Black Storm-Petrel

Oceanodroma melania

Order:
Procellariiformes
Family:
Hydrobatidae
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Black Storm-Petrel (20 July).

Large, all-dark, relatively long-winged and long-legged storm-petrel with prominently notched tail. Overall dark except for pale brown bar (wearing to grayish white) on upperwing extending transversely from lower scapulars across greater, median, and distal lesser wing coverts to just short of wrist, or bend of wing.

© Jeff Tingle , Puntarenas , Costa Rica , 20 July 2016
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Black Storm-Petrel (left) and Ashy Storm-Petrel (right).

Note that the Black Storm-Petrel (left) is larger and more chocolate-brown compared to the Ashy Storm-Petrel (right), which is smaller, grayer, and shows paler underwing coverts (not as evident as usual due to lighting), and has smaller tarsi and feet.

© Gary Nunn , California , United States , 10 June 2018
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Figure 2. Annual cycle of breeding, molt, and migration of the Black Storm-Petrel.

Nesting cycle is advanced in the Gulf of California. Compared to adults (shown), molt is advanced several weeks in subadults. The period of dispersal shown here includes both sub-adults and adults, the former dispersing a month or so earlier. Thick lines show peak activity; thin lines, off-peak.

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Black Storm-Petrel chick (22 July).

Chicks are covered in long, thick, grayish-brown down, which becomes lighter in appearance as chick expands in surface area.

© William Everett , Baja California , Mexico , 22 July 1989
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Juvenile Black Storm-Petrel (23 September).

Juvenile Plumage is similar in coloration to Definitive Basic Plumage, except that plumage is fresher than in adults in fall and winter, with thin fringing to the upperwing and underwing coverts more distinct. The evenly worn body feathering and wing coverts, the uniform look to the primaries and secondaries, and the brownish and narrow outer primaries and rectrices, suggests that this is a Juvenile.

© Nancy Christensen , California , United States , 23 September 2018
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Juvenile Black Storm-Petrel (28 August).

The evenly worn and brown plumage indicates a juvenile. One or two new, blacker back feathers are evident, indicating adventitious feather replacement or, perhaps, a Preformative Molt (see Molt).

© Curtis Marantz , California , United States , 28 August 2017
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Black Storm-Petrel likely undergoing Second Prebasic Molt (17 July).

Juvenile outer primaries and rectrices average narrower and become increasingly brownish and abraded through the first spring and summer with wear, as compared with basic feathers. Timing of molt can also assist with age; juveniles appear to molt primaries in April-July.

© Martin Reid , Oaxaca , Mexico , 17 July 2015
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Black Storm-Petrel undergoing Definitive Prebasic Molt (2 October).

In adults, complete molt occurs mostly away from breeding grounds, during non-breeding season, primarily October–March. Primary molt proceeds distally from p1 to p10. The broad and relatively dark and fresh outer primaries indicate that this bird is undergoing the Definitive Prebasic Molt but the early timing suggests a pre-breeding individual, perhaps 2-4 years of age.

© John van Dort , Valle , Honduras , 2 October 2015
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Black Storm-Petrel undergoing Definitive Prebasic Molt (7 December).

The Definitive Prebasic Molt has commenced, with the inner two primaries (p1-p2) on each wing having dropped. Note the 'molt clines' in the primaries, with outer feathers appearing fresher and darker, indicating a previous molt and that the older feathering if past of the Definitive Basic Plumage. The later timing to the commencement of this molt suggests that this was a successfully breeding adult the previous summer and fall.

© Michael Andersen , Lima , Peru , 7 December 2012
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Definitive Basic Black Storm-Petrel (20 August).

Entire body rich, dark, blackish brown; more sooty black dorsally, warm blackish brown ventrally. Head, neck, and mantle with slight plumbeous gloss when fresh. Upperwing coverts with transverse pale bar formed by broad buff-brown to pale brown outer edges to greater, median, and distal lesser coverts; bar does not reach forward to leading edge of wing. Remiges, primary coverts, and tail black, with rich fuscous tone; shafts to primaries pale at base, usually visible for short distance beyond tips of primary coverts. The broad blackish outer primaries and rectrices indicate Definitive Basic rather than Juvenile Plumage.

© Tom Benson , California , United States , 20 August 2016
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Definitive Basic Black Storm-Petrel (21 September).

