The largest colony of Leach's storm petrels can be found on Baccalieu Island off eastern Canada, an ecological reserve with ~1.95 million pairs of the birds at last estimate in 2013.

On the Atlantic Coast, separating this species from band-rumped storm petrels is difficult; identification involves characteristics such as the extent of white on the rump and flight pattern.

The bird was first photographed at the nest in 1958, on Eilean Mor, one of the Flannan Isles off the west coast of the Outer Hebrides in Scotland, by Jo Moran.

They feed primarily on plankton, including euphausiids, copepods, and a form of amphipod that is parasitic to jellyfish gonadal pouches.

They also feed to a large extent on myctophids (lantern fish), which only occur at the surface at night in water over the continental slope.

[9] A breeding individual stores energy-rich lipids in a sac anterior to its stomach, which is used to either sustain itself while incubating its single egg, to feed its chick, or as a defensive mechanism when caught by a predator, as do many other Procellariformes.

Parent birds also accidentally feed their chicks plastic debris, which they mistake for food items floating on the surface of the ocean.