Dependence of Clark's nutcracker, Nucifraga columbiana, on conifer seeds during the postfledging period.

Abstract

Observed nutcrackers recover stored whitebark pine Pinus albicaulis seeds in subalpine areas at Grand Teton and Yellowstone National Parks, Wyoming, during June and July of 1979-81. Seeds from caches were the only food items seen fed to young. Of 163 caches located by adult nutcrackers, 20% contained germinating seeds. Juvenile nutcrackers learned to find caches by locating germinating seeds, and so became independent of their parents about mid-July. Behavior of nutcrackers of foraging on pinon P. monophylla and limber P. flexilis pine cones was also studied in the Raft River Mountains, Utah, from August-October 1978 and 1980. Juveniles began foraging on cones in mid-August and first cached seeds in early to mid-September, both forms of behavior occurring 2-3 wk later than in adults. Juveniles foraged significantly more slowly than adults in late August and early September, but after 15 September their foraging rates were similar. Juveniles were highly aggressive towards foraging adults prior to 7 September, but not thereafter.-from Authors