Adult chicken hens express their affective states via bare facial skin blushing and head feather movements (2025)

Soulet, D., Love, S. A., Blache, M.-C. et al.

Abstract

In mammals, facial expressions serve as a window into a variety of affective states. Emotional facial expressions in birds have received little scientific attention. Juvenile hens showed variations in their facial display, facial redness and head feather position, depending on their affective states. When sexually mature, domestic hens develop fleshy coloured outgrowths such as the comb and the wattles, which are considered as functional visual signals of the individual’s health or fertility. Here, we investigated, in adult hens, whether bare facial skin (cheeks, ear lobes, comb and wattles) redness and head feather position (sleeked/fluffed) also vary with affective states. We hypothesized little or no redness variations for the wattles and comb because of their involvement as functional signals. Twelve adult hens were filmed during naturally occurring situations and controlled tests varying in their valence and arousal level: situations associated with fear/frustration (negative valence/high arousal), situations associated with appetitive motivational states (positive valence/high arousal) and situations associated with calm/contentment (positive valence/low arousal). We showed that positive situations of low arousal were associated with the lowest redness in all areas of bare skin. A significantly higher level of redness was found in high arousal compared with low arousal positive situations, except for the comb. The highest redness was observed in all skin areas in negative situations of high arousal. Head feathers were observed more frequently fluffed in most of the positive situations and sleeked in all feed-related situations. Thus, facial skin redness, including secondary sexual characters and head feather position are potential markers of the affective states of adult hens. Studying facial displays opens new research opportunities to increase our knowledge on how avian species perceive their environment. Further research is needed to clearly differentiate between the effects of valence and arousal.