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Audubon's Shearwater Puffinus lherminieri Scientific name definitions

Guy M. Kirwan, Carles Carboneras, and Francesc Jutglar
Version: 1.0 — Published March 4, 2020

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Introduction

This seabird is characterized by its largely black upperparts and white underparts, and is not unlike the generally more familiar Manx Shearwater (Puffinus puffinus). Until recently, some ten subspecies of the Audubon’s Shearwater were generally recognized, distributed throughout much of the world’s tropical oceans. However, their taxonomy has been heavily debated over the course of the last couple of decades, and considerable systematic rearrangement is now generally accepted, especially as a result of vocal and molecular research. As currently constituted, Audubon’s Shearwater is now considered to comprise just two subspecies, both of which are largely or wholly confined as breeding birds to the Caribbean region, with the exception of populations, provisionally assigned to this species, nesting on islands off eastern Brazil. A third Neotropical taxon, long united with the present species, is now also recognized at species level, namely Galapagos Shearwater (Puffinus subalaris). The latter population is distinctly unusual in that the birds are strictly diurnal, never flying around their colonies by night.

Field Identification

27.0–36.2 cm; 138–290 g (1, 2, 3); wingspan 64–74 cm (1). Small, dark-and-white shearwater with comparatively short broad wings and long rounded tail. May recall miniature Wedge-tailed Shearwater (Ardenna pacifica ); present species marginally smaller than Manx Shearwater (Puffinus puffinus), with comparatively broader and rounded wings, dark undertail coverts, underwing usually less extensively white on coverts, often with more white on face or around eye (depending on races), usually with faster fluttering flight. Most similar to marginally smaller but allopatric Little Shearwater (Puffinus assimilis), with more gliding component in flight and slower wingbeats, but is proportionately smaller, with less rounded head, slim body, slightly larger or longer bill, and especially broader dark edgings to underwing; some races have brown cast on upperparts and most have plain upperwing, while dark undertail coverts are key character. Sexes similar, but female averages slightly smaller in most measurements.

Similar Species

The following is based almost entirely on Howell (4). Other species which might be expected in the same waters as the present species include:

Manx Shearwater (Puffinus puffinus). In structure, is slightly larger and stockier than typical individuals of Audubon’s Shearwater, with relatively longer, narrower, and more pointed wings, a shorter tail (with white undertail coverts), a shorter neck, and higher wing-loading. In typical flight, Manx appears stronger and more confident in flight, gliding less buoyantly on slightly bowed wings in calm conditions or light winds, and wheeling high and steeply in moderate to strong winds, as opposed to which the present species always tends to fly closer to the sea surface and to perform shallower arcs. However, some experience (of both species) will be necessary to correctly evaluate these characters. In morphology, Manx typically appears rather black-faced, with a whitish hook behind the dark ear-coverts, whereas Audubon’s is overall white-faced with a shallower, and cleaner-cut, dark cap, often with whitish spectacles. Those populations of the present species with, on average, darker-looking faces, also have the blackest undertail coverts, e.g. in the Lesser Antilles. Note, however, that at rest Audubon’s can appear rather white-vented, but the undertail coverts are always black, at least distally, whereas Manx is always white in this region, but does have a black thigh patch, which can appear to invade the ventral region. Although Manx typically has blacker, more slaty-blackish upperparts, versus browner in Audubon’s, in regions and seasons where the two species might be seen together, i.e., in the western Atlantic in May–September, first-year Manx are faded and appear more brownish above, and one must also take into account the effects of lighting. The underside of the primaries of Manx is dark gray, often reflecting as silvery, but solid black in Audubon’s, thus the underwing of Manx usually appears much paler, especially on the leading edge, whereas that of Audubon’s has broad dark margins. On the water, Audubon’s appears to have a longer rear end, with the tail projecting beyond the wingtips, whereas in Manx the rear seems more truncated, and the wings project very slightly past the tail end.

