A simple cage test captures intrinsic differences in aspects of personality across individuals in a passerine bird

Personality tests are best carried out in an artificial, standardized
environment. There is a need to develop reliable approaches
for testing wild individuals in a manner that minimizes harm or
stress to individuals while allowing maximal flexibility (e.g.
a portable set-up or short protocols) for researchers.We developed
a behavioural assay of personality traits for a wild-caught bird
placed in a standard bird cage, which takes approximately 15 min
per assay. After 10 min acclimation, we quantified neophobiarelated
behaviour (in terms of time spent in different parts of the
cage), activity (movement through the cage by hops or short
flights) and the time it took to escape from the cage after opening
the cage door in 293 assays of 224 individual blue tits, Cyanistes
caeruleus, carried out during three consecutive winters. Neophobiarelated
behaviour and escape time were significantly repeatable
and showed no annual or within-year temporal variation or
differences between sexes or age classes. Escape time was associated
with one of two single nucleotide polymorphisms in exon 3 of
the DRD4 gene that we considered as candidates. This gene is the
prime candidate for novelty-seeking behaviours and this genomic
region has been found to associate with exploration score in the
closely related great tit, Parus major.We conclude that our assay can
capture repeatable and heritable differences in aspects of personality
among wild individuals.