HOW DO NUTCRACKERS FIND THEIR CACHES? Over the years many naturalists have been intrigued by the unhesitating way in which birds of both nutcracker species fly to the ground and unearth pine nuts with a few swipes of the bill, as if knowing exactly where to dig. Even snow is no deterrent. Claude Crocq has described how European Nutcrackers in the French Alps recover pine nuts by tunneling to caches concealed by more than a meter of snow. Their tunnels frequently curve beneath the snow, and while excavating, the completely submerged bird cannot see out (Figure 6.1). Yet more than three-fourths of 125 such galeries bore the tell-tale evidence of seed-coat fragments, attesting to the excavator's success.
Vander Wall and Hutchins watched a Clark's Nutcracker peck through a half-inch crust of ice at the edge of a melting snowpack to recover whitebark pine seeds buried beneath the ice. The bird spent seventy-five seconds on this task, no trivial expenditure of its time. What makes such feats remarkable is that winter snows so completely modify the cache environment that a bird must find many caches in order to survive, and that some caches may be retrieved ten months after having been made.
Do nutcrackers smell the buried seeds? Pine seeds are often sticky with drops of resin that have gotten on them while in the cone. Conceivably, the resinous odor could be detected by a nutcracker even through the soil, especiauy if the cache is a large one. True, most corvids do not have a highly developed sense of smell, but Black-billed Magpies have been known to detect a decaying chicken hidden beneath an underwater rock, and have been at-