Gular flutter of Large-tailed Nightjar

“Our ‘resident’ male Large-tailed Nightjar (Caprimulgus macrurus bimaculatus) has been with us for more than 4 weeks and my wife has affectionately named him ‘Clockwork’ in line with his fixed routines. It has been wonderful to show this bird to ‘non-birdwatching’ visitors who visit our home; all have been amazed that such birds exist (more budding bird watchers in the making). We have now extensive observations and would like to share a few.

“Gular fluttering by nightjars as a means to regulate temperature is well known. This is however my first personal observation of this behaviour. Fowler and Miller, 2003, say ‘Nightjars dissipate heat by gular fluttering, during which the mouth is opened, the rate of blood flow to the buccal area is increased, and the moist gular area is rapidly vibrated.’

“Susie Cunningham 2016 (Nightjar superstars! Hot Birds Research Project – The study of desert birds under climate change LINK says ‘Gular fluttering consists of rapid movements of the gular region (i.e., throat). The advantage of gular fluttering over panting is that it does not involve the large movements of the thorax that is characteristic of panting. …when gular fluttering, nightjars can dissipate large heat loads without expending lots of energy. Thus, gular fluttering is typically regarded as an ‘energetically efficient’ evaporative cooling mechanism.’

“Gordon L. Maclean 2013 (Ecophysiology of Desert Birds. Springer Science & Business Media) offered rates of this activity. Respiratory rate when panting may rise to 200 movements/min but gular flutter may occur at excess of 400-600 movements/min. When gular flutter is independent of the rate of respiratory movements, then it can occur in excess of 900 times/min.

“I was able to video a gular flutter episode at lunch time on a particularly hot day. The bird had assumed an ‘odd’ posture spread out on the ground with feather splayed (see posts and video). I used a number of video software tools to play the video is slow motion to determine the flutter rate. The peak gular flutter rate was 745 per minute which is in line with Maclean’s data. As paediatrician I am used to such fast rates of ‘ventilation’. At work we use high frequency oscillatory ventilation (HFOV) – a type of mechanical ventilation that uses vibration for air flow in very premature neonates at very high rates of up to 900/minute.

“Video above. Apologise for background voices. I found that editing the video in the usual way damaged the rate of the gular flutter in the output video (slowed it down). So I have uploaded a raw video.”

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
6th June – 5th July 2017

Location: Ipoh, Perak, Malaysia
Habitat: Wild urban garden