Black-legged kittiwake (Rissa tridactyla) in Courtship, UK Black-legged kittiwake (Rissa tridactyla) in Courtship. They like most birds have a courtship ritual. Although not always elaborate especially if you are not paying attention. These two are going through the motions at the intended nest site. Of real interst to me in this image is the differnce in beak/bill colour. Mature birds should have a yellowish bill.