Head, neck, and mantle with slight plumbeous gloss, creating darker appearance than rest of body feathering. Underwing coverts like belly, sometimes wood or even rusty brown, contrasting with black-brown border of wing.

© Brian Sullivan , California , United States , 21 September 2007
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Definitive Basic Black Storm-Petrel (2 October).

Transverse upperwing-covert bar can appear indistinct or nearly absent in some worn adults. Shafts to primaries pale at base, usually visible for short distance beyond tips of primary coverts.

© Brian Sullivan , California , United States , 2 October 2005

Large (length 23 cm, mass 60 g), all-dark (lacking white on rump or pale on underwing), relatively long-winged and long-legged storm-petrel with rather prominently notched tail. Sooty black dorsally, somewhat browner ventrally (especially wing-linings and belly, which may show tinge of rusty brown), plumage fading to browner with wear. Overall dark except for pale brown bar (wearing to grayish white) on upperwing extending transversely from lower scapulars across proximal greater, median, and distal lesser wing coverts to just short of wrist, or bend of wing. Bill, legs, and feet black; iris brown. Tarsus long (> 28 mm), being longer than middle toe with claw and twice as long as culmen. Wings long and angled; tail long and deeply notched (20 mm deep). Plumage similar among sexes and age classes; no change during the year (slight plumbeous gloss on head, neck, and mantle in fresh plumage only). Flight slow, deliberate, with deep wing beats interspersed with long glides; flight comparable to that of a Black Tern (Chlidonias niger) or nighthawk (Chordeiles spp.; 4, 5, 6). Will follow ships. See Behavior: Locomotion: Flight.

Similar Species

Very similar to Markham's Storm-Petrel (Oceanodroma markhami), with which Black Storm-Petrel overlaps at sea from Mexico south to northern Peru (7); see Distribution, Migration, and Habitat: Habitat in Marine Range. Identification of these two species in the field is problematic; see especially 8, 4, 9, 5, 10, 11, 12, 13, 6. Markham's Storm-Petrel is similar in body size, build, and dark plumage, although wing spread (48–53 cm vs. 49–54 cm for Markham's) and wing chord (163–181 mm vs. 164–181 mm in Markham's) average slightly longer for Markham's; tail is longer (77–94 mm vs. 85–111 mm in Markham's) and more deeply forked; bill is shallower (depth distal to tubenares 5.2–5.9 mm vs. 4.6–5.3 mm in Markham's), and legs much shorter (tarsus 29–34 mm vs. 23.9–25.0 mm in Markham's; see 12, 13. Pale bar on upperwing of Markham's Storm-Petrel usually extends to leading edge of wing, whereas this bar typically stops short of leading edge on Black Storm-Petrel. Markham's Storm-Petrel is overall paler and browner than Black Storm-Petrel, especially dorsally, but coloration varies with age and degree of plumage wear; e.g., wingbars are more prominent in worn plumage. Although of less value in the field, Markham's Storm-Petrel has uppertail coverts grayish basally with white shafts for half their length, unlike all-dark uppertail coverts on Black Storm-Petrel. Flight characteristics differ slightly. Flight of Black Storm-Petrel is distinctive, more direct, faster, and stronger, with deeper wing beats, and usually flies < 1 m above the ocean surface. By contrast, Markham’s Storm-Petrel often rises to > 1 m, in a more leisurely flight style (9, 5, 7, 6). Flight characteristics change with wind conditions and angle of bird to wind; glides become longer and wing beats deeper with higher wind speeds (14, 15, 16).

In the hand, Markham's Storm-Petrel is clearly separated on the basis of tarsus length (see above) and proportions (tarsus shorter than middle toe with claw and much less than twice as long as culmen; 8). Long tarsus and these proportional characteristics distinguish Black Storm-Petrel from two other large, all-dark Oceanodroma storm-petrels of the central and western Pacific—Tristram's (O. tristrami) and Matsudaira's (O. matsudairae). Matsudaira's Storm-Petrel is perhaps browner overall than Black Storm-Petrel, otherwise quite similar in the field. Although Matsudaira's Storm-Petrel is said to be distinctive among the four large, all-dark Pacific Oceanodroma in having prominent white shafts at base of outer primaries (e.g., 17, 18), this characteristic does exist (but less prominently, not extending as far out feather shafts) in Black, Markham's, and Tristram's storm-petrels. Tristram's Storm-Petrel further differs from Black Storm-Petrel in being grayer, especially on the head, and much larger (wing chord 182–192 mm, tail 92–114 mm, exposed culmen 16.8–19.5 mm), but with a shorter tarsus (26.6–30.4 mm) which is < foot with claws, legs thick and grayish (vs. thin and black in Black Storm-Petrel), and a less-pointed wing, with p10 shorter and usually < p7, as compared to p10 > p7 in Black Storm-Petrel (12).

