About this photo:

These were very common on the Galapagos. This species was recently split from the very similar Masked Booby (Sula dactylatra). The two species are said to be separable based on the color of the bill, which is orange in this species and yellow in the Masked Booby. An easier way is based on range, as the two species barely overlap, the Nazca Booby appearing in the Pacific, with the Masked Booby mainly in the Caribbean.