The key role of a Ring Ouzel Turdus torquatus wintering population in seed dispersal of the endangered endemic Juniperus cedrus in an insular environment

Abstract

Although the Ring Ouzel has been considered accidental in the Canary Islands, it has been observed for the last five years in the high mountain zone of Tenerife (Canary Islands), showing it to be a regular winter visitor. Its inter- action with female Juniperus cedrus cones and seeds was studied by analysing its wintering diet during January–April 2008. This juniper is endemic to the Canaries and Madeira and is classified as endangered by the IUCN. Previously, its sole long-distance disperser was known to be the Raven Corvus corax, which is unfortunately now extinct in the distribution range of J. cedrus. The results show that the diet of T. torquatus in Tenerife consists mostly of female J. cedrus cones (95% of the biomass consumed). Due to the large amount of seeds dispersed by Ring Ouzels and the effectiveness in seed germination, this winter visitor constitutes an important vector in the dispersal of J. cedrus that appears to have gone undetected in the past. This passerine plays a key role in its seed dispersal system, being able to move seeds over long distances, thus connecting fragmented populations of this plant. The present work is one of the few cases described in which a plant endemic to an oceanic island is so dependent on a winter visitor, and highlights the importance of insular environments in the wintering range of the Ring Ouzel. Owing to the absence of native long-distance seed dispersers, the future fate of this conifer is now probably dependent on the wintering population of this thrush.