Barolo Shearwater (Puffinus baroli). Not definitely recorded in breeding range of Audubon’s Shearwater, and at most probably a very rare visitor to eastern North American waters. In terms of general structure, this species is smaller, with a shorter bill, and shorter tail (beware Audubon’s in molt, August–October), usually faster and more hurried flight, on quicker wingbeats, with shorter glides, although bear in mind that these last features are strongly affected by wind direction and speed, and the bird’s behavior. Also note that such differences are only likely to be apparent in direct comparison, and that prior of experience of both species will be extremely useful in making such analyses. Barolo has white undertail coverts, and the underwings generally appear whitish to slate-gray, with a variable blackish trailing edge, although the darkest birds can approach Audubon’s. The upperparts of the present species are blacker, at least in fresh plumage (May–January), while the black cap extends to the upper edge of the eye (but reaches its lower edge in Audubon’s). Overall, Barolo appears even more white-faced than Audubon’s, with the eye standing out in the face. In fresh plumage (May–February), adult Barolo shows whitish tips to the median and greater coverts, and can appear to show a pale trailing edge to the wing at these times. Finally, the legs and feet of Barolo are typically grayish blue, not pinkish as in Audubon’s.

Boyd’s Shearwater (Puffinus boydi). This species has not definitely been recorded in North America, but could potentially occur. Its plumage, structure, and flight behavior are closest to those of Audubon’s, among the three species discussed here, but is smaller overall, and shows on average more white around the eyes (including behind them, whereas in whitest-faced Audubon’s the majority of white feathering is forward of the irides), and the legs and feet are grayish blue in general.

Plumages

Juvenile

Juvenile as adult, but young are typically in fresh plumage in May–August, when older birds are either worn or molting (1).

Adult

Adult has cap to eye and rest of upperparts including upperwing and tail fairly uniform blackish brown to dark gray-brown, usually with some whitish around eye (partial eye ring and sometimes a short fore superciliary or narrow and short posterior eyestripe); brown-gray on sides of breast less sharply demarcated from white underparts but often extends to form a partial breast-band, thighs and undertail coverts dark brownish, rest of underparts white, extending up to form conspicuous spot at sides of rump; underwing has broad dark gray trailing edge (exposed remiges), bases of primaries usually have small amount of silvery white so outer wing may show less contrast between dark margin and mostly white coverts, very narrow dark leading edge formed by marginal coverts, the lesser coverts variably marked with dark spots or streaks, especially on carpal area and ‘elbow’, the latter may have rather solid large dark patch, with some dark at anterior base of wing, but axillaries white, greater coverts can be dark.

Molts

Very little published information. Adults off eastern North America in late June and July are commencing wing molt, and are completing this replacement in late September and October, while tail molt occurs mainly in September and October; second pre-basic wing molt starts mainly in May and June, and is usually completed by August (4). Timing in other (Caribbean) populations is basically unknown, but is thought to be probably similar, given that breeding schedules are broadly concordant (4), although this may not be true for those nesting on islands off eastern Brazil.

Bare Parts

Bill and Gape

Bill grayish or blue-gray, often duskier on culmen and blacker at tip, with blackish tubes.

Iris

Irides dark brown.

Legs and Feet

Legs and feet pale pink, with outer side of tarsus and outer toes variably tinged dusky or blackish. Some birds, however, have the legs and toes bluish with pinkish webs, and these are thought to be juveniles (5, 4).

Measurements

Linear Measurements

Measurements in mm, from Howell (4), Brazilian specimens from Soto and Filippini (2) and Macedo Mestre et al. (3):

Nominate race (n = 20) P. l. loyemilleri (n = 11) Brazil (n = 7, unless otherwise stated)
Wing chord 192–210 185–195 208.0–211.3
Tail length 83–91 81–88 90–93 (n = 4)
Bill length 27–32 27–31 28.2–30.4
Tarsus length 39–42 38–40 41.0–45.4 (n = 19)

Systematics History

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Treated by Carboneras (6) as comprising ten subspecies including what are now Tropical Shearwater (P. bailloni), Persian Shearwater (P. persicus) and Bannerman’s Shearwater (P. bannermani), but Barolo Shearwater (P. baroli) and Boyd’s Shearwater (P. boydi) were then treated as subspecies of Little Shearwater (P. assimilis). Recently, P. baroli and P. boydi have been split from P. lherminieri as either one species (7) or as two species (8), while in a third treatment P. baroli was split from P. lherminieri and P. boydi (9). Given that the various points of morphological similarity and divergence in these taxa compose a mosaic of half-shared characters, a recent molecular analysis (10) identified a clade involving P. lherminieri, P. baroli, and P. boydi, and these three taxa are geographically grouped together in the North Atlantic, del Hoyo and Collar (11) opted to retain them as one species, with race loyemilleri (breeding on islands off northwest Panama) being treated as a synonym of the nominate (10), but here all three are considered to represent separate species.

