“The Striated Heron (Butorides striatus) is not picky in its food. Big fish or small fry – both can become its meal. It does not mind the extreme sizes of its catch and will eat whatever is available.
“A sequence of pictures captured the process of a Striated Heron swallowing a big fish that has a wider body than the bird’s head (above, below). It is a real wonder that its throat can expand so much to consume the fish complete with spiny fins. It stretched and straightened its neck to stay upright to help ease the fish down its throat. Amazingly, it took less than 2 minutes to swallow the big fish (for comparison, I have seen the physically larger Grey Heron (Ardea cinerea) consuming a similar-sized fish in about 20 minutes).
“After the heavy dinner, the bird looked sluggish with a huge bulging belly. For a brief period, it felt so heavy that it changed to a sitting posture to rest (below left). It puffed up and shook itself to get rid of its lethargy. It then proceeded to drink a few times – perhaps aiding digestion (below right). There is no further observation as I had to leave for another appointment.
“On the left is another Striated Heron taking a small fry, which looked so tiny that you can barely see it in its bill. In the field, the bird was seen stalking and plunging its bill into the shallow water. It was only later, while checking full screen images, that I realised that there was a tiny fry in its bill. The bird must have excellent vision coupled with pin-point accuracy to be able to pick out this tiny fry from underwater!”
Kwong Wai Chong
4th December 2009
Note: The fish is always swallowed head first, so that the spines do not damage the oesophagus that can easily be expanded to cater for its large size. From here the fish enters the upper part of the stomach, the proventriculus, which is also expandable. Here, secretions from gastric glands that include hydrochloric acid, break down the proteins in the fish as well as dissolve some of the bones. The lower part of the stomach is the muscular gizzard that grinds the fish up as well as compact the remaining bones into a pellet. If Wai Chong was to remain and kept the heron in his sight, he could have observed the bird casting a pellet after a short interval.