AVIAN FRUGIVORY ON A GAP-SPECIALIST, THE RED ELDERBERRY (SAMBUCUS RACEMOSA)

Abstract

In the temperate zone, few plants produce fruit during the peak of the avian breeding season when arthropods are abundant. This study examined avian frugivory on red elderberry (Sambucus racemosa pubens), a gap-specialist that fruits in late June and early July. First, we videotaped fruiting elderberry plants (n = 67 hr) within a forest to determine which avian species ate elderberry fruit. The birds that fed most frequently on red elderberry fruits were Scarlet Tanagers (Piranga olivacea) and Rose-breasted Grosbeaks (Pheucticus ludovicianus). We then analyzed radiotelemetry data for Scarlet Tanagers to determine (1) whether tanagers shifted their territories when elderberry was in fruit, and (2) whether tanagers traveled long distances off territory to visit fruiting elderberry. During the fruiting period, male tanagers shifted their home ranges and spent more time near elderberry bushes; however, they left their territories only 0.25 times per hr and moved an average of only 115 m during trips off territory. These results suggest that while tanagers do focus their activity near fruiting elderberry, they do not leave their territories regularly to find fruit.