Kermadec Petrel vs Soft-plumaged Petrel

In short

The most reliable field mark between Kermadec Petrel and Soft-plumaged Petrel is overall structure and plumage contrast in flight: Kermadec Petrel is noticeably larger and bulkier, with variable plumage (including all-dark morphs), while Soft-plumaged Petrel is slimmer, with a distinctive dark grey-and-white pattern, pointed tail, and narrow wings. Soft-plumaged Petrel shows a striking white face with dark eye patch and mostly white underparts, contrasting with darker underwings—features not matched by any Kermadec Petrel morph. Both species can show dark morphs, but Kermadec's polymorphism is more extensive and can lead to confusion. Careful attention to size, shape, and face pattern is key, especially in flight.

Identification tips

1. Size and bulk: Kermadec Petrel is much larger and heavier than Soft-plumaged Petrel; use this when birds are seen together or with known species for scale.
2. Wing and tail shape: Soft-plumaged Petrel has narrow wings and a pointed tail, especially obvious in flight; Kermadec Petrel is broader-winged and less pointed.
3. Face pattern: Soft-plumaged Petrel shows a striking white face with a dark eye patch and white throat, visible even at distance; Kermadec Petrel (all morphs) lacks this combination.
4. Underpart contrast: Soft-plumaged Petrel has mostly white underparts with dark underwings; Kermadec Petrel's underparts vary from all-dark to pale but never show the same crisp white face and belly with dark underwing contrast.
5. Polymorphism: Kermadec Petrel is highly variable (light, dark, intermediate), so beware of dark morphs; Soft-plumaged is less variable, and its dark morph usually retains some white on the face or throat.
6. Bill: Soft-plumaged Petrel's bill is black, 25–32 mm, with a sharp hook; Kermadec's bill is proportionally larger and heavier, but this is rarely diagnostic at sea.
7. Legs: Soft-plumaged Petrel has pink legs with black on the outer webs and toes; this is rarely visible in the field.
8. Flight style: Kermadec Petrel flies with slower, more powerful wingbeats; Soft-plumaged is more buoyant and agile, with quicker flicks and a more tern-like jizz.
9. Tail in flight: The pointed tail of Soft-plumaged Petrel is a good field mark; Kermadec's tail is less pointed.
10. Plumage pitfalls: Dark morph Soft-plumaged can be confused with intermediate Kermadec, but look for face contrast and size.
11. Geographic context: If near Kermadec Islands or Lord Howe, consider Kermadec Petrel; in subantarctic waters, Soft-plumaged is more likely.
12. Vocalizations: If you hear medium-pitched moans and shrill squeaks, Soft-plumaged Petrel is more likely; Kermadec's voice is not described here.
13. Perched birds: Kermadec Petrel appears bulkier and more robust; Soft-plumaged is slimmer.
14. Group composition: If with other Pterodroma petrels, compare size and face pattern for best separation.
15. Age/season: No age-specific upperwing or juvenile marks are described for either species, so rely on adult and general plumage and structure.

Size

Kermadec Petrel is substantially heavier (501 g vs 300 g) and longer (38 cm vs medium-sized for Soft-plumaged), with a broader wingspan (100 cm). In the field, Kermadec appears bulkier and more powerful, while Soft-plumaged Petrel is noticeably slimmer and more delicate. When seen together, Kermadec's larger size and heavier build are evident, but beware of lone birds where size can be hard to judge.

Plumage

No age-specific upperwing patterns are described for either species, so focus is on adult and general plumage. Kermadec Petrel is highly variable: it can be light, dark, or intermediate, with some birds appearing entirely dark above and below, others pale below, and all combinations in between. Soft-plumaged Petrel is less variable, usually showing a dark grey head with a white face and throat, a dark eye patch, and white speckling on the forehead. Its underparts are mostly white, with contrasting dark grey underwings. In flight, Soft-plumaged Petrel's narrow wings and pointed tail are distinctive, and the face pattern is often visible even at a distance. Both species can show dark morphs, but Soft-plumaged's dark morph is less common and still tends to show some face contrast. Kermadec's all-dark morph lacks the white face and underpart contrast of Soft-plumaged.

Behaviour

Both are pelagic petrels with similar flight styles, but Kermadec Petrel's larger size gives it a heavier, more powerful flight, while Soft-plumaged Petrel is more buoyant and agile, with quicker, more flickering wingbeats. The pointed tail of Soft-plumaged is often visible in flight, adding to its distinctive jizz. Perched, Kermadec Petrel appears bulkier and more robust, while Soft-plumaged is more slender.

Habitat

Both species are oceanic and rarely seen from land except near breeding sites. Kermadec Petrel is much more restricted in range, breeding on a handful of islands in the southwest Pacific and appearing as a rare vagrant elsewhere. Soft-plumaged Petrel is more widespread in the southern oceans. If seen near Lord Howe or the Kermadec Islands, Kermadec Petrel is more likely, while Soft-plumaged is more expected in subantarctic waters.

Voice

Soft-plumaged Petrel is described as noisy, with medium-pitched moans and shrill squeaks. No vocal description is provided for Kermadec Petrel in the available notes, so voice is not a reliable separator unless Soft-plumaged's calls are heard.