It breeds on inaccessible islands in the colder northern areas of the Atlantic and Pacific. It nests in colonies close to the sea in well concealed areas such as rock crevices, shallow burrows or even logs. It lays a single white egg which often has a faint ring of spots at the large end. This storm-petrel is strictly nocturnal at the breeding sites to avoid predation by gulls and skuas, and will even avoid coming to land on clear moonlit nights. The largest colony of Leach's Storm-petrels can be found on Baccalieu Island of eastern Canada, an ecological reserve with more than 3 million pairs of the bird.
The Leach's Petrel, known in some rural areas as Carrie Chicks, is a small bird at 18–21 cm in length with a 43–48 cm wingspan, but is distinctly larger than the European Storm-petrel, which it superficially resembles with its dark plumage and white rump. It has a fluttering flight, and patters on the water surface as it picks planktonic food items from the ocean surface. It can be distinguished from the European Storm-petrel by its larger size, forked tail, different rump pattern and flight behaviour. Some north-eastern Pacific Leach's Petrels show all-dark rumps. Like most petrels, its walking ability is limited to a short shuffle to the burrow. One interesting aspect of the bird is that contrary to most species, this bird gains telomere growth as they grow older. Telomere shortening in cell division limits the maximum lifespan of most other species. The lifespan of the Leach's Petrel is therefore theoretically limitless. This is a matter of debate, however. Studies have shown that while the telomere growth may have contributed to the eldest of specimens, young specimens exhibit telomeres that are longer, and shorten over time. The leach's Petrel lifespan may be inconclusive, but there is no data to support the hypothesis that this species is possibly immortal.
Distribution and habitatEdit
It is strictly pelagic outside the breeding season, and this, together with its remote breeding sites, makes Leach's Petrel a difficult bird to see from land. Only in storms might this species be pushed into headlands. Unlike Storm-petrel, it does not follow ships. In Europe, the best chance of seeing this species is in September in Liverpool Bay between north Wales and England. Strong north-westerlies funnel migrating Leach's Petrels into this bay.