Food, Learning, Memory

Michael Dvorak

Woodpecker Finches have a talent for tool use - they pry insects out of holes using modified twigs or cactus spines. New research shows that, when young, these Gal‡pagos birds can learn the technique by trial and error, even without observing other Woodpecker Finches using tools. In dry habitats, where the birds' prey are found underneath bark, 95 percent of Woodpecker Finches use tools. In humid areas where the finches capture insects in moss and on leaves, tool use is rare.

Experiments showed that juvenile Woodpecker Finches from humid habitats independently learned how to drop a twig into the crevice of an artificial log to pull out beetle larvae, even though their own parents did not use tools. In contrast, adults from the humid habitat continued to forage with their bills, the old-fashioned way, even when given the opportunity to watch other Woodpecker Finches using twigs. The study demonstrates the importance of environmental factors and early learning in a species with an apparent predisposition for using tools.

Source: Tebbich, S., M. Taborsky, B. Fessl, and D. Blomqvist. 2001. Do woodpecker finches acquire tool-use by social learning? Proceedings of the Royal Society of London Series B 268:2189-2193.

Clark's Nutcrackers can store up to 33,000 pine seeds in more than 2,500 cache sites during a good autumn. Researchers have shown that nutcrackers can remember the locations of thousands of caches, relocating them using landmarks. New experiments show that Clark's Nutcrackers remember the size of their seeds, too. They opened their bills wider to probe sand where they had buried large seeds than where they had buried small seeds. Researchers hypothesize that this ability allows nutcrackers to recover seeds more efficiently.

Source: Møller, A., B. Pavlick, A. G. Hile, and R. P. Balda. 2001. Clark's Nutcrackers Nucifraga columbiana remember the size of their cached seeds. Ethology 107:451-461.

Donald Waite/CLO

A Rufous Hummingbird remembers flower color, location, and nectar quality as it forages. After draining a flower of nectar, it uses these cues to avoid visiting the empty flower on subsequent visits. A recent study shows that Rufous Hummingbirds can distinguish among at least three different categories of flowers: those emptied on a previous visit, those seen on a previous visit, and those that have newly appeared. The study shows that the hummers also remember flower height, a useful cue when foraging in three dimensions.

Source: Henderson, J., T. A. Hurly, and S. D. Healy. 2001. Rufous hummingbirds' memory for flower location. Animal Behaviour 61:981-986.