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Swinhoe's Storm Petrel | Hydrobates monorhis
Chinees stormvogeltje | Paíño de Swinhoe
Swinhoe's Storm Petrel is a small, uniformly sooty-brown storm petrel with a forked tail, breeding on islets off China, Korea, Japan and the Russian Far East and spending the rest of the year in the northern Indian Ocean. In the waters of this guide it is a rare vagrant, and what marks it out is mostly what it lacks: no trace of white on the rump, none on the belly, only a paler diagonal band across the upperwing.
Voice
At sea it is silent, and since every Australian record comes from deep water, voice is of no use to the user of this guide. At the East Asian colonies, which it visits only in darkness, a low purring arrr-r-r-r-r rolls out of the burrows with a stutter halfway through, and birds in flight over the colony give a short, shrill chi-chik. Away from the colony the species is all but mute.
No freely licensed recording has been found for this species yet; what to listen for is described below.
Identification
Eighteen to twenty-one centimetres, with a wingspan of a little over forty-five: long, narrow wings kinked at the carpal, and a clearly forked tail. The plumage is plain blackish brown, the only marking a paler grey-brown diagonal bar across the upperwing coverts running from the carpal in towards the body. The rump is dark, and that one point disposes of most other storm petrels in this area at a glance. At close range the pale shafts at the base of the outer primaries show as a faint light streak. The feet do not project beyond the tail. Flight is strong and erratic, with deep beats and shearing, banking glides — not the bouncing, pattering action of the Oceanitidae.
Confusion species
Matsudaira's Storm Petrel (Hydrobates matsudairae) is the real problem: equally dark, equally fork-tailed, but at twenty-four to twenty-five centimetres a quarter larger, with a slower, heavier wingbeat and with conspicuously white shafts forming a pale patch at the base of the primaries — in Swinhoe's that never amounts to more than a thin streak. Wilson's Storm Petrel (Oceanites oceanicus) and Band-rumped Storm Petrel (Hydrobates castro) both show a white rump and a far shallower tail fork. Bulwer's Petrel (Bulweria bulwerii) is larger, with a long wedge-shaped rather than forked tail, and shears low over the water on bowed wings. Be honest about the limits: a dark storm petrel at range in Australian waters often cannot be named at all, and virtually every accepted record rests on photographs.
Habitat
Open ocean over deep water well beyond the shelf, where it picks small crustaceans, squid and oily scraps from the surface and favours upwellings and temperature fronts. It touches land only at the colony, on rocky islets in the north-west Pacific, nesting in a cavity under boulders or in turf. Within this guide it is a bird of the open sea and nothing else.
Where the bird is most often found, arranged by main group and formation.
Range and movements
Within this guide's map window a vagrant only. The measurement made for this guide (GBIF, the ten full years 2015–2024) yields thirty-eight records, all in Australian waters and spread over five of those ten years; there is no record from New Zealand or Norfolk Island. That fits the species' non-breeding range in the northern Indian Ocean: records are chiefly to be expected in the western half of the window, on trips that run out from Western Australia into deep water. The colonies lie thousands of kilometres to the north.
Where and when to look
Do not look for it from land. The chance comes on a pelagic trip far enough offshore to reach deep water, and even then it means checking every dark storm petrel behind the chum. Take the rump first (dark, not white), then the tail (clearly forked), and only then size, which is notoriously unreliable at sea. Photograph what you see; this identification is nearly always settled afterwards on the images.
Conservation
Near Threatened (NT), uplisted from Least Concern in 2012. The largest known colony holds some seven and a half thousand pairs on Verkhovsky Island near Vladivostok; there are at least a thousand pairs in Japan and smaller numbers in China, Taiwan and on the Korean peninsula. The IUCN expects a moderately rapid decline over three generations, driven mainly by introduced mammals on the breeding islets — rats taking eggs and chicks, and feral cats. Fisheries bycatch, light pollution near colonies and plastic in the diet add to it. None of this produces a measurable trend in Australian waters, where the bird is far too scarce for that. But a vagrant grows rarer as its source population shrinks.
Scientific name
Hydrobates monorhis | (Swinhoe, 1867)
Robert Swinhoe, British consul on the China coast and the foremost collector of Chinese birds of his day, described the species in 1867; because it has since been placed in Hydrobates, author and year stand in parentheses. The epithet monorhis is from Greek monos, 'single', and rhis, 'nose', and points to the nostril tube on top of the bill, which in this family projects as one tube rather than two separate ones. The type locality lies in the Chinese coastal waters where Swinhoe worked. The English and Spanish guide names keep his name; the Dutch one points instead to the breeding range.