The authors write "So far, the rich-club has been conceptualized as a large-scale brain network phenomenon in adult humans (van den Heuvel and Sporns, 2011), human newborns (Ball et al., 2014), macaque monkey (Harriger et al., 2012), the nematode worm Caenorhabditis elegans (Towlson et al., 2013), and mouse hippocampus (Schroeter et al., 2015)."
This list should have included the pigeon (Shanahan, et al., 2014):
Shanahan, M., Bingman, V., Shimizu, T., Wild, M. & Gunturkun, O., Large-Scale Network Organisation in the Avian Forebrain: A Connectivity Matrix and Theoretical Analysis, Frontiers in Computational Neuroscience, vol. 7 (2013), article 89.
http://journal.frontiersin.org/article/10.3389/fncom.2013.00089/full
In particular, see Figure 8 and the relevant text.
None declared