It might be just a juvenile, but this black-headed heron sure knows how to partake in a finch feast.

These amazing photographs, captured back in 2014 by Corlette Wessels of African Photography, come our way from southern Africa's Kgalagadi Transfrontier Park. "The heron would walk around the dam making himself smaller and holding himself lower than usual," recalls Wessels. "As the finches came to drink, [the heron] would grab them."

After dunking its fluttering prey in the water (nobody likes dry finch), the heron would throw back its head and swallow the birds alive. According to Wessels, it managed to vacuum up at least four over the course of an hour before flying off.

The behaviour might seem grisly, but black-headed herons regularly dine on their winged compadres and can swallow anything up to the size of a ruff (a wading bird that stands about 20-30 centimetres tall).

"This is completely in keeping with normal behaviour for the species," explains Dr Susan Cunningham, a researcher at the Percy Fitzpatrick Institute of African Ornithology. Modern birds don't have any teeth, so most species swallow their food whole. In the case of herons, scoffing down even fairly large prey is done without difficulty.

As for the water-dipping routine before swallowing, Cunningham explains that the heron may have been "trying to subdue [the finches] so they were less likely to escape during the swallowing process, but dampening the feathers to make them easier to swallow also seems plausible."

Widespread across much of southern Africa, black-headed herons are accomplished hunters that forage for everything from insects to small mammals. "We see black-headed herons regularly in the Kgalagadi – normally near water points, like this bird," says Cunningham. "However, this species is very adept at foraging in terrestrial environments and it is not as tied to water as many other heron species."

As for the small birds on the receiving end of the heron's attack, the scaly-feathered finches are arid savannah specialists common across the Kgalagadi. They typically forage on the ground and supplement their seed diet with the occasional insect. It's not unusual to see large flocks congregating at waterholes in this arid part of the world. Easy pickings for a hungry heron …