Wing Colour of Common Gulls reflects Their Longevity

Doctoral student Richard Meitern demonstrates the wing pattern of a gull that was researched. Photo: Tuul Sepp
Doctoral student Richard Meitern demonstrates the wing pattern of a gull that was researched. Photo: Tuul Sepp

The appreciation of beauty is highly evolved among birds. The incredible variety of bird plumage coloration is mainly the result of birds choosing the prettiest among them for mating partners. A pretty bird is a bird with good health, so by picking a beautiful mate, a bird also gets good genes for its offspring. Thus, pretty feathers show health.

But do they also predict the longevity of birds? This question is especially important for long-lived monogamous species with persistent partnerships for taking care of their young together according to Tuul Sepp, a post-doctoral researcher at Arizona State University and researcher at the Institute of Ecology and Earth Sciences, University of Tartu.

“Can birds count on a long row of happy anniversaries by choosing a mate with pretty feathers?” was the question posed by Sepp. To find an answer for this question, Sepp and Kalev Rattiste, researcher at the Department of Zoology, Estonian University of Life Sciences, studied whether the black and white wing pattern of long-lived monogamous seabirds—common gulls—, predicts the future lifespan of the birds.

Doctoral student Janek Urvik and Hüüp Sepp ring nestlings. Photo: Tuul Sepp

Doctoral student Janek Urvik and Hüüp Sepp ring nestlings. Photo: Tuul Sepp

Gulls have Similarities with Humans

Sepp and Rattiste found that birds with better genetic characteristics that lived longer had more white and less black feathers on their wings. “The wing pattern was mostly similar throughout the birds’ life, which is amazing since, as we know, birds change their feathers every year,” Sepp explained. She added that as the birds got older and their health deteriorated, they started getting more black and less white feathers on their wings. “This was true for both males and females. This indicates that if both parents are choosy about their partner and invest in offspring care (as it is in humans!), the traits that are viewed as beautiful evolve in both sexes,“ Sepp noted.

Sepp said that this research and its results offer the possibility to view gulls as a model system for understanding the evolution of beauty in all other long-lived monogamous species. “This is something that interests evolutionary biologists even more than specific knowledge about one species,” she said. Sepp added that a better understanding of gull behaviour and its similarities to human behaviour helps people to appreciate these birds more. “Therefore, these kinds of studies, and especially public outreach based on these studies, help to protect species that are sometimes viewed as a nuisance, as gulls sometimes seem to be,” Sepp mentioned.

Rattiste told that common gulls (Larus canus) have been studied in Estonia since 1962. “They provide good material for research—the birds are not so sensitive, live in colonies, are loyal to birth and nesting sites,” he explained. For example, the research group marked a gull named Marta in 1981 just after hatching. Now they have met already more than 15 descendants of Marta who all breed in the same colony.

Gulls are not afraid of the moving hide that is used to collect information about them. Photo: Tuul Sepp

Gulls are not afraid of the moving hide that is used to collect information about them. Photo: Tuul Sepp

Gulls offer Many Topics for Research

Until the 1980s the main focus of gull studies was on demographic indicators, later genetic aspects were studied, while today different sides of eco-physiology are being explored. Rattiste mentioned that data collected about birds over such a long time period is unique in the world and it has widened the knowledge about the reproduction strategies of this long-lived bird species to a great extent.

In the future Sepp, Rattiste and their research groups plan to study how much parasites affect the wing pattern of gulls. Sepp said that they already know white feathers are more prone to abrasion and damage from feather-eating bacteria and insects. “Therefore, only birds without parasites could allow large white plumage spots,” she explained.

They also plan to study the similarities between the wing patterns of partners—do prettier females choose prettier males and vice versa, and do these partnerships last longer? These are some of the questions that PhD student Janek Urvik is looking into now.

This article was funded by the European Regional Development Fund through Estonian Research Council.