Nightjars, belonging to the family Caprimulgidae, are nocturnal birds found across most of the world, absent only from Antarctica and some island groups. Their intricately patterned plumage allows them to blend almost perfectly into their surroundings during daylight hours, making them particularly elusive. This specialized camouflage complements their highly adapted feeding habits, suited to twilight and nighttime activity.
Primary Diet: Night-Flying Insects
Nightjars are primarily insectivorous. Their diet consists almost exclusively of night-flying insects, with moths and beetles forming the bulk. They also consume a variety of other nocturnal insects, including:
Mantises
Dragonflies
Cockroaches
Mosquitoes
Gnats
Winged ants
Caddisflies
Grasshoppers
While their diet is dominated by flying insects, nightjars have been observed picking glowworms directly off vegetation. Any consumption of plant material or non-flying invertebrates is typically accidental. To aid digestion, nightjars also consume grit.
Ingenious Hunting Strategies
Nightjars primarily capture insect prey through aerial foraging. They are adept at catching insects in flight, often exhibiting a “hawking” behavior where they sally out from a perch or engage in continuous flight. A distinctive physical adaptation for aerial hunting is their wide gape, or mouth, which can open broadly to engulf insects mid-air.
Surrounding their wide mouths are specialized whisker-like feathers known as rictal bristles. While their precise function is still a subject of study, these bristles are thought to protect the bird’s eyes from struggling insects, help funnel prey into the mouth, or provide tactile sensory input for navigating and detecting prey in low light. Nightjars also possess notably silent flight, aided by specialized feather structures that dampen sound, allowing them to approach prey undetected.
Their exceptional night vision is a significant advantage, supported by large eyes equipped with a reflective layer called the tapetum lucidum and a high density of rod cells. This visual acuity allows them to hunt by sight, often silhouetting their prey against the dim night sky. Nightjars are most active during twilight hours (dusk and dawn), when light conditions are optimal for detecting insects. They may also exploit artificial lights, which attract large concentrations of insects, providing opportunistic feeding grounds.
Dietary Adaptations and Variations
The diet of nightjars is influenced by various environmental factors, including their specific habitat and seasonal insect availability. As opportunistic feeders, they adapt their consumption based on the most abundant insect species. This flexibility allows them to thrive across diverse geographical areas by utilizing locally prevalent prey.
Their cryptic plumage provides camouflage and helps conserve energy during daytime resting. This energy conservation is important for their nocturnal hunting activities. The lunar cycle also plays a role in their feeding patterns, with nightjars often increasing foraging activity during periods of bright moonlight. Nightjars can travel several kilometers from resting or nesting sites to find suitable foraging areas.