Leach's Storm-Petrel

Overview

Leach's Storm-Petrel is a small tubenose known for its bounding, erratic flight over open water, quite different from the fluttering pattering flight of some smaller relatives. It nests in burrows on remote, often forested or grassy islands and visits colonies only under cover of darkness.

It is larger than the European and Wilson's Storm-Petrels and shows a distinctly forked tail along with a pale band across the upperwing coverts, both useful clues when examining feathers or wing fragments.

Leach's Storm-Petrel feathers are somewhat larger than those of the smaller storm-petrel species and show more contrast on the upperwing.

• Upperwing coverts: A pale grayish-brown bar crosses the coverts, standing out against the darker surrounding feathers; this carpal bar is a key distinguishing feature from smaller relatives.
• Rump and tail: Rump feathers are white, sometimes with a dark central line dividing the white patch depending on population; tail feathers are notably forked rather than square.
• Body feathers: Overall sooty brown-black, similar in tone to other storm-petrels but on a larger feather base.
• Compared to European and Wilson's: Larger size, a forked tail, and the pale upperwing bar separate Leach's feathers from the smaller, more uniformly dark feathers of its relatives.

Adults are sooty blackish-brown overall with a white rump patch (occasionally divided by a dark central line in some populations) and a pale tan-gray bar across the upperwing coverts. Sexes look alike. Juveniles resemble adults closely. The complete molt takes place primarily outside the breeding season, timed around the bird's long migratory movements.

Leach's Storm-Petrels breed in burrows on remote islands across the North Atlantic and North Pacific, often in vegetated or soil-covered terrain suitable for digging. After breeding, they disperse widely across open ocean, with some populations undertaking long migrations into the Southern Hemisphere. They are almost entirely pelagic outside the breeding season and rarely seen from shore except during storms.

This species feeds over open water, picking small fish, invertebrates, and oily matter from the surface using a more bounding, unpredictable flight style than the steadier fluttering of smaller storm-petrels. Nesting burrows are visited only at night to reduce predation risk from gulls and other avian predators, with a single egg laid and long incubation shared by both parents. Calls include a distinctive chattering or purring song given at the nest, often described as an eerie, rhythmic sound heard from underground burrows after dark.