Seabird in the Cretaceous, with a species called "Tytthostonyx glauconiticus", which seems allied to the Procellariiformes and Pelecaniformes. In the Paleogene both pterosaurs and marine reptiles became extinct, allowing seabirds to expand ecologically. These post-extinction seas were dominated by early Procellariidae, giant penguins and two extinct families, the Pelagornithidae and the Plotopteridae (a group of large seabirds that looked like the penguins). Modern genera began their wide radiation in the Miocene, although the genus "Puffinus" (which includes today's Manx shearwater and sooty shearwater) might date back to the Oligocene. The highest diversity of seabirds apparently existed during the Late Miocene and
Ilhéus do Rombo Cima is famous for its seabird colonies. Ilhéu Grande, which has been used by goat farmers and whalers in the past, does not currently support breeding seabirds, though large colonies must have existed formerly as the island has thick layers of guano. The island group has been identified as an Important Bird Area (IBA) by BirdLife International because it supports seabird colonies as well as peregrine falcons and Iago sparrows. Birds include the Frigate bird ("Pelagodroma marina") numbering around 1,000 in 1989, the Boyd's shearwater ("Puffinus boydi"), "Oceanodroma castro", Bulwer's petrel ("Bulweria bulwerii"), the brown booby ("Sula leucogaster") (50 pairs