Aims: The main aim of this study was to investigate the small scale spatio-temporal variations (during a fruiting season in different microhabitats) in Spindle Euonymus europaeus fruit consumption by birds. Specifically, variations were tested taking into consideration the configuration of the visiting assemblages, visit frequency, amount of fruit consumed per visit, and methods of taking the fruits.
Location: A 1 km2 plot situated in the Torío river valley (900-1000 m a.s.l.), León province, NW Spain.
Methods: Four plants with a maximum distance of 0.5 km between them situated in different microhabitats were used to study fruit consumption. The sampling unit was the feeding visit. The number of fruits eaten by each bird during each feeding visit and the method of taking the fruit were also recorded. The persistence of ripe fruit in all the plant species with fleshy fruits was checked weekly, and data was obtained on the seasonal availability of insects and other invertebrates. Bibliography was consulted for quantitative data on fleshy fruit availability and bird density in the area during the study period. The statistical analyses included the chi-square association test (?2), Poisson rates test (z), t-test, Mann-Whitney U-test, and Kruskal-Wallis test (K).
Results: Considering the overall data (330 feeding visits), the species that most frequented the Spindles were the Blackcap Sylvia atricapilla (40.6%), Robin Erithacus rubecula (33.9%), and Song Thrush Turdus philomelos (13.6%). Significant differences in the visiting assemblages were recorded among the shrubs. The larger bird species consumed significantly more fruits per feeding visit than the smaller ones (Song Thrush: 11.9 fruits/visit, n = 45 visits; Blackcap: 4.2, n = 134; Robin: 3.0, n = 112). The amount of fruits eaten by some species per visit and the removal method used varied significantly among plants and temporally.
Conclusions: Spatio-temporal changes were probably related to the characteristics of each microhabitat, plant physionomy, bird movements, and temporal changes in food accessibility and energy demand. The variations observed in the frugivorous avian assemblages within both bird species and species groups (disperser and non-disperser), though the latter differences were subtle and non-significant, could affect Spindle local demography.
