The sight of a large bird with outstretched wings, often called a “buzzard,” is a common observation globally. In North America, this behavior is frequently seen in vultures, particularly the Turkey Vulture (Cathartes aura), known for its distinctive reddish, bare head. When these birds stand with their wings spread wide, it is known as the horaltic pose or spread-wing posture. This behavior is a notable adaptation, sparking curiosity about its purpose.
Warming Up
One primary reason buzzards spread their wings is for thermoregulation, specifically to absorb heat from the sun. As endothermic animals, birds generate their own body heat, but they also use behavioral strategies to regulate their temperature, especially after cooler nights. Turkey vultures, for instance, can intentionally lower their body temperature at night, a state known as shallow regulated hypothermia, which conserves energy.
To raise their body temperature quickly in the morning, buzzards maximize their surface area exposed to solar radiation by spreading their wings. Their dark plumage efficiently absorbs sunlight, converting it into heat. This warming process is important for optimal metabolic function, aiding in the digestion of carrion, and preparing their muscles for flight. Achieving sufficient warmth is important for vultures, as they rely heavily on soaring flight to locate food, making efficient flight a necessity.
Drying and Wing Care
Wing spreading also plays a significant role in drying feathers and maintaining wing hygiene. After exposure to rain, dew, or bathing, buzzards spread their wings to air-dry their plumage. This drying process is important because wet feathers become heavy and lose insulating properties, impeding flight and making the bird vulnerable to cold. Maintaining feather structure through drying is important for aerodynamic efficiency.
Beyond simple drying, exposure to sunlight through this posture also contributes to feather health by deterring external parasites such as mites and lice. The heat and ultraviolet radiation from the sun create an environment less hospitable for these pests. This practice, sometimes referred to as “sunbathing,” helps sanitize their plumage, which is particularly relevant given their diet of carrion.
Subtle Signals
While thermoregulation and feather maintenance are the primary drivers of wing spreading, this behavior may also serve social or communicative functions. A buzzard’s spread-wing posture might signal to other individuals, such as asserting dominance at a feeding site or acting as a territorial display. However, these social aspects are secondary to the physiological benefits of warming and drying. The exact extent and frequency of these communicative displays in buzzards require further research.