Not so long ago, tool use was one of the defining criteria for humanity. Subsequent observations of non-human creatures using, and in a few cases making, tools have required that goalpost to be moved. Primates—chimps, organs, capuchin monkeys—have been caught in the act, as have bottle-nosed dolphins, tropical reef fish, and at least one species of octopus, the one that carries coconut shells around. Not to mention a handful of birds, among which the New Caledonian crow, a maker and user, is the most technically sophisticated. Then there’s the Galapagos woodpecker finch that employs twigs and spines to pry insect grubs out of tree trunks; the Egyptian vulture that smashes ostrich eggs with stones; and, if a fishing lure can be considered a tool (and why not?), the bait-fishing herons.
The best-documented bait-fisher is the North American green heron, a fairly common species in what’s left of California’s riparian habitats. A heron will drop bits of bread into a pond, wait until a fish approaches it, then uncoil its long neck and strike. Some use feathers, others mayflies. The behavior was first reported in 1958, from Lake Eola in Orlando, Florida.
A close relative, the striated heron of East Asia, has been studied by Japanese ornithologists. They report that the herons use bait most often in open water with no suitable perches nearby. Bait has included live insects, earthworms, twigs, leaves, berries, and plastic foam. The live bait technique had the highest success rate. One striated heron broke twigs into smaller pieces before tossing them into the water, a clear instance of tool-making. It’s a learned skill; adult herons did better than juveniles.
Now another heron species has joined the club, the ubiquitous black-crowned night heron. These midsized herons are known for their opportunistic feeding habits. I’ve seen people hand-feeding chicken parts to the night herons at Lake Merritt, a risky activity—those beaks are sharp. At least one learned to hang around the fish stores in Oakland’s Chinatown for scraps. They’ll also prey on young coots and other birds.
Baiting by black-crowns has been reported since the mid-1990s from California (the Heritage Ranch in Irvine), Louisiana (the Audubon Park Zoo in New Orleans), and most recently Hawai’i, where the species is the only native heron, locally known as auku’u. According to an article in the Hawai’i Audubon Society’s newsletter ‘Elepaio, golfers at a course on Kaua’i got into the habit of scattering seeds near a water hazard along the fairway of the 11th hole to attract red-crested cardinals, one of the islands’ many exotic birds. A night heron was seen to drop some of the seed into the water hazard, where it attracted small fish, probably tilapia, which the bird then caught and ate. When golfers provided bread, the herons readily adapted. Sometimes koi, too large to handle, got to the bread first. (Only in Hawai’i would you have koi and tilapia in the water hazards.)
Word of this novel behavior went out on the Hawai’i birders’ listserve, and one reader recalled a television report about a bait-fishing night heron on O’ahu, this one near a Roy’s Restaurant on the island’s west coast. The heron, nicknamed “Hank,” had been using bread provided by the employee’s of a golf course snack shop. The technique appears to have spread from that individual to several other night herons in the neighborhood. A heron in a Honolulu park presumably acquired the trick independently.
It’s hard not to read the ‘Elepaio account without thinking of the Japanese monkeys who learned to wash sweet potatoes. To my knowledge, no one has speculated about a “hundredth heron” phenomenon.
Sporadic bait-fishing has also been reported for great blue herons, snowy egrets, and several Old World heron species, as well as for kingfishers, kites, gulls, sunbitterns, and crows.
I have seen no local reports of bait-fishing night herons (or, for that matter, green herons.) The next time you visit Lake Merritt, though, you might want to consider bringing some day-old bread along for the sake of experiment.