Leach’s Storm Petrel
Scientific Name: Oceanodroma leucorhoa
Description
This, the commonest, and yet the most mysterious of our island’s residents, is the major focus of the Island Research Center’s current research. Julia Ambagis estimated that 9297 +/- 6500 pairs of petrels nested on Great Duck in 2000. A more recent re-analysis of Julia’s work suggests that the actual number may lie around 5000 pairs, well within her range of estimates. More recent estimates have ranged from 5000 to a high of over 20,000 pairs, which is hard to believe. In any case, this makes Great Duck the largest petrel colony in the eastern US.
According to some stories, Petrels — also referred to as “Mother Carey’s Chickens” — get their name from St. Peter’s ability to walk on the waves. Strictly speaking petrels don’t “walk” on water, but they dabble their feet while fluttering over the surface, stirring up plankton, which they then swallow and process into a protein-rich oil, which also gives their burrows a pleasant musky odor.
Petrels are not strictly nocturnal — they forage in daylight up to 200 miles off-shore, and can frequently be seen on foggy days in in-shore waters. Their habit of appearing along the coast immediately before bad weather is responsible for the “storm” component of their name. They only come in to the breeding colony after dark — usually between 10 p.m. and 4 a.m. They nest in shallow burrows that run 25 cm to over 1m in length and lay a single egg. Because both members of a pair may be away at sea for prolonged periods, the egg tends to be cooler than that of actively brooding species, and incubation takes much longer than in gulls or guillemots.
We have found petrel chicks in burrows as late as October, hence the reason for Great Duck’s closure to visitation until mid-Autumn. Major predators on petrel adults, eggs, and chicks seem to be crows and ravens, who excavate burrows and devour whatever they may find.