A pair of common loons with eyes locked on each other in a behavior known as the circle dance on Pawtuckaway Lake in Nottingham. This behavior involves two rival loons swimming circles around each other as a test of fitness. Cabinet photo by CHRISTOPHER ROBERSON

A common loon displaying a behavior known as the penguin dance on Pawtuckaway Lake in Nottingham. This behavior is a response to stress or a threat. Cabinet photo by CHRISTOPHER ROBERSON