Geographic Variation

Most birds nesting in the Bahamas have the basal 25–65% of the undertail-coverts white, but at least some that are believed to breed in the Lesser Antilles have almost solidly blackish undertail-coverts (4). Axillaries vary from overall white to having variable dusky markings, but at present there is no known geographic component to this variation (4). Those populations breeding on islets off northern Panama and northern Venezuela are, in plumage, not considered different from the nominate, but are on average smaller (12, 4), and have been named as a separate subspecies, loyemilleri (13). Some authors (14) have attributed those nesting on Isla Providencia (which is Colombian territory) also to loyemilleri, and have also deemed Venezuelan populations to be either intermediates or of unknown racial identification. Those nesting off eastern Brazil have been said to closely resemble loyemilleri (2), but mensurally they appear larger than either of the described subspecies, although available samples are still very small (see Measurements).

Subspecies

Two subspecies recognized. Subspecific attribution of populations breeding off eastern Brazil currently uncertain (see Geographic Variation).


SUBSPECIES

Puffinus lherminieri lherminieri Scientific name definitions

Distribution

P. l. lherminieri Lesson, 1839: tropical and subtropical western Atlantic Ocean, breeding in the Bahamas, West Indies, islets east of Nicaragua (Providencia Island), and islets off northern Venezuela (Islas Los Roques, Isla Orchila, Islas Los Hermanos); formerly also on Bermuda.


SUBSPECIES

Puffinus lherminieri loyemilleri Scientific name definitions

Distribution

P. l. loyemilleri Wetmore, 1959: breeds on islands off northwest Panama (Bocas del Toro archipelago).

Related Species

Apparently is most closely related to P. baroli and P. boydi (5).

Nomenclature

The specific name lherminieri immortalizes the French naturalist Félix Louis l’Herminier (1779–1833), who acquired the type specimen while stationed in Guadeloupe. Subspecies loyemilleri was named by Alexander Wetmore (13) in honor of the US palaeornithologist Loye Holmes Miller (1874–1970).

Distribution

Occurs in the tropical and subtropical western Atlantic Ocean, breeding in the Bahamas, the West Indies, islets east of Nicaragua (Providencia Island), and islands off northwest Panama. Tiny populations, provisionally ascribed to this species, are also known from Fernando de Noronha and the Itatiaia Islands, off eastern Brazil.

Historical Changes to the Distribution

Formerly also occurred on Antigua, Bermuda (15), and Ascension Island (16).

Habitat

Marine; normally in offshore waters, but also pelagic and near land in vicinity of colonies.

Habitat in Breeding Range

Breeds on oceanic islands, and rocky offshore islets, occupying cliffs and earthy slopes, usually with little more than herbaceous vegetation, or in rock crevices, among rubble, and in burrows dug in soil (4).

Migration Overview

Little known. Adults thought to be largely sedentary; immatures probably more dispersive. Regular movements suspected in northwest Atlantic, where it is regularly (but perhaps decreasingly) recorded in the period late April–November (peaking June–September, much rarer to January) in waters between Florida  and North Carolina, with even rarer records further north to southern New England, even southern Nova Scotia (late June–September, mainly July/August), with occasional inland records (exceptionally as far as Kentucky and Ontario, the latter perhaps race loyemilleri 17), uncommon to locally fairly common in Gulf of Mexico (April–November, mainly August/September) and birds ascribed to race loyemilleri recorded year-round from Costa Rica east to Venezuela, and rarely to Guyana (12, 18, 1), Suriname (19) and French Guiana (20). Has even been suggested that it might have reached Britain (21), although there are no accepted records.

Feeding

Main Foods Taken

Mainly fish, squid, and crustaceans.

Microhabitat for Foraging

Sometimes joins other feeding seabirds, including other shearwaters, terns, and boobies, and is often seen in the same sea areas as Bridled Terns (Onychoprion anaethetus) over the Gulf Stream (4). Occasionally attends small fishing boats. Off eastern North America, favors waters over the shelf slope, and is usually observed in flocks, which sometimes number hundreds of birds (4). In the Caribbean, a recent modeling study based on the species’ nesting grounds suggested that foraging sites for males are more densely aggregated, whereas those of females are less densely clustered, but, for both, a correlation between the proximity of nesting locations and likely frontal regions is clear, indicating that nesting locations are probably associated with predictable thermal fronts (22).

