A male Eurasian bittern (Botaurus stellaris) 'booms' from a relatively open position amongst the reedbeds.
This clip was filmed on an #iPhoneXs around fifteen minutes before sunrise at RSPB Otmoor nature reserve, Oxfordshire, UK, using the phonescoping technique. I was filming a pair of bitterns in the distance when I caught sight of this male sitting around 95m from my position. Luckily he stayed in sight for a little while, during which he boomed shortly after a brief threat display - the threat display presumably to something overhead or nearby which I didn't spot.
The actual conditions were quite a bit darker than it appears here; the necessary high-ISO filming resulting in quite a lot of video 'noise' and lack of fine detail in the original file. There's also some 'heat haze' contributing to a slightly wobbly image, even though the sun hadn't yet appeared over the horizon.
Shooting at such a distance meant that the boom call ended up being around a third of a second behind the image in the original clip, so the audio has been adjusted in the edit to bring it back into sync.
