Eurasian Jay (Garrulus glandarius) acorn choice experiment: data and analysis script

Aim of the Study:
This study aimed to determine if the acorn preference of food-hoarding Eurasian jays (Garrulus glandarius) is fixed or context-dependent. We tested whether the jays' choice of acorn quality (intact, holed, or damaged) changes based on the relative availability of each type.
Methodology:
The data were collected from a field experiment at five forest sites in Ås, Norway. Wild jays were presented with a choice apparatus consisting of three trays, each holding five acorns of a specific quality: (1) Intact, (2) Holed (drilled to mimic weevil damage), and (3) Damaged (natural rodent damage).
A time-lapse camera recorded 318 individual acorn selections. The primary data file (Data_for_Analysis.csv) contains each choice event, recording which acorn type was chosen and the precise number of acorns of all three types that were available at that specific moment. The accompanying R script (acorn_choice_brms.R) was used to fit a Bayesian multilevel categorical regression model to analyze these choice data.
Ethical Note:
The study involved non-invasive field observations of wild birds only; no capture or marking occurred. Access to the study sites was granted by landowners. No permits were required under Norwegian regulations.