The Savanna Nightjar (Caprimulgus affinis) is a species of nightjar found in South and South-east Asia. Its preferred habitat are scrub, open country and particularly grassland with open stony patches.
Unknown to most, it is actually a recent resident species of Singapore. It is believed to have colonised Singapore through the Riau Archipelago in Indonesia, and spread to Singapore and Malaysia subsequently from the 1980s onwards. What is surprising about this fact is that the species is not known to be a strong flier nor is it a migratory one. So perhaps what one can say about birds in strange places is that one should not jump to conclusion about their origin!
The bird is largely nocturnal and hunts for insects at night, usually solitary but sometimes in a small group. They are very vocal in flight, and that one of the way to find them.
(In flight during daytime after being flushed, showing the body and under-wings. The bird normally doesn’t fly far after being flushed, often preferring to do fly low, with a few banking action to confuse the observer and land less than 50 meters from its original position.)
(At rest on a hot day in Tuas Grassland. The stony patches with surrounding scrub or grass are its favourite habitat and the bird blends well with the environment. In the video provided below, the action to keep cool is shown more clearly.)
A video of a nightjar in Tuas using gular fluttering to cool itself down on a hot sunny day. Because the nightjar mostly stays stationary during the daytime in the open for extended period of time, it has to thermoregulate itself better than birds that move into shaded area in the hot sun. Notice the open mouth. The rate of blood flow around the mouth area is increased, and the moist gular area rapidly vibrates.
The Avifauna of Singapore (K.S. Lim, 2009)
Gular Fluttering on AskNature website