Note lack of a rear toe, thus the name "tridactyla." These kittiwakes are in breeding plumage, lacking the dark hind-neck they acquire in the winter. Pacific birds such as these are larger and have a longer bill than the nominate race of the North Atlantic. Interestingly Atlantic birds are more successful at reproduction, but Pacific kittiwakes live longer. Canon PowerShot SX50 HS
Reference:
Hatch, Scott A., Gregory J. Robertson and Pat Herron Baird. (2009). Black-legged Kittiwake (Rissa tridactyla), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/bklkit