They don't store food in the pouch on their bills. The large, fibrous skin pouch that dangles from a pelican's bill is called the gular pouch (or, occasionally, the gular sac). Many people mistakenly believe it’s used to store food, like a built-in lunch box. The idea was popularized by a limerick of unknown authorship:
“A wonderful bird is the pelican. His beak can hold more than his belly can. He can hold in his beak enough food for a week. But I’ll be damned if I can see how the helican."
While the rhyme is amusing, it isn’t accurate. In reality, pelicans use their gular pouches as a means of capturing food—not as a place to keep it tucked away for extended periods. The highly-flexible sacs can expand or contract, and the lower jaw bones they’re connected to are capable of bowing outwards, which enables the birds to use their sacs as fishing nets. Once a pelican captures its prey, the bird drains any water it may have accidentally captured with it by tilting its head and contracting those pouch muscles. (Fun fact: Some species can hold 11 litres worth of liquid in their gular sacs.) Usually, the prey is swallowed immediately after the water purge.
S 34° 08.620′ E 139° 08.108′