The estimated OR gene repertoire sizes of 13 species of birds representing eight orders.

<p>Open and grey bars represent the estimated total number of functional and non-functional OR genes, respectively. Data are from this study (OHB = Oriental honey buzzard), Warren et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130191#pone.0130191.ref041" target="_blank">41</a>] (zebra finch), Zhan et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130191#pone.0130191.ref042" target="_blank">42</a>] (falcon 1 = peregrine falcon, falcon 2 = saker falcon), Doyle et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130191#pone.0130191.ref043" target="_blank">43</a>] (golden eagle) and Steiger et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130191#pone.0130191.ref038" target="_blank">38</a>] (all other species). Note that Doyle et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130191#pone.0130191.ref043" target="_blank">43</a>] did not distinguish between the number of functional and non-functional OR gene.