Food Capture and Consumption

Prey caught by pursuit-diving and pursuit-plunging, pattering, and surface-seizing (23). Dives can last several seconds.

Diet

Off North Carolina, regularly takes Sargassum-associated prey (59%), mainly fish (including Exocoetidae, Priacanthus sp., Heteropriacanthus cruentatus, Caranx sp., C. hippos, Decapterus sp., Trachurus lathami, Stromateidae, Balistidae, Aluterus sp., Monacanthus ciliatus, Stephanolepis hispidus, Sphoeroides sp. and, especially, Monacanthus sp.) (24).

Vocalizations

A rhythmic, wheezing, fairly fast-paced, bleating call comprising 4–5 syllables, which is typically repeated several times in rapid succession, transcribed h'whieh-whieh huhr, h'whieh-whieh-huhr..., or wh'whieh-whieh h'hr (4). Described as sounding like a “squeaky, strangled” Manx Shearwater (Puffinus puffinus), with sexual dimorphism similar to in other shearwaters, i.e., female calls being lower in frequency and harsher (more gravelly) than those of males (4). Most populations are strictly nocturnal at colonies, and therefore only call by night. Generally silent at sea.

Phenology

Season mainly in January/March–May/July (25, 26, 1), occasionally as early as December (27), while recently discovered populations off Brazil (on Fernando do Noronha, Itataia Islands, believed to involve P. lherminieri) apparently lay eggs August–September, have downy chicks in September–October, and full-grown chicks in October, but there seems to be great inter-annual variation in breeding phenology (2, 28).

Nest Site

Colonial, often at low densities and in comparatively small numbers; nests in rock crevices or self-excavated burrows (60–200 cm long).

Eggs

Single white egg, mean size 49.3–55.0 × 33.2–38.4 mm, mass 30–40 g (off Brazil) (2, 3, 28).

Incubation

Incubation 44–60 days, with stints of 2–10 (mean 3.5) days (23).

Young Birds

Chicks have grayish down above, white below.

Parental Care

Brooding

Brooded for 3–7 days (23).

Fledgling Stage

Fledging 62–100 (mean 75) days (23).

Measures of Breeding Activity

Very limited data on breeding success.

Life Span and Survivorship

Sexual maturity at c. 8 years (23).

Conservation Status

Global conservation status not evaluated according to IUCN criteria. However, the species is considered Critically Endangered in Brazil, where known population is tiny, see below (29). Widespread and locally abundant, with total population estimated to number 7,400–20,500 pairs in the West Indies (30), versus an earlier estimate of just 3,000–5,000 pairs (31). On the plus side, small colonies have only recently been discovered off northern Cuba (32) and in St Lucia (33), but negatively the species has been extirpated from both Bermuda (14, 15) and Antigua at various periods in the distant past (23). Other small populations (ascribed to this species) have also been recently discovered (and perhaps represent recent colonizing events) on the Fernando de Noronha  archipelago (where known to nest on at least two small islets off the main island), and the Itatiaia Islands, both off eastern Brazil (2, 28), but it has been suggested that it could occur on other islands in this region, especially off the states of Bahia, Espírito Santo and northern Rio de Janeiro, many of which are poorly surveyed for birds (29). Most colonies are not large, but in 1991 c. 500 pairs were estimated to be nesting on Long Cay, in the Exumas, eastern Bahamas (25) and some 1,650–2,800 pairs nest on Elbow Cay, also in the Bahamas, which is believed to be the largest single subpopulation at present (34). Subfossil remains attributable to the species have also been found on Ascension Island, in the central Atlantic (16), and fossils have also been reported from several small islands in the Bahamas without modern-day indications of breeding (35, 36, 37). The not always recognized race loyemilleri has been suggested to be close to extinction (23). Intense human exploitation in past, which continues in places. On some islands in the Lesser Antilles, rats (Rattus rattus) are comparatively numerous, although it is unknown if they are reducing local populations of the species via predation of eggs and nestlings, while goats are ubiquitous on islands, such as Saba, and may crush shearwater burrows (27). Its sedentary habits render distinct small populations more vulnerable to human exploitation.

Recommended Citation

Kirwan, G. M., C. Carboneras, and F. Jutglar (2020). Audubon's Shearwater (Puffinus lherminieri), version 1.0. In Birds of the World (S. M. Billerman, B. K. Keeney, P. G. Rodewald, and T. S. Schulenberg, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.audshe.01