- Vaughan, Eleta J.
The Graduate School, University of Maine
Acorn dispersal by blue Jays from a stand of 111 northern red oak trees was studied near Blue Hill, Maine in 1988, a poor acorn crop year, and in 1989, a relatively good acorn production year. Ten times more acorns were produced in 1989 (128,339) than in 1988 (11,792). The proportion of acorns that were viable differed significantly (1.2% in 1988 and 55.2 % in 1989). Acorn dispersal was synchronized with acorn production in the stand, which was one month earlier in the poor year (dispersal ended on Oct. 7, 1988 and Nov. 6, 1989).
The overwintering blue jay population was estimated to be 51 to 71 jays. Blue jay dispersal activity was not constant over the dispersal period nor throughout the day. The greatest rate of dispersal activity was near the end of the dispersal period (four days before the end of dispersal in 1988 and one day before 1989). The greatest hourly dispersal activity occurred approximately three hours after sunrise. Blue jays flew fewer dispersal trips than has been observed in other blue jay dispersal studies (an estimated 23 to 37 trips per jay) and the mean number of acorns dispersed per tree was low (10.8 in 19088 and 15.2 in 1989). Blue jays did not disperse acorns from three trees with larger acorns than those in the stand and may select trees with smaller acorns.
Fourteen percent of acorns dispersed by blue jays ere cached in or beside fields in environments that are not favor able for oak establishment. Although 82% of dispersed acorns were taken into forest where low light conditions may cause high seedling mortality, blue jays may still favor of oak regeneration by increasing acorn survival overwinter and by placing some seedlings in edge habitat or canopy gaps. Blues jays in Maine clearly have the pontential to facilitate oak establishment.