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brain size. (Their brain-to-body ratio equals that of dolphins and nearly matches our own.) Whatâs more, their large brains are packed tight with exceptionally large numbers of brain cellsâ (p. 29). Skutch (1996) writes: âOrnithologists are sometimes asked which birds are most intelligent. An answer often given is crows, ravens and related birdsâthe corvids. These large, aggressive, opportunistic omnivores exhibit great behavioral flexibility by taking foods so diverse as fruits, insects, small living vertebrates, carrion, and much else. When removed from the nest before they are well feathered to be hand-raised, they become strongly attached to their foster parents, often regarding one as a mate. Their tameness recommends them for the intelligence tests that experimenters give them in laboratories, and they make relatively good scores. Their intelligence won them a place at the summit of the evolutionary tree in certain older systems of classification, although now, as in the most recent check-list of the American Ornithologistâs Union, they are placed near the bottom of the Oscine passerines, with finches, weavers, and allied families at the top. The great difficulty of sharply separating learned or innovative behavior, on the one hand, and innate or genetically determined behavior, on the other, and the vast diversity of the lifestyles and activities of birds, make it impossible to decide which are most intelligentâ (pp. 120â21).

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P. 15: CLARKâS NUTCRACKERSâ MEMORY OF CACHES

Kamil and Balda (1985) write: âNutcrackers expend substantial amounts of time and energy during the late summer and fall harvesting seeds from pine cones, transporting them up to 22 km, and then burying the pine seeds in thousands of discrete caches. In a year of a heavy pine seed crop, a Clarkâs nutcracker may store between 22,000 and 33,000 seeds, and a single Eurasian nutcracker between 86,000 and 100,000 seeds. These seeds are then recovered over the course of the next 11 months and form the bulk of the diet during the winter and during the breeding season. The nutrients and energy obtained from cached seeds allow the nutcracker to overwinter and breed early in the year in harsh alpine habitats where other foods are often rare to nonexistent. Field observations suggest that nutcrackers accurately find specific locations of hidden caches up to 11 months after making themâ (pp. 95â96).

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P. 15: SCRUB JAYS WITH FORESIGHT

Emery and Clayton (2001) write: âTo our knowledge, this is the first experimental demonstration that a non-human animal can remember the social context of specific events, and adjust their present behavior to avoid potentially detrimental consequences in the future, in this case pilfering. To do this, scrub jays need experience of pilfering another birdâs caches, but do not require experience of observing a conspecific hide food. They can recall specific past events, but the present results raise the possibility that they can also plan for the future. The jays seem to have transferred their previous experiences of being a pilferer to the current situation in which their own caches might be stolen. This may be a good candidate for knowledge attribution to conspecifics (seeing leads to knowing), use of this knowledge to influence subsequent behavior (re-caching in new locations) or even tactical deception. Mental time travel (episodic memory and future planning) and mental attribution were thought to be unique to humans. The cache recovery model presents a new way of addressing these issues in animalsâ (p. 445).

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P. 15: PIGEONS CAN TELL VAN GOGH FROM CHAGALL

Watanabe (2001) writes: âIn Experiment 1, pigeons were trained to discriminate between paintings by Van Gogh and Chagall. After training, the subjects were tested with different paintings by the same artists. The subjects showed generalization to these paintings. The subjects maintained their discriminative ability for black-and-white paintings and partially occluded paintings. When they were tested with mosaic paintings, the number of correct responses decreased, depending