Massive and effective acorn dispersal into agroforestry systems by an overlooked vector, the Eurasian magpie (Pica pica) Martínez Baroja, Loreto Leverkus, Alexandro B. Castro Gutiérrez, Jorge Molina Morales, Mercedes Abandoned fields Corvidae Oak forest regeneration Quercus ilex Scatter-hoarding Zoochory Oak regeneration and the expansion of forested sites in Eurasia rely on acorn dispersal by animals, especially the Eurasian jay (Garrulus glandarius). However, in open agroforestry systems where jays are absent, such as old fields far from acorn sources, oak recruitment still occurs. We hypothesize that the Eurasian magpie (Pica pica), an abundant corvid in this system, substitutes the jay in its seed dispersal function. By ringing 169 magpies, video recording >7500 acorn removal events with trail cameras, and radiotagging 337 acorns, we quantified that (1) magpies cached 41–56% of the annual acorn production of Quercus ilex trees in single caches on the ground; (2) breeding pairs, and especially males, were the main acorn dispersers; (3) each breeding magpie cached 169–1372 acorns in 6 weeks; and (4) the effectiveness of dispersal (percentage of cached acorns resulting in seedlings) was 0.6–2.4%, which (5) yielded a high density of emerged seedlings (56–439 seedlings/ha). We evidence that magpie could be a key species in the regeneration of oak agroforestry mosaics because they massively and effectively dispersed acorns. However, in our particular study site, effectiveness was low probably due to herbivory and summer drought stress (i.e., a context limitation rather than an intrinsic limitation of the disperser). As the distributions of magpies and oaks overlap widely in Eurasia, effective acorn dispersal by magpies could have a significant role in largescale oak forest recovery in strongly fragmented landscapes. 2020-02-14T08:16:26Z 2020-02-14T08:16:26Z 2019 info:eu-repo/semantics/article Mart ınez-Baroja, L., L. P erez-Camacho, P. Villar-Salvador, S. Rebollo, P. Quiles, D. G omez-S anchez, M. Molina- Morales, A. B. Leverkus, J. Castro, and J. M. Rey-Benayas. 2019. Massive and effective acorn dispersal into agroforestry systems by an overlooked vector, the Eurasian magpie (Pica pica). Ecosphere 10(12):e02989. http://hdl.handle.net/10481/59658 10.1002/ecs2.2989 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España Ecology Society of America