Great Tits in the City: Urban Environments Influence Feather Color

Great tits are small songbirds that are widely distributed across Europe and Asia. They are known for their striking yellow breast feathers and distinctive song, which make them a common sight in gardens and countryside alike.

However, not all great tits are equally colorful, as new research has revealed that some great tits may have paler plumage than others, depending on where they live.

The latest study, led by researchers at Lund University, Sweden, and the University of Glasgow, analyzed feather samples from great tits in cities and forests around Europe.

The researchers found that urban great tits are often noticeably paler than their countryside relatives, with dietary differences thought to be the main cause.

Why does plumage color matter?

(Photo : PATRICK PLEUL/DPA/AFP via Getty Images)

Plumage color plays a number of significant roles in bird health and behavior. Coloration can influence mating selection, as birds may prefer mates with brighter or more attractive feathers.

Coloration can also affect predation risk, as birds may use their feathers to blend in with their surroundings or to signal their unpalatability to predators.

Moreover, coloration can reflect the physiological condition and immune status of birds, as feathers are made of keratin, a protein that requires energy and nutrients to produce.

One of the main factors that determines the color of bird feathers is the presence of pigments, such as melanins and carotenoids.

Melanins are produced by the birds themselves and provide colors ranging from black to brown to gray, while carotenoids are obtained from the diet and provide colors ranging from yellow to orange to red.

The latter is particularly important for great tits, as it gives them their distinctive yellow breast feathers.

However, carotenoids are not only used for coloring feathers, but also for other vital functions in the body.

Carotenoids are antioxidants that help protect the cells from oxidative stress caused by free radicals, which can damage DNA and proteins.

Oxidative stress can be induced by various factors, such as pollution, infection, or inflammation.

Carotenoids can also modulate the immune system and enhance the resistance to pathogens. Therefore, carotenoids are a limited resource that birds have to allocate between different competing demands.

Also Read: Urban Great Tits Are More Stressed Than Their Countryside Counterparts [Study]

How do urban environments affect plumage color?

Urban environments pose many challenges and opportunities for birds.

On one hand, urban areas offer milder temperatures, artificial lighting, and abundant food sources, such as bird feeders or human waste.

On the other hand, urban areas also entail higher levels of noise, pollution, and disturbance, as well as reduced habitat quality and diversity.

These environmental changes can affect the availability and quality of carotenoids for urban birds. For example, urban areas may have fewer plants that produce carotenoids or fewer insects that feed on them.

Urban areas may also have more pollutants that degrade carotenoids or increase their demand due to higher oxidative stress.

To investigate how urban environments affect plumage color in great tits, the researchers collected feather samples from 160 adult male great tits in 16 cities and 16 forests across Europe.

They measured the reflectance of the feathers using a spectrophotometer and calculated the brightness and chroma (saturation) of the yellow color.

They also analyzed the carotenoid content of the feathers using high-performance liquid chromatography.

The results showed that urban great tits had significantly paler plumage than forest great tits, both in terms of brightness and chroma.

Urban great tits also had lower carotenoid levels in their feathers than forest great tits.

These differences were consistent across different regions and seasons.

The researchers suggested that the paler plumage of urban great tits indicates that they have lower dietary intake of carotenoids or higher allocation of carotenoids to other functions than feather coloration.

They also speculated that urban great tits may face lower selection pressure for bright plumage due to reduced predation risk or altered mate preferences in cities.