White-faced Storm-petrel (Pelagodroma marina)

Taxonomy

According to HANZAB, the scientific name for the genus (Pelagodroma) is a tautological compound of the Greek meaning something like 'the marine runner of the high seas' - an apt description of this highly enigmatic storm-petrel. Also goes under a variety of English names (some used for other species) including, Frigate Petrel, White-breasted Storm-Petrel, Storm-petrel and most confusingly, Mother Carey's Chicken!


Figure 1. White-faced Storm-petrel photographed on 29 August 1999 in cooler water just northwest of the Gulf Stream off Oregon Inlet, North Carolina, USA. The bird was spotted by the sharp eyes of Brian Patteson as it fed along the edge of a patch of sargassum weed. Notice the distinctive white forehead and supercilium, contrasting with the dark crown and neat black bar across the eye. This and the images below are still captures from a digital video. Although the video captured the bounding flight style beautifully, the shutter speed was not fast enough for good still images hence the very blurred wings. Copyright of Angus Wilson©

At least five subspecies are recognized:
P. m. marina - Tristan da Cunha and South Atlantic
P. m. dulciae - w. and s. Australia, Indian Ocean
P. m. maoriana - New Zealand and s. and e. Pacific
P. m. hypoleuca - Salvage Islands
P. m. eadesi - Cape Verde Islands
(P. m. albiclunis - Kermadec Islands. -providence uncertain)
 

Identification

Readily identified by combination of brown upperparts contrasting with black primary coverts, remiges and tail; mostly white underparts and distintive facial pattern. Has extremely long black legs and toes, with paler (creamy) webs between the toes. Tarsus measurements are between 40 and 43 mm depending slightly on sex and race. On average females have longer wings and tails. According to HANZAB, juveniles are not separable from adults in the field. The relatively long tail is slightly forked in some subspecies (e.g. maoriana).


Figure 2. White-faced Storm-petrel photographed on 29 August 1999 in cooler water just northwest of the Gulf Stream off Oregon Inlet, North Carolina, USA. Banking away, revealing the white underwing coverts edged by the dark brown primaries and secondaries. Copyright of Angus Wilson©

Distinctive flight involves erratic weaving and banking actions. The wings a held stiffly out from the body, and slightly bowed. Audubon Shearwater may also hold its wings in this manner, potentially causing confusion. In direct flight, a quick series of jerky wingbeats are followed by a long glide on straight wings. The wings are almost always held fully extended, even in power flight. In direct flight, the feet and tarsi project well beyond the tail. In the southern oceans, might be confused with with prions. In the North or South Atlantic might be confused with partly albinistic Wilson's Storm-petrels. Confusion with basic-plumage phalaropes is an outside possiblity, however the flight style is totally different.

In the Pacific, White-faced Storm-petrels feed on copepods and euphausiid shrimp. Stomach analysis of specimens collected in the North Atlantic off North Carolina found evidence of small fish, egg masses, crustacean larvae and marine water-striders (Watson et al., 1986).


Figure 3. White-faced Storm-petrel photographed on 29 August 1999 in cooler water just northwest of the Gulf Stream off Oregon Inlet, North Carolina, USA. Side view showing distinctive facial pattern and white flanks and brownish coloration of the mantle extending as a half-collar onto the sides of the upper breast. Bourne (1953), laid out criteria for separation of the Cape Verde Island subspecies P. m. eadesi and the Salvage Islands form P. m. hypoleuca. In Cape Verde birds, the white of the breast and throat is normally continuous with the broad white supercilium. The Salvage Island subspecies (P. m. hypoleuca) has a more diffuse facial mask which typically isolates the supercilium. Cape Verde Island are supposed to be longer legged, with a greater extension beyond the tail in direct flight. Photograph copyright of Angus Wilson©
 

Where and When

Breeds in a number of temperate and subtropical regions of the Atlantic, Indian Ocean and south Pacific, especially around southern Australia and New Zealand. Total world population probably exceeds several million birds. Well over 1 million breed in New Zealand. Colonies are vulnerable to damage by grazing animals (e.g. goats and cows) and human tourists which tramble the burrows and destroy protective vegation, increased presence of gulls (e.g. breeding Silver Gulls on the Five Island Group, New South Wales) and rodents which eat adults as well as young. Generally solitary, but may form larger flocks (e.g. 100s) nearer breeding islands. Major die-offs due to entanglement of the legs by the filamentous larvae of trematode worms (Distomum filiferum) has also been documented. For example, in 1970 some 200,000 were found dead on Chatham Island, New Zealand.

Some 0.5 million birds estimated in the Salvage Island population. Most North American records have come from deep-water canyons off the eastern seaboard from the Carolinas to New England (reviewed in Watson et al., 1986; Mlodinow and O'Brien, 1996). Detailed review of specimens and photographs suggests that the vast majority of North American records refer to P. m. eadesi - the taxa breeding on the Cape Verde Islands. The pattern of records suggests that both adults and first year birds migrate northwestwards across the North Atlantic to spend the late summer and early fall on the Continental Shelf and Slope of the eastern United States. The oceanic conditions (salinity and temperature) resemble the non-breeding grounds in the Indian Ocean used by Australian breeders. In addition, there are a small number of records from land (e.g. Connecticut and North Carolina), most associated with Hurricanes.

In the south Pacific, adults begin body molt before leaving the breeding grounds and start to molt the inner primaries shortly after arrival on the wintering grounds. Tail feathers are molted after the primary molt is complete.
 

Photographs on the web

A number of pictures from the western north Atlantic are available, presumably referring to the Cape Verde Island race, P. m. eadesi:

(1) Nice view of uppersurface as it takes a bound off the water using its very long legs. Photograph by Brian Patteson and posted on his excellent pelagic tour site.
(2) Classic black-and-white image again taken by Brian Patteson showing details of the underparts, head and legs