 Several terrestrial starlings , including those in the genus Sturnus , have adaptations of the skull and muscles that help with feeding by probing . This adaptation is most strongly developed in the common starling ( along with the spotless and white @-@ <unk> starlings ) , where the <unk> muscles responsible for opening the jaw are enlarged and the skull is narrow , allowing the eye to be moved forward to peer down the length of the bill . This technique involves inserting the bill into the ground and opening it as a way of searching for hidden food items . Common starlings have the physical traits that enable them to use this feeding technique , which has undoubtedly helped the species spread far and wide . 
