The bulge on this little seabird represents precious cargo. It came as a surprise to researchers floating patiently in the Indian Ocean off the coast of Réunion—the only breeding site of the critically endangered Mascarene petrel (Pseudobulweria aterrima). The team periodically hoisted overboard 23-kilogram blocks of frozen fish and fish oil: bobbing bait that slowly melted into an enticing, oily slick. Among the visitors were 33 of the dwindling and little-studied birds, 12 of which were caught on camera—the first photos of the species taken at sea. The views offer unprecedented evidence of the seabird’s subtle distinguishing features, but this shot wasn’t so subtle: a female with a bulbous lump on her belly, the first document of any bird flying while obviously bearing an egg, the researchers report in the latest issue of the Bulletin of the British Ornithologists' Club. It’s also the first evidence of the Mascarene petrel’s return from its “prelaying exodus,” where it builds up fat reserves before incubating. And it adds to scientific knowledge about the petrel’s breeding cycle: It was taken on 22 December, whereas previous observations found that the species—of which an estimated 100 breeding pairs remain—usually lays its eggs in late October and November.