Table 1.

Possible similarities of sex differences in brain, physiology and behavior in mammals and birds.

Similarities		Typical literatures
1	Sex differentiation of core sexual behavior is mainly induced by the exposure of gonadal hormones during development	Arnold and Chen, 2009; Maekawa et al., 2013 (also, 2–5)
2	The structure of BNST (M > F) is sexually differentiated mainly by the exposure of gonadal hormones during development	Tsukahara et al., 2011
3	Sex chromosomes in brain affects sexual dimorphism observed in communication such as song production in bird and social behavior in mouse	Agate et al., 2003; Cox and Rissman, 2011
4	Sex-biased local synthesis of neuroestrogen (M > F)	Hojo et al., 2009, 2014
5	Sexual differentiation of neuronal structures related to circadian timing could be affected by sex chromosomes in the brain	Kuljis et al., 2013