Chickens blush: French study unveils emotional signals through skin colour

French scientists from the National Research Institute for Agriculture, Food, and Environment (l’Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement—INRAE) have discovered that the emotions of domestic chickens can be discerned from the colour of their skin. Their research, published by the Public Library of Science PLOS, showed that birds, like humans and other animals, can blush.

Scientists have studied animal facial expressions for many years to understand their emotions better. Previous research primarily focused on mammals, such as various species of primates (including humans), dogs, cats, horses, pigs, and mice. Birds, particularly those bred for agriculture, were typically overlooked in analyses.

Hence, the French scientists decided to study how domestic chickens express their emotions through the colour of their skin and the position of feathers on their heads. They conducted research on two breeds of ornamental domestic chickens: the bantam Cochin and the Meusienne. Ethologists observed 18 hens, exclusively females, aged between 2 and 3 months, reared free-range on two farms in the Loire Valley.

The research lasted about four weeks. Before starting the main phase of the study, which involved filming the animals' reactions to various stimuli, researchers spent several days with some of the chickens to get them accustomed to the presence of people and cameras. Each hen was tested twice and filmed from different angles using two cameras.

Scientists were interested in the behaviour and appearance of the birds in various situations: during rest, eating a favourite food, sand bathing, as well as in alert and fear situations, for example, in response to the presence of a predator in the sky, barking dogs, car or aeroplane noise, or the sounds of other birds. They also recorded how chickens behave when a human grabs and holds them.

The study's authors categorised emotions related to different situations as positive (when the birds bathe in sand or receive mealworm larvae) and negative (when they feel threatened). It turned out that the most noticeable chicken reactions occurred in unpleasant situations – the skin on their combs, featherless cheeks, and wattles turned deeply red. Researchers observed that the chickens' faces blush slightly less when they experience pleasure.

"Although our findings are preliminary due to a small sample size they hint that less redness in the cheek and ear lobes may indicate calm and contentment states," said Delphine Soulet from INRAE, the study's lead author.

She added that more pronounced red skin on the chickens indicates higher emotional arousal, including excitement at the sight of favourite food or due to a threat. The birds also blushed when a human appeared in their environment – whether bringing mealworm larvae or trying to catch them. However, when the animals had become accustomed to the presence of humans, they blushed less.

Scientists also discovered that chickens signal their emotional states with the feathers on their heads. This phenomenon was previously noted in some species of parrots and red-vented bulbuls (Pycnonotus cafer). Observations indicate that birds fluff the feathers on their heads when they feel positive emotions and flatten them when they are scared.

"The authors seem to have discovered some, especially with the feather fluffing, which I think would be easy for animal care staff or farmers to observe and identify as something that could suggest their birds were content," the French researchers wrote in their conclusion.