Caspian Gull
...that the Caspian Gull is regarded by some authorities as a subspecies of the Herring Gull or Yellow-legged Gull, and by others as a separate species?
...that the <b id="mwAsM"><a class="mw-redirect" href="./Caspian_Gull" id="mwAsQ" rel="mw:WikiLink" title="Caspian Gull">Caspian Gull</a></b> (<i id="mwAsU">pictured</i>) is regarded by some authorities as a <a href="./Subspecies" id="mwAsY" rel="mw:WikiLink" title="Subspecies">subspecies</a> of the <a class="mw-redirect" href="./Herring_Gull" id="mwAsc" rel="mw:WikiLink" title="Herring Gull">Herring Gull</a> or <a class="mw-redirect" href="./Yellow-legged_Gull" id="mwAsg" rel="mw:WikiLink" title="Yellow-legged Gull">Yellow-legged Gull</a>, and by others as a separate <a href="./Species" id="mwAsk" rel="mw:WikiLink" title="Species">species</a>?