird populations have decreased by 3 billion birds since 1970 (Rosenberg, 2019). The world population is only expected to increase, along with it the amount and size of urbanized area. This means that the pressure on birds will only increase, as their natural habitat decreases. How can we adapt cities to make them a better habitat for bird species? Many current urban bird populations are found in city parks or gardens. These are green areas amongst the otherwise concrete environment of the city. Studies show that cities with the highest number of parks and gardens (and the least amount of urban area) tend to have the highest density of bird species (Aronson, 2014). Especially native plants are favourable.  Aside from this, many small parks tend to be better for diversity than lesser large parks (La Sorte, 2023). Increasing the number of city parks could really help increase bird species density. Planting native, non-invasive plant species could provide ample food sources. Secondly, a reduced level of noise and light pollution could also help urban birds. Switching to green light could help nocturnally migrating birds to not get as disoriented as they do with red and white light (Poot, 2008). To prevent noise pollution, sound barriers can be used or noise restrictions set in certain bird-rich areas. Aside from this, encouraging the use of quieter machinery and equipment could help.

Adapting cities to make them more welcoming towards birds will help increase bird diversity and abundance. It is time to make some necessary changes to cities in order to increase biodiversity!

 

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