When observing birds, one might occasionally see them lying on the ground with their wings extended. This seemingly unusual posture is a deliberate set of behaviors that serve various important functions for the bird’s health. The reasons behind this wing-spreading can range from maintaining body temperature to intricate self-care practices.
Basking for Warmth and Wellness
Birds frequently engage in sunbathing, or “basking,” by lying down and spreading their wings to absorb solar energy. This behavior is common after chilly nights or during periods of cooler weather, as it aids in thermoregulation, helping birds warm their bodies efficiently. By spreading their wings, they maximize the surface area exposed to the sun, allowing for quicker absorption of heat.
Sunbathing also plays a role in feather maintenance and overall health. The warmth from the sun can help dry feathers, especially after rain or a bath. Furthermore, exposure to ultraviolet (UV) light during basking is important for vitamin D3 synthesis in birds. This vitamin is essential for calcium absorption, which contributes to strong bones and healthy feathers. Some theories suggest that sunning may also help control ectoparasites by dislodging them or making them more vulnerable to preening.
Feather and Skin Maintenance
Beyond temperature regulation, birds spread their wings while lying down for feather and skin care. Dust bathing is a common behavior where birds create a shallow depression in dry, fine soil, then vigorously wriggle their bodies and flap their wings. This action disperses dust throughout their plumage, helping to remove excess oils, dead skin, and external parasites. The dust absorbs these substances, and the bird shakes it off, leaving its feathers cleaner and in better condition for insulation and flight.
Another maintenance behavior is “anting,” where birds allow ants to crawl over their feathers or actively rub ants onto themselves. During passive anting, a bird might lie on an anthill with wings spread, letting ants explore its plumage. Active anting involves the bird picking up ants in its beak and applying them to its feathers. Ants produce chemicals like formic acid, which may act as a natural insecticide or fungicide, helping birds deter or eliminate feather mites and lice.
Survival Instincts and Practical Needs
In addition to self-care, birds may lie down and spread their wings as a survival tactic. The “broken wing display” is a deceptive behavior used by ground-nesting birds to protect their nests or young from predators. The parent bird feigns injury, dragging one or both wings and appearing to struggle, to distract a threat. This display lures the predator away from vulnerable offspring; once a safe distance is achieved, the bird “recovers” and flies away. This behavior is documented across bird families, including shorebirds, waterfowl, and doves.
Aquatic birds also utilize a spread-wing posture to dry their feathers after being in water. Birds like cormorants and anhingas, with less waterproof plumage, perch with their wings extended to air-dry. This allows their feathers to shed water, enabling efficient flight and buoyancy. While often done standing, maximizing surface area for drying can involve a more reclined position.