Tichodroma (Dec 2016)
Ďatle ako konzumenti imág lykožrúta smrekového (Ips typographus) počas zrelostného žeru: prípadová štúdia / Woodpeckers as consumers of adult spruce bark beetles (Ips typographus) during maturation feeding: a case study
Abstract
At least 10 woodpeckers of 4 species excavated bark beetle imagoes during their maturation feeding within a 0.25 ha forest spot with 6 Norway spruces trees (Picea abies) infested by the European spruce bark beetle (Ips typographus) near Zvolen (central Slovakia) during one day of continuous observations (12 September 2015, from 6:00 a.m. to 7.00 p.m. of CEST): 2 males, 3 females and 1 young of Dendrocopos major, 1 female of D. medius, 1 female of D. leucotos, and 1 male and 1 female of Dryocopus martius. Up to 4–6 woodpeckers excavate simultaneously within the infested spot. Woodpeckers excavating I. typographus spent on one tree continuously 4–84 min (28 min in average). From the total time spent by individual woodpeckers by excavation (951 “woodpeckerminutes”), 17% of excavating activity was associated with D. major males, 55% with D. major females, 8% with D. major young, 2% with D. medius female, 9% with D. leucotos female, 7% with D. martius male and 2% with D. martius female woodpeckers. At least one excavating woodpecker was observed within the infested spot in 57% of the total time of observations. Excavation of bark beetles by woodpeckers peaked between 5:00 and 6:00 p.m. Woodpeckers excavated bark beetles on a trunk singly in 34 cases. In 27 cases, 2–3 woodpeckers excavated simultaneously on the same trunk, but only in 9 cases an aggressive encounter was observed resulting in driving away of one woodpecker from a trunk. D. major consumed approximately 9 bark beetle imagoes per one minute of excavation, averagely 1122 imagoes per day. A mean predation rate for bark beetle imagoes was estimated to be 47% (95% confidence interval 32–67%). The number of bark beetles predated by D. major would be able to attack potentially on average further 15–67 spruces in the next year depending on their physiological state.
