Christmas Shearwaters often forage in large, mixed-species flocks that are associated with schools of large predatory fish, which drive smaller prey to the surface. They feed from the surface by seizing prey while sitting on the water or engaging in shallow pursuit plunges. Additionally, they can dip or pick prey from the water while in flight. Their diet is nearly evenly divided between fish and squid from the Ommastrephidae family.

Like many seabirds, Christmas Shearwaters breed in their natal colonies. However, these colonies tend to be small, and the birds exhibit high site fidelity. They lay only one egg per season, and both parents are involved in all aspects of raising their young.

Christmas Shearwaters typically nest in rock crevices or under dense vegetation. In Hawai‘i, they begin laying eggs in February, with nestlings fledging in October or November. No post-fledging care is provided, and based on a small sample, the average age of first breeding is four years. The oldest known Christmas Shearwater lived to be 17 years old.

Christmas Shearwaters breed in colonies on islands located in tropical and subtropical areas of the Pacific Ocean. In the Hawaiian Islands, nesting occurs on offshore islets of the main islands, specifically Ka‘ula, Moku Manu, and Lehua, as well as in the Northwestern Hawaiian Islands, ranging from Nihoa to Kure Atoll, excluding Necker Island and Gardner Pinnacles.

Separate populations can be found breeding on Johnston Atoll, Ducie and Oeno Islands in the Pitcairn Islands, Sala y Gómez in Chile, Motu Nui (Easter Island), and throughout the Marquesas, Tuamotu, Line, Phoenix, and Austral island groups. Aside from the populations in the Hawaiian and Line Islands, little information is available regarding breeding populations in the rest of the species’ range. This species has been extirpated from the Ogasawara Islands, Minami Torishima, and Wake Island in the western Pacific.

The total estimated breeding population in the Hawaiian Islands ranges from approximately 2,500 to 3,300 pairs. The largest breeding colony in the archipelago, consisting of about 1,500 to 2,000 nesting pairs, is located on Laysan Island.

Introduced Predators: Like all seabirds, adults and their nests are vulnerable to predation by rats (Rattus spp.) and feral cats (Felis silvestris). Fortunately, all sites in the Northwestern Hawaiian Islands (NWHI) are free from both rats and cats.

Invasive Species: On Lisianski and Laysan Islands, rabbits (Oryctolagus cuniculus) have severely reduced suitable nesting locations by denuding the vegetation. Additionally, Golden Crown-beard (Verbesina encelioides) further degrades these crucial nesting habitats. At Kure, introduced Big-headed Ants (Pheidole megacephala) may contribute to nestling mortality and facilitate the destruction of native vegetation by supporting a non-native scale insect.