Red knots migrate between their breeding grounds in the Arctic and their wintering grounds in West Africa. Chicks currently born under rapidly warming conditions attain smaller sizes before migration starts,because they miss the insect peak. whether they reach their wintering grounds in the tropics, they are faced with a second disadvantage: their shorter bills cannot reach their favourite shellfish food. This results in an evolutionary force towards smaller-sized birds with large bills.
Source: phys.org