Seed dispersal of Japanese stone pine by the Eurasian Nutcracker
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Seed dispersal of Japanese stone pine <i>Pinus pumila</i> by the Eurasian Nutcracker <i>Nucifraga caryocatactes</i> was studied at Mt. Apoi in Hokkaido, northern Japan. The seed foraging and caching behavior of diurnal birds and mammals was observed, and the relative importance of each species for pine seed dispersal was examined. All mature cones disappeared from the pine shrubs by mid-October each year regardless of the cone crop size. Eurasian Nutcrackers, Varied Tit <i>Parus varius</i>, Eurasian Nuthatch <i>Sitta europaea</i>, Red Squirrel <i>Sciurus vulgaris</i>, and Siberian Chipmunk <i>Tamias sibiricus</i> were all potential seed dispersal agents, however, observations revealed that nutcrackers carried 96% of all seeds transported from the pine trees. The nutcracker carried 142 seeds on average (max. 209) in one trip. Nutcrackers mainly carried pine seeds into their mixed coniferous forest, breeding habitat, where stone pines cannot normally become established and cached them in the soil there. Nutcracker caches averaged 12 seeds with a maximum of 51 seeds. Pine seedlings were found growing in clusters (in groups of two or more trees). The number of seedlings per cluster closely resembled the number of seeds in nutcracker caches. Results suggest that most stone pine seedlings originated from nutcracker caches. Eurasian Nutcrackers thus play an important role in the regeneration of Japanese stone pine despite their small number of caches.
- ORNITHOLOGICAL SCIENCE
ORNITHOLOGICAL SCIENCE 2(1), 33-40, 2003
The Ornithological Society of Japan