08-17-2023

Great tits often lose their vivid colors in the city

Earth.com staff writer

Urbanization is accelerating all around the globe, fundamentally transforming natural landscapes and presenting a vast variety of animals that are forced to live in cities and towns with new challenges.

Although some animals may benefit from milder temperatures and the presence of fewer natural predators, they also need to find ways of coping with increased pollutants and changes in their diets.

Paler plumage

Previous research has shown that urban-dwelling animals have duller coloration compared to their non-urban counterparts (the so-called “urban dullness” phenomenon).

However, while these studies have largely focused on single geographic locations, a team of scientists led by Lund University in Sweden has now investigated this phenomenon across the entire Europe, by taking as a case study a common songbird, the great tit (Parus major).

Using feather samples collected from great tits in cities and forests across Europe, the experts have found that urban great tits are indeed paler than their forest-dwelling counterparts.

Lack of carotenoids

The typical yellow color in the great tit’s feathers is caused by carotenoids, a class of pigments that the birds get from the insects they eat. These insects, in turn, get these nutrients from the plants they consume.

Since carotenoids are important antioxidants which help the body mitigate the toxic effects of pollutants, if urban great tits cannot obtain sufficient carotenoids from their food, their plumage becomes paler, resulting in weaker resistance to the adverse effects of pollution.

“Our findings suggest that birds in the city are not getting the right diet. This can help us understand how to create urban environments that are more beneficial for biodiversity. By planting more native trees and plants in our gardens and parks we can help small birds, such as great tits, by providing them with a healthy diet of insects and spiders for themselves and their chicks,” said study senior author Hannah Watson, a biologist at Lund.

Surprisingly though, the analysis revealed that the effects of cities on birds’ coloration vary across the European continent. For instance, while in Lisbon, forest great tits displayed much brighter feathers than urban great tits, in Malmö, the difference in plumage between city and forest tits was considerably smaller.

Urban dullness

“Overall, our results provide evidence for uniformity in the ‘urban dullness’ phenomenon but also highlight that the magnitude of the effect on coloration depends on local urban characteristics,” the authors explained.

“We need further research to understand why some cities have more favorable environments for birds and wildlife than others. This can help urban planners develop biodiversity-friendly policies and improve the quality of life for people living in cities,” Watson concluded.

The study is published in the Journal of Animal Ecology.

More about great tits

The great tit (Parus major) is a passerine bird in the tit family Paridae. It’s a common and easily recognizable bird found across Europe, Central Asia, and parts of North Africa.

The great tit is known for its vibrant coloration, mainly yellow with a black stripe down the breast and black head. It’s a medium-sized bird, typically weighing between 14 to 18 grams and measuring around 12.5 to 14 cm in length.

Their diet mainly consists of insects, seeds, and nuts, and they are often found in woodlands, gardens, and parks. Great tits nest in tree holes or nest boxes and typically lay between 5-12 eggs. The female incubates the eggs, and both parents help feed the chicks.

Known for their curiosity and intelligence, they have been observed using tools and solving problems to obtain food. Their song is a familiar sound in many parts of their range and is composed of several repeated notes.

The great tit is not currently considered endangered, although changes in habitat due to human activity may affect local populations.

Other aspects of urban dullness

Urban dullness refers to the monotony or lack of variety and excitement in urban environments. It can manifest in various ways:

Architectural monotony

Repetitive building designs, lack of color, and lack of architectural variety can make cityscapes seem bland.

Lack of green spaces

A shortage of parks, trees, and gardens can result in a concrete jungle effect, where nature is sparse.

Routine lifestyle

Living in a city can sometimes become routine – wake up, commute, work, commute, sleep. This daily grind can feel monotonous for many.

Overcrowding

High population densities without adequate infrastructure or recreational spaces can contribute to a sense of congestion and monotony.

Lack of cultural activities

While many urban areas are rich in culture, if these activities or places aren’t readily accessible or promoted, it can add to the feeling of dullness.