Cormorants, aquatic birds, are often observed in a distinctive posture: standing upright with their wings spread wide, resembling a crucifix. This behavior is a common sight in coastal and inland waters where these birds reside. While seemingly a simple action, this unique stance serves several important purposes for the cormorant, allowing them to thrive in their aquatic environments.
Drying Their Feathers
The most significant reason cormorants spread their wings is to dry their plumage. Unlike many other waterbirds, such as ducks, cormorant feathers are not fully waterproof. Their feathers have a unique microscopic structure that allows water to penetrate, reducing their buoyancy to dive deep underwater in pursuit of fish. This adaptation, while beneficial for diving, means their feathers become waterlogged after prolonged immersion.
To counteract this, cormorants must regularly dry their feathers to maintain their insulating properties and enable flight. By spreading their wings, they expose the wet feathers to air and sunlight, facilitating evaporation. Observations show that cormorants engage in this open-wing posture almost exclusively after having been in the water, and the duration of the behavior is often linked to how long they were submerged. Drying is the primary function of this characteristic stance.
Regulating Body Temperature and Aiding Digestion
Beyond feather drying, wing-spreading may also play a role in regulating a cormorant’s body temperature. After dives in cool water, spreading their dark feathers allows them to absorb solar heat, helping them warm up. This basking behavior can contribute to maintaining their metabolic rate, particularly in colder conditions.
While less understood, some theories have explored whether wing-spreading aids digestion. However, research indicates that the behavior is not primarily for this purpose. Studies have shown that wing-spreading occurs regardless of whether a bird has successfully caught prey, suggesting it is not directly linked to the digestion of food.
Dispelling Common Misconceptions
The wing-spreading posture is frequently misinterpreted as a social display. However, this distinctive stance is not for purposes of courtship, aggression, or territorial display. While cormorants, like many bird species, do engage in various courtship rituals, their wing-spreading behavior is fundamentally functional.
Evidence supports the practical benefits of drying and, to a lesser extent, thermoregulation. The behavior is a direct consequence of their specialized feather structure, which is optimized for diving rather than water repellency. This functional explanation differentiates cormorants from other birds that might use similar postures for social signaling.