Cracking Food
Reports
There is no doubt that birds are clever animals. For example, there is a worldwide phenomenon involving over thirty species of crows, gulls and raptors taking advantage of rocks, pavements and solid surfaces to crack into nuts, bones, molluscs and other hard-shelled food by dropping them from a height. On Arran this is most clearly demonstrated by some of our gulls and crows dropping cockles, winkles and other molluscs onto rocky shores, piers and parking areas adjacent to the shore. Carrion Crows, Hooded Crows and Herring Gulls seem to be particularly adept at it and have been well captured in Arthur Duncan’s photographs.
Over the last hundred years there have been numerous scientific studies of this phenomenon. It involves more sophistication than just carrying the potential food into the air and dropping it. The food is deliberately dropped onto hard surfaces rarely water. Shells are selected according to size and the dropping height is fine tuned to effectively crack shells according to size and weight. Not surprisingly immature birds are less efficient than adults in cracking shells. The skill could be innate, but these studies suggest that the behaviour is consistent with learning.
Next time you notice crows and gulls dropping objects over rocky shores or notice broken shells strewn across hard areas adjacent to the shore, never mind the mess, just think about the incredible capacity for avian learning and ingenuity.
