Sunday, March 9, 2014
By Herb Wilson
I’ve been grading midterm exams so learning is on my mind. A lot of learning goes on in the bird world, too.
The ability to sing has a strong component of learning in most birds. Although a bird raised in isolation will attempt to sing, its song will be a poor rendition of the song its father sang to attract its mother.
A number of birds are able mimics. A parrot can be taught to say “Polly want a cracker” and any number of other phrases. A northern mockingbird can mimic as many as 30 other species of birds. The marsh warbler in Britain mimics 99 European species and 133 African species that it coexists with on its wintering grounds.
A lyrebird in Australia over 19 years learned to imitate barnyard sounds, including pig squeals, a chain rattling, a cross-cut saw and a howling dog, along with most calls and songs of the local birds.
A crested lark in Germany learned the whistled commands given sheep dogs (“Run ahead,” “Fast,” “Halt” and “Come here”). When taped and played back to sheep dogs, these calls were obeyed by the dogs.
Birds learn to solve complex problems more readily than many mammals in laboratory experiments. One involved a 4-foot long board with a narrow slit in the middle. A test animal was placed on one side, and two bowls were placed on the other side of the slit, visible to the test animal. One bowl had food and the other was empty.
The test animal watched as one bowl was moved to the far left and one to the far right, both out of sight. The animal was then allowed to walk around to try to find the food. Dogs and crows quickly learn to go around the side nearest the food. Cats, rabbits and chickens never solved the problem.
Learning to count is difficult for most mammals. It took 21,000 trials to get a monkey to learn the difference between a two-note sound and a three-note sound. Birds easily learn the difference. Parakeets and ravens can count to seven.
Birds engage in insight learning, a complex mode of learning. A bird is able to learn by observation and imitation of others. Blue jays can learn to tell edible from inedible caterpillars by watching the reaction of other blue jays when they attempt to eat a caterpillar.
Another nice example is described for great tits (a relative of our chickadees) in England. In the 1950s great tits learned to tear the cardboard caps of milk bottles to drink the cream. This innovative behavior was quickly passed on to other members of the species. Milk companies had to replace the cardboard caps with stronger metal caps to keep the great tits out.
Young birds must learn how to capture food. Young terns, pelicans and herons miss the fish they are pursuing far more frequently than adults. In North Carolina, I observed a number of young northern gannets dead on the beach. One possible explanation is these birds were diving into shallow water and breaking their necks.
Some birds have devised ways to use tools to feed. The woodpecker finch of the Galapagos Islands uses a stick or cactus spine held in its bill to pry insects from crevices. Egyptian vultures have learned to crack ostrich eggs using stones. Green herons are clever fishers, using pieces of bread as fishing bait. A green heron will drop bread into still water and wait for fish to gather, which it then captures by spearing with its bill. If currents carry off the bait, the heron will retrieve the bait and use it again.
Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at firstname.lastname@example.org