Bali Duck
...that the gene that creates the crest of the Bali Duck also causes physical defects which can kill it before it hatches?
...that the <a href="./Gene" id="mwYw" rel="mw:WikiLink" title="Gene">gene</a> that creates the crest of the <b id="mwZA"><a class="mw-redirect" href="./Bali_Duck" id="mwZQ" rel="mw:WikiLink" title="Bali Duck">Bali Duck</a></b> also causes <a href="./Genetic_disorder" id="mwZg" rel="mw:WikiLink" title="Genetic disorder">physical defects</a> which can kill it before it <a class="mw-redirect" href="./Egg_(biology)" id="mwZw" rel="mw:WikiLink" title="Egg (biology)">hatches</a>?