Range overlaps broadly with three other storm-petrels that are all dark or have populations that are all dark: Ashy Storm-Petrel (O. homochroa), Least Storm-Petrel (O. microsoma), and Leach's Storm-Petrel (O. leucorhoa) (7). These are all significantly smaller than Black Storm-Petrel (12), especially Ashy and Least storm-petrels, which differ significantly in shape as well. Only the Leach's Storm-Petrel flies in a similar manner, i.e., long glides between several wing beats. Glides of Black Storm-Petrel are longer. Except in strong winds (i.e., more than about 45 km/h), when they can glide, the smaller storm-petrels flap almost continuously and remain in wave troughs (16). Downy chicks of these species are nearly indistinguishable from each other on islands where more than one species breeds; larger measurements of Black Storm-Petrel become useful as chick grows.

Detailed Description

The Black Storm-Petrel has 10 full-length primaries (numbered distally, p1 to p10; the tip of p10 falls 12–18 mm below that of p9 when fully grown, and is usually < p7 in length), 14 secondaries (numbered proximally, s1 to s11, and including 3 tertials, numbered distally, t1 to t3), and 12 rectrices (numbered distally, r1 to r6, on each side of the tail). Storm-petrels are diastataxic (see 19) indicating that a secondary has been lost evolutionarily between what we now term s4 and s5. Bill, legs, and feet black; iris brown. Tarsus long (> 28 mm), being longer than middle toe with claw and twice as long as culmen. Wings long and angled; tail long and moderately notched (20 mm deep). No geographic variation in appearance (see Systematics) or molt strategies have been reported.

Plumages

See Molts for molt and plumage terminology. The following is based primarily on detailed plumage descriptions of Loomis (20), Murphy (8), W. R. P. Bourne (in 18), Ainley (11), and Howell (6); see Pyle (12) for specific age-related criteria. Sexes show similar appearances in all plumages. Definitive appearance is essentially assumed at Juvenile Plumage, although definitive feather shapes are not obtained until Second Basic Plumage.

Natal Down

Present primarily July–October. Hatchlings with long, thick, grayish-brown natal down, very slightly darker above (8); a ball of fluff with a beak and feet sticking out. Face, chin, throat, top of head bare (apteria also bare). Darker, second down, appears at several days of age; becomes lighter in appearance as chick expands in surface area.

Juvenile (First Basic) Plumage

Present primarily October–August, assuming no Preformative Molt occurs (see Molts). Similar in coloration to Definitive Basic Plumage, except that plumage fresher than in adults in fall and winter, with thin fringing to the upperwing and underwing coverts more distinct. Juvenile outer primaries and rectrices also average narrower, and become increasingly brownish and abraded through the first spring and summer with wear, as compared with basic feathers. Timing of molt can alter with age; much of the time juveniles are in this plumage and not molting (October–March), older birds are in primary molt whereas Juveniles appear to molt primaries in April–July. Juvenile remiges are also grown at once and are consistent in wear, not showing 'molt clines' of later plumages (see below).

Definitive Basic Plumage

Present primarily October–September. Entire body rich, dark, blackish brown; more sooty black dorsally, warm blackish brown ventrally. Plumage darker when fresher in December–March, becoming browner when at breeding sites in March–September. Head, neck, and mantle with slight plumbeous gloss when fresh, often giving head a darker appearance than rest of body. Upperwing coverts with transverse pale bar formed by broad buff-brown to pale brown outer edges to proximal greater, median, and distal lesser coverts; bar does not reach forward to leading edge of wing; bar is variable and can appear indistinct or nearly absent in some worn adults. Remiges, primary coverts, and tail black, with rich fuscous tone; shafts to primaries pale at base, usually visible for short distance beyond tips of primary coverts. Underwing coverts like belly, sometimes wood or even rusty brown, contrasting with black-brown border of wing.

Definitive Basic Plumage distinguished from Juvenile Plumage by having broader, relatively fresher, and darker outer primaries and rectrices. Due to protracted molt, most subadults and adults are replacing primaries in November–March, after which "molt clines" are visible among primaries reflecting molt sequence (see below), primaries becoming darker and fresher distally, and the outermost secondary (s1) noticeably darker and fresher than the innermost primary (p1) due to a lag in the timing of replacement (12).

