Eurasian tree sparrows are more food neophobic and habituate to novel objects more slowly than house sparrows

We captured wild Eurasian tree sparrows (Passer montanus) from a private field site in Illinois, United States. Sparrows were transported to Louisiana State University where we conducted neophobia trials. These behavioural assays consisted of weeklong trials to assess responses to novel objects and foods as well as the sparrows' abilities to habituate to repeated presentations of the same initially novel object. We followed methods used in Kimball et al. 2022 (Novel objects alter immediate early gene expression globally for ZENK and regionally for c-fos in neophobic and non-neophobic house sparrows, published in Behavioural Brain Research). Behavioural trials were recorded, and then the recordings were watched by two observers (KJK and EBC). Video watchers noted the time during the hour-long trials at which each sparrow approached and fed from the food dish, where novel objects or foods were placed. Because male and female Eurasian tree sparrows cannot be distinguished by plumage characteristics, we determined the sex of each sparrow by examining gonads in the body cavity after the birds were euthanized after behavioural trials. We compared the Eurasian tree sparrows' behavioural responses to those of house sparrows (Passer domesticus) collected in a previous study (Kimball et al. 2022). Again, house sparrow data were collected using the same methods. The manuscript and its associated dataset for the house sparrow study can be accessed here: https://doi.org/10.1016/j.bbr.2022.113863. For more details on our methods, please read the associated manuscript.