The question of whether nightjars are truly nocturnal can be answered with a qualified yes, placing them among the world’s most unique birds to operate under the cover of darkness. The nightjar belongs to the family Caprimulgidae, a diverse group found on every continent except Antarctica, occupying a wide range of habitats from deserts to forests. These medium-sized birds are also known by evocative names like goatsuckers and nighthawks, which are New World species within the same family.
Nightjars are characterized by their long, pointed wings, short legs, and soft, cryptically patterned plumage. Their ability to silently navigate the night skies to catch flying insects defines their existence. While often labeled as nocturnal, the timing of their activity cycle is more accurately described by a combination of night-time and twilight behavior.
Activity: Nocturnal or Crepuscular?
The activity pattern of the nightjar family is best defined as a blend of nocturnal and crepuscular behavior. A strictly nocturnal creature is active only during the darkest hours, but many nightjar species exhibit strong crepuscular tendencies, meaning they are particularly active during the twilight periods of dusk and dawn. Their peak foraging often occurs right as the sun sets and again just before it rises, when the light is dim but still sufficient for visual hunting.
Foraging activity deep into the night is heavily influenced by the presence of moonlight, demonstrating their reliance on visual cues. Research shows that hunting frequency can more than double on clear, moonlit nights compared to dark, overcast periods. This reliance on ambient light means that, while they are capable of activity throughout the night, their most intensive hunting periods are aligned with the edges of the day, or when the moon provides sufficient illumination.
Physical Adaptations for Night Hunting
The nightjar’s ability to hunt effectively in low light is supported by a sophisticated suite of physical adaptations, particularly focused on sight and feeding. Their eyes are disproportionately large relative to their body size, maximizing the amount of light collected. A reflective layer called the tapetum lucidum is positioned behind the retina, which reflects light back through the sensory cells, effectively doubling the light-gathering capacity and making their eyes shine in torchlight.
The retina itself is highly specialized for night vision, containing a much higher density of rod cells than cone cells, which are responsible for detecting light and movement in dim conditions. This visual system allows them to spot the silhouettes of flying insects against the slightly lighter night sky. This visual prowess is paired with a unique mouth structure, featuring an enormous gape that can be opened wide to scoop insects directly from the air.
Stiff, sensitive rictal bristles surround the expansive mouth opening. These bristles resemble whiskers and are believed to function as a sensory net to help detect or funnel prey into the gaping mouth as the bird flies. The combination of powerful eyesight and a wide, bristle-fringed mouth makes them highly specialized aerial insectivores, catching prey like moths and beetles mid-flight.
Diurnal Habits and Camouflage
The other half of the nightjar’s 24-hour cycle is spent in complete stillness, relying on masterful camouflage for survival. During the day, they exhibit superb cryptic coloration, with their mottled grey, brown, and rufous plumage seamlessly blending with their surroundings. This pattern mimics bark, leaf litter, or the dry ground where they often roost.
To maximize this disguise, nightjars remain virtually motionless throughout the daylight hours. When roosting on a tree branch, they adopt the unusual habit of perching lengthwise along the limb rather than across it, which further breaks up their outline and makes them appear like a broken stub of wood. If disturbed, they will flatten themselves against the substrate, only flying at the last possible moment. This behavior is a necessary defense mechanism, protecting them from diurnal predators who might otherwise easily spot them.