Aberrant Plumages

Among 220 specimens inspected by Baptista (21), 3.1% had at least 1 leucistic feather. Prevalence of such feathers is very low compared to 10 other storm-petrel species.

Molts

Molt and plumage terminology follows Humphrey and Parkes (22), as modified by Howell and Corben (23) and Howell et al. (24, 25). Black Storm-Petrel has been reported to exhibit a Simple Basic Strategy (cf. 24, 26), including complete prebasic molts, but no inserted preformative or prealternate molts (18, 27, 12, 26, 6; Figure 2). However, a limited inserted preformative molt of up to a few body feathers has been documented in some Procellariiformes (e.g., Great Shearwater [Ardenna gravis]; 28) and this could occur in Black Storm-Petrel as well (12). Most Procellariiformes with documented preformative molts are species that breed in the Southern Hemisphere and migrate to nutrient-rich waters in the Northern Hemisphere, whereas those that breed and/or molt in tropical or subtropical latitudes (including Black Storm-Petrel) may be less likely to have a preformative molt due to lack of available nutrients to first-cycle individuals (12). Study is needed.

Prejuvenile (First Prebasic) Molt

Complete, primarily July–October, in the nest burrow. As noted by Everett (1), first juvenile feathers to appear are the remiges and then the rectrices, which begin to emerge from sheaths about 6 wk after hatching. During week 6–8, first contour feathers emerge on the back and crown, during which time wings grow rapidly. Contour feathers are a continuation of the mesoptyle, which remains attached to tip of juvenile feathers, but soon wear off as they emerge. Breast-feathers emerge next, and contour-feather development progresses toward vent. By week 9–10, chicks usually fully feathered, except for traces of down remaining on vent and hindneck.

Second Prebasic Molt

Complete, probably primarily April–November. In the Gulf of Fonseca, Central America, Black Storm-Petrels observed molting primaries in May–June are consistent in timing with the Second Prebasic molt (29), as previously supposed (12, 6). Among 80 specimens taken at sea during July, 12 individuals had first primary just emerging and among 40 taken at sea late in August, 6 individuals had begun wing molt (20); these likely also undergoing Second Prebasic Molt. Flight-feather replacement sequence is similar to that of Definitive Prebasic Molt, but begins earlier and completes quicker due to lack of breeding constraints.

Definitive Prebasic Molt

Complete, primarily October–March (12, 6). In adults, complete molt occurs mostly away from breeding grounds, during non-breeding season. No evidence of wing molt, but some body molt late in summer, among 181 adults examined at colony, April–September (1, see also 20). Two adults off Panama in March in later stages of wing molt (8). Sequence like that of Ashy and Leach's storm-petrels (27): body molt begins first and completed slowly during wing and tail molt. Primary molt proceeds distally from p1 to p10; secondary molt proceeds from 2 centers: proximally from s1 proximally from s5 and bidirectionally from the second tertial (t2). The last feathers to complete growth are p10 and s4 and s9. Molt of rectrices also likely similar to that of Ashy and Leach's storm-petrels; commonly, rectrices are molted in pairs in the order 6 (outermost), 4, 2, 1, 3, 5 with much variation in the sequence.

Bare Parts

Bill and Gape

Black. Hatchling shows white egg tooth at end.

Iris

Brown at all ages.

Legs and Feet

Black at all ages.

Measurements

Linear Measurements

No known geographic, sexual, or age variation (see Table 2).

Mass

A sample of 112 adults nesting at Islas Coronado (near San Diego, California) during summer 1989 averaged 61.5 g ± 5.0 SD (range 53–77; 1). A second sample of 44 adults taken at sea, all months during the late 1960s, averaged 59.0 g ± 3.69 SD (range 50–67; 30). A sample of 360 adults breeding at Isla San Benito Oeste during August–October in 2012–2014 averaged 60.8 g ± 6.7 SD (range 47.3–85.1; Y. Bedolla-Guzmán, J. F. Masello, A. Aguirre-Muñoz, and P. Quillfeldt, unpublished data).

Recommended Citation

Everett, W. T., Y. R. Bedolla-Guzmán, and D. G. Ainley (2019). Black Storm-Petrel (Oceanodroma melania), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.bkspet.02