Acorn caching hotspots of the Eurasian jay in pine plantations: Ecological basis for understorey management to assist oak regeneration

Monospecific pine plantations are highly vulnerable to disturbance. Promoting oak regeneration through assisted restoration by effective acorn dispersers, such as the Eurasian jay ( Garrulus glandarius L.), could significantly enhance their ecological resilience. However, our ability to design targeted management interventions that harness jay‐assisted oak regeneration is constrained by limited knowledge of how this corvid selects understorey microsites for caching acorns in these plantations.

To inform jay‐assisted oak regeneration in pine plantations, we examined how understorey structure influences jay acorn caching behaviour in two ecologically contrasting oaks, Quercus ilex L. and Quercus faginea Lam. We selected three sites within a 55‐year‐old monospecific Pinus pinaster Lam. plantation that differed in density due to thinning. For two consecutive dispersal seasons, we quantified dispersal distances and the microsite caching preferences of jays using acorn radio‐tracking.

Jays cached all acorns within the pine plantation and avoided wide natural or artificial gaps. Proportion of cached acorns was similar for both oaks, with no significant differences in dispersal distance kernels. Jays strongly selected large shrubs, mainly Cistus spp., with a tendency to select shrub‐abundant patches and cache acorns closer to pine trunks than expected by chance; these patterns were unrelated to oak species.

Jays did not use coarse wood for caching, and caches were no less frequent in furrows or mounds from site preparation to establish the plantation than in undisturbed ground. Between 1.2% and 10.7% of cached acorns produced seedlings that survived their first summer.

Synthesis and applications . Our findings show that Eurasian jay dispersal activity depends on specific understorey structures when selecting caching microsites—particularly shrub cover and standing pines. These features could be directly shaped by management to promote assisted natural oak regeneration. By fostering structurally diverse understories, managers can enhance seed dispersal services and accelerate the transition of vulnerable pine monocultures towards more resilient mixed forests.