Animals & nature · 2021
Did more oak seedlings emerge where magpies hid more acorns?
Yes. In this field study, places with a higher density of holm oak acorns hidden by Eurasian magpies also had a higher density of newly emerged oak seedlings the following spring. This was an observed relationship, not proof that the birds’ choices alone caused the pattern.
Details
Researchers used radio-tracking and automatic wildlife cameras to follow where magpies hid acorns in a landscape combining farming and trees. They then examined how the density of hidden acorns related to the density of emerging seedlings across habitats.
Breeding magpies hid acorns within their caching territories. They preferred tilled ground over oak plantations and mostly avoided old fields. These habitat preferences were strongest at short to medium distances from the acorn source, where most acorns were hidden; at long distances, the differences weakened or disappeared. The birds also selected particular hiding spots within habitats.
The following spring, denser acorn stores were associated with denser seedling emergence. The researchers interpreted the birds’ territories and site preferences as helping shape where young oaks appeared. The reported relationship concerns seedling emergence, however, not whether those seedlings survived to become established trees.
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