Scientists discover colorful birds can thrive in cities

By Stephen Beech

Colorful birds thrive in cities, according to new research.

Avian species that do well in urban areas have feathers of a more vibrant color and are less brown, say scientists.

They explained that the ongoing, worldwide increase in urbanization is considered one of the main causes of the steady decline in biodiversity.

Urban ecology is the field of research that focuses on the effects of urbanization on different organisms.

Previous studies have looked at how urban noise affects communication in birds.

But, until now, little was known about the relationship between urbanization and birds' plumage color.

Study leader Professor Bart Kempenaers, of the Max Planck Institute for Biological Intelligence in Germany, explained that plumage color serves many important functions.

He said that it can play a role in keeping an animal warm or avoid overheating, in camouflage, in competitive interactions, or in mate choice.

But cities tend to be warmer, have fewer predators, more artificial light and novel background colors like that of concrete and asphalt.

Dr. Kempenaers said it is therefore "quite conceivable" that the urban environment can affect the color of animals.

The Max Planck Institute researchers, together with colleagues from the University of Granada in Spain, wanted to get to the bottom of this issue.

The team used a global dataset on the abundance of more than 1,200 bird species in habitats with different levels of urbanization and combined it with data on plumage color.

They then analyzed the extent to which plumage color could predict the relative abundance of the species in urban areas.

The findings, published in the journal Ecology Letters, showed that species that thrive in urban areas are less brown.

Study co-lead author Dr. Kaspar Delhey said: "Brown shades are more common in natural environments than in cities.

"We suspect that brown birds are at a disadvantage in a rather gray city.

"The predominant colors of a city and the lack of suitable habitats can therefore determine which bird species are successful there."

The study also showed that successful urban bird species have more elaborate colors in their plumage, which is especially true for females.

Cities seem to favor more colorful birds – probably because there are fewer predators in urban areas and "being seen" poses a lower risk than in rural areas, according to the research team.

Previous studies suggested that color diversity is lower in urban bird communities, but the team showed that the opposite is true.

Study first author, University of Granada Professor Juan Diego Ibáñez-Álamo said: "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."

He added: "The study clearly shows that successful urban birds differ in color from those that fail to thrive in the city – urbanization and bird coloration are therefore linked.

"Future research will need to show whether this also holds true for other animal groups."