Acorn Preference of Urban Blue Jays (Cyanocitta cristata) during Fall and Spring in Northwestern Arkansas
1991; Oxford University Press; Volume: 93; Issue: 2 Linguagem: Inglês
10.2307/1368961
ISSN1938-5129
AutoresTodd L. Scarlett, Kimberly G. Smith,
Tópico(s)Ecology and Vegetation Dynamics Studies
ResumoWe censused 26 acorn-bearing trees of six oak species for Blue Jays (Cyanocitta cristata) during fall of 1985 on the University of Arkansas campus. The following spring we presented six piles, each containing 20 acorns from a different oak species, to free-ranging jays to determine acorn preference in spring. Trees censused and acorns presented were from both black oak (BO) and white oak (WO) subgenera, which differ in size, percent fat, tannin content, and germination time. In fall, Blue Jays were observed removing acorns from three species of oaks with small acorns, particularly those of willow oaks (BO, Quercus phellos), and were rarely observed in trees of three other oaks with large acorns. When offered a choice of acorns from six oak species in spring, Blue Jays showed a preference, based on Ivlev's electivity index, for small acorns, particularly those of pin oaks (BO, Q. palustris), and an avoidance of large acorns. Thus, small size appears to be an important trait associated with acorn preference in Blue Jays. Acorns of the introduced English oak (WO, Q. robur), which are preferred by Euorpean Jays (Garrulus glandarius) (Bossema 1979), also were avoided in spring by Blue Jays, suggesting that familiarity may be a general component of acorn selection by jays.
Referência(s)