Fishing With Green-backed Herons

The Green-backed Heron is a bird with an extraordinary talent: fishing for its food using bait. Located in areas around the world such as the USA, Africa, and more specifically, Kyushu in Japan, both adult and juvenile birds have been observed using a variety of baits to catch fish in ponds.

Images: Photographer Chris Mazzarella

A Japanese scientist, H. Higuchi, spent approximately 60 hours over the months of June, July and August, observing the herons around a pond in Kyushu, Japan. The types of bait used by the herons included flies, adult insects, insect larvae, earthworms, twigs, leaves, berries and other plant material. Feathers were also seen being used. The Japanese herons were seen using a wide variety of bait, whereas in the United States, birds more specifically used bread, fish pellets, mayflies and feathers. Bait availability was found to be subject to the time of the year.

As shown below, flies were the most successful form of bait used by both adults and juveniles, however, adults had a wider range of success using the different types of bait, whereas the juveniles were successful only with flies. Many attempts were documented of juveniles using twigs and leaves, but to no avail.

Image: Journal Article: Bait-fishing by the Green-backed Heron Ardeola striata in Japan

The heron’s technique of fishing involved collecting the bait when they arrived onsite at their feeding ground, and watching for prey from the side of the pond. The birds would then throw their bait in the water, and crouch down, supposedly to avoid being spotted by their prey. As their prey would approach the bait on the surface, the herons rushed forward to the fish and collected their meal.

Adult herons that chose bait in the form of twigs were seen holding down longer twigs under their feet, and snapping off pieces with their beak to make smaller and more tantalising lures.

There were a few issues with the overall fishing technique, and it was seen mostly in juveniles who were still struggling to perfect it. Two main problems were commonly seen

1.  Juveniles would throw the bait in the water, and forget to crouch down, giving away their ambush position to their prey
2.  When juveniles used twigs, feathers and leaves, they were not broken down into small enough pieces and were not of interest to the fish.

Due to their inexperience, it was not uncommon for the frustrated juveniles to resort to eating their selected insect baits after being repeatedly unsuccessful in their fishing attempts.

Fishing with the use of bait is not the primary method of feeding in Green-backed Herons, as they have been seen simply ambushing fish without the use of any lures of any kind. This adaptation to the use of baits may have evolved behaviorally due to an easier method of finding food, whereby the prey approaches the predator, as opposed to the predator seeking the prey. It is a more energy efficient method, and as stated in Higuchi's (1986) paper, 85.7% of the observed birds were successful using flies as bait.

A video published by Youtube user "TINKERPOPPYIMBA" shows an adult Green-backed Heron fishing (with success!) using a piece of bread.

Reference:

HIGUCHI, H. (1986), Bait-fishing by the Green-backed Heron Ardeola striata in Japan. Ibis, 128: 285–290. doi: 10.1111/j.1474-919X.1986.tb02677.x