to eat, or to sing, or to vomit into the mouths of their children
It prompts the parent bird to feed them.
They open their mouths on land, and led birds eat the food on their teeth. Hope this helps.
Innate.
Crocodile and Hippos because when they open their mouths the birds will peck all off the bacteria and leftovers.
They normally lie with their mouths partly open, and the local birds pick off any bits of flesh from the teeth.
Crocodiles clean their teeth by opening their mouths wide and allowing small birds called "crocodile birds" to pick food bits and debris from between their teeth. This cleaning symbiosis benefits both species as the birds get a meal and the crocodiles get their teeth cleaned.
Crocodiles are often seen on the beach, looking like they are asleep, with their mouths open. What they are doing is basking, they keep their mouths open to regulate their body temperature. People sweat, dogs and cats pant, and crocodiles open their mouths :)
eels must open and cloth their mouths constantly in order to circulate water over their gills
Birds use their tongues to taste, they use their beaks/ mouths to drink.
they open their mouths and eat.
for food
No.