This means that the largest Procellariiform is 8.6 times as long, 11.25 times as large in the wingspan and 274 times as heavy as the smallest. This is a good example of the fact that while area increases approximately to the squared power of length, mass or volume increases with the to the cubed power of length. All members of the Procellariiformes feed at sea. What they feed on varies depending on species but generally, if it can be found near or on the surface of the sea and it can be swallowed, it will be eaten. A number of the smaller species feed on crustaceans while larger ones tend to take squid and fish.
Many species are scavengers eating whatever can be found on the surface.
Many species are also found in association with Whales, Dolphins and schools of larger fish. In these circumstances they are either feeding on the same items as the animals involved or on the scraps and refuse left from the 'mammals' or 'fishes' feeding. Associations between Petrels and fish are sufficiently well known for Irish Fishermen to call the Manx Shearwater 'Mackerel Cock' recognising it as an indicator of fish shoals. Associations with marine mammals are also well known and Blue Petrels and Prions are known as 'Whale Birds'. Past whalers knew it was no use looking for whales if there were no birds present.