Back of the head of a <a href="https://en.wikipedia.org/wiki/Mute_swan" class="extiw" title="en:Mute swan">mute swan</a> (<i>Cygnus olor</i>).
<a href="//commons.wikimedia.org/wiki/User:Yerpo" title="User:Yerpo">Yerpo</a>
<span class="int-own-work" lang="en">Own work</span>