Effects of crop size and stand size on seed removal by vertebrates in hazel Corylus avellana

Crop size was examined in 180 bushes of hazel in 13 different stands growing in open habitats (3) and forest (10). Seed removal rates were calculated for all bushes with nuts (154). Individual crop sizes, total crop size of the stands and local seed density (number of nuts within 5 m from sampled bushes) were estimated. Average crop sizes and removal rates differed significantly between stands. The prediction that seed removal is slower in large stands than in small ones was supported. All viable nuts were removed before winter. Nutcrackers seem to prefer large stands in open habitat while squirrels were observed only in stands growing in forest. Seed removal rates from individual bushes were positively related to the combined crop of neighbouring (within 5 m) bushes. In stands growing in forest removal rate was also positively correlated with individual crop size. The total crop of all bushes in a stand determined the general level of seed removal, while the crops of an individual bush and that of its close neighbours appeared to influence the removal rates from each individual bush.