A new study has found that the red-necked nightjar is not just nocturnal but actually lives in direct harmony with the moon.
Following a decade of fieldwork in the Doñana National Park in south-west Spain, researchers have determined that key behaviours of the red-necked nightjar (Caprimulgus ruficollis), such as feeding, migrating and breeding, are dictated by available levels of moonlight.
Nightjars in the family Caprimulgidae are found throughout the world, and the red-necked is the largest species to be found in Europe. This species spends the winter in west Africa, before migrating to the Iberian Peninsula, Morrocco, and northern Algeria where they breed.
Unlike the reeling, insect-like churr of the more widespread European nightjar (Caprimulgus europaeus), the red-necked nightjar produces a tapping kjotek-kjotek call, similar to a car alarm. This is often the only evidence people might have as to the presence of a bird that spends daylight tucked up out of sight.
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The red-necked nightjar becomes active at dusk, when it hunts for flying insects, predominantly moths, on the wing. In order to understand better the bird’s habits, the research team has been tracking them during darkness by using a multi-sensor data logging system, developed at Lund University in southern Sweden. A total of 74 adult birds were fitted with trackers, 5 of which also carried Global Positioning System (GPS) loggers.
This enabled the team to monitor flight activity, migration movements and periods of torpor, before comparing the results to the lunar cycle and weather patterns.
“Unlike bats, the nightjar lacks the ability to navigate effectively in total darkness,” explained Anders Hedenström, professor of biology at Lund. “This is an animal that lives with small margins. Without moonlight, the energy balance simply doesn’t add up.”
The presence of a full moon enabled the nightjars to hunt throughout the night, building energy reserves to counter the darker, moonless nights when they could only feed at dawn and dusk. During periods of inactivity, the nightjars would conserve energy by lowering their body temperature, a strategy similar to hibernation which is rarely seen among birds. The team also found that nightjars would time their breeding so that eggs would hatch during periods of high insect activity.
“The next step is to understand how artificial light affects these systems,” Hedenström added, “If we alter the night-time light, we risk disrupting their entire life cycle. This knowledge is vital when it comes to implementing conservation measures.”
Top image: m-martinez/Getty Images
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