Birds living in cities are usually more colorful and less brown

Skylines keep climbing, roads stretch farther, and forests turn into parking lots. Urbanization is everywhere, sweeping across continents and replacing natural habitats with steel, glass, and asphalt.

As cities expand, animals and plants must either adapt or disappear. Among these quiet struggles for survival, birds provide one of the most visible signs of how city life changes the natural world.

Urban ecology has emerged to study these impacts. This field focuses on how animals adjust to city life and how their behaviours, appearances, and chances of survival shift.

While we already know that urban noise affects how birds sing and communicate, questions remain about how cities might also shape something more subtle and striking: their feathers.

Bird colors matter for city survival

Birds don’t just wear colors for show. Plumage color plays many roles in survival. It helps regulate body heat, provides camouflage from predators, and signals strength or attractiveness to potential mates.

In natural habitats, colors evolve slowly through generations. But in urban areas, the rules change quickly.

Cities are warmer than rural areas. They have different backgrounds – grey walls, dark roads, and neon lights. They also have fewer predators and more artificial lighting at night. This creates a unique environment that may favour certain bird colours over others.

That’s where the question arises: are city birds coloured differently from their countryside counterparts? A group of scientists decided to find out.

Data from hundreds of bird species

A research team led by Bart Kempenaers at the Max Planck Institute for Biological Intelligence and the University of Granada took on this question.

The researchers used a global dataset that included the abundance of over 1200 bird species across habitats with different urbanization levels. They combined this with detailed information on each species’ plumage colour.

The goal was simple but powerful: could plumage color predict which birds do well in cities? The results revealed clear patterns.

The researchers discovered that birds that succeed in urban areas tend to be less brown than those that don’t.

“Brown shades are more common in natural environments than in cities. We suspect that brown birds are at a disadvantage in a rather grey city. The predominant colors of a city and the lack of suitable habitats can therefore determine which bird species are successful there,” explained Kaspar Delhey, one of the lead authors of the study.

Urban birds seem to shed their earthy tones and adopt colors that fit – or even stand out – against the urban backdrop.

Colorful birds do better in cities

The findings went further. Not only do city birds avoid brown, but they often display more elaborate and striking plumage, especially among females. This trend runs counter to what might be expected in the wild, where standing out can attract predators.

Cities, however, are relatively safe. With fewer predators lurking in the shadows, birds no longer need to hide as much. As a result, colors that once would have been risky may now help with recognition, mating, or dominance within species.

This supports a new understanding of urban wildlife: cities don’t just change numbers – they change traits. The environment influences how birds look, and colour becomes more than just decoration.

Cities have fewer birds but more variety

Earlier studies had suggested that cities reduce the diversity of colors in bird populations. With fewer species around, people assumed the range of colors would also shrink. But this research turned that idea on its head.

“There are fewer species in urban areas than in rural areas. When we take this into account, the bird communities in cities actually have greater color diversity,” said Juan Diego Ibáñez-Álamo, first author of the study.

So, even though there may be fewer types of birds, the ones that remain or thrive in cities bring a wide range of colors with them. This makes the visual landscape of urban birdlife surprisingly rich.

City life changes how birds evolve

This study offers more than just colourful observations. It highlights a deeper reality — cities can influence the course of evolution. Traits that were once neutral or even harmful may become beneficial in urban settings.

Birds with more vivid plumage now have an edge in places once considered unsuitable for wildlife. This shift affects not only how birds look but how they behave, reproduce, and interact with one another.

While this research focused on birds, it opens the door to a broader question: do other animals also change their appearance to cope with urban living? That remains to be explored.

What more can cities teach us?

Urban areas are expanding faster than ever. As we build more, we reshape ecosystems in ways we still don’t fully understand. This study provides one important piece of the puzzle. It shows that city life selects for color in birds, influencing not just which species survive, but how they look while doing so.

Future research will need to explore how widespread this pattern is. Does it apply only to birds? Or will we find similar patterns among insects, reptiles, or mammals?

For now, the message is clear. In the grey world of concrete and steel, color still matters – and in some cases, it matters even more.

The study is published in the journal Ecology Letters.

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