Скачать или смотреть Gular Flutter by Pond-Heron species (Ardeola sp.)

Gular Flutter by Pond-Heron species (Ardeola sp.)
I have often observed egrets, herons and other birds performing a gular flutter when the weather is hot. Gular fluttering is used as a means to regulate temperature. In gular fluttering, birds will often partially open the beak and flutter the upper throat muscles (moist gular region). The activity is rapid and does not involve large movements of the thorax (like when we pant) – an energy efficient cooling mechanism by evaporation.

I measured the gular flutter rate in this Pond-Heron species using video software to slow down the action. I did multiple counts and the highest rate was 332 per minute; note that the rate varied as I watched. I observed the bird at 1000 hrs and this was not the peak heat time. I suspect the gular flutter rate will be even higher at noon. A short video recording of the gular flutter is available here. The bird is in Basic (non-breeding) plumage hence the exact species is not possible to determine.

Maclean (Ecophysiology of Desert Birds, Springer Science, 2013) mentions that the 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 have measured gular flutter rates of 600-720 times per minute in Grey Heron (Ardea cinerea) and 745 per minute in the Large-tailed Nightjar (Caprimulgus macrurus).

Amar
(Dato' Dr Amar-Singh HSS)
Ipoh, Perak, Malaysia