Note 8 — Chapter I · —INTRODUCTION.
Reading edition
E. Selous, "Sexual Selection in Birds," Zoölogist, Feb., 1907, p. 65; ib., May, p. 169. Sexual aberrations generally are not uncommon among birds; see, e.g., A. Heim, "Sexuelle Verirrungen bei Vögeln in den Tropen," Sexual-Probleme, April, 1913.