How to Identify Leach's Storm-Petrel Feathers

What Leach's Storm-Petrel Feathers Look Like

Leach's Storm-Petrel is a small, sooty seabird that spends nearly its entire life over open ocean, coming to land only to nest in burrows on remote islands. Its feathers are compact but show a few very specific diagnostic features.

• Body/contour feathers: Overall sooty brown to blackish, with no bright colors.
• Wing covert feathers: A pale buffy-tan diagonal bar crosses the upperwing coverts, standing out against the darker surrounding feathers — a useful clue if found isolated.
• Rump feathers: White, but often with a thin dark central line dividing the white patch into two halves — this partial division is a key diagnostic detail.
• Tail feathers: Distinctly forked, with the central feathers notably shorter than the outer ones, unlike the square or rounded tail of some similar species.
• Size: Small overall; flight feathers typically under 6 inches (15 cm), reflecting the bird's small, swallow-like build.

Step-by-Step: Is This Feather From a Leach's Storm-Petrel?

1. Check overall color. Uniform sooty-brown to blackish, without bold patterning aside from the wing bar and rump, fits storm-petrels generally.
2. Look for a pale buffy wing-covert bar. A tan diagonal band on an otherwise dark covert feather supports this species.
3. Inspect the rump feathers for a white patch with a dark central line. A divided or partially interrupted white rump is more consistent with Leach's than a fully white, undivided rump.
4. Check tail feather shape. A forked shape, with shorter central feathers, is a strong clue; a square-ended tail feather suggests a different storm-petrel (see below).
5. Consider the finding location. Offshore waters and remote nesting islands in the North Atlantic and North Pacific fit this species' range; a beach find after a storm is also plausible given its pelagic habits.

Similar Species & How to Tell Them Apart

• Wilson's Storm-Petrel: Has a square (not forked) tail, and its white rump patch fully wraps around to the undertail without a dividing dark line — tail shape and rump completeness are the best separators.
• Band-rumped Storm-Petrel: Shows a broader, more solidly white rump band without the central dark line, and a less deeply forked tail than Leach's.
• Ashy Storm-Petrel (Pacific): Overall grayer-brown rather than sooty-black, and typically lacks a bright white rump patch at all.
• Fork-tailed Storm-Petrel: Overall pale gray rather than dark sooty-brown, a clear color difference from Leach's.

Where & When You'll Find Them

Leach's Storm-Petrels nest in burrows on remote islands across the North Atlantic and North Pacific, spending the rest of their time far out at sea, often well beyond sight of land. Because of this pelagic lifestyle, feathers are most likely to be found either near breeding colonies during the nesting season (roughly May through September, depending on the colony) or washed up on beaches following strong onshore storms that push offshore birds toward the coast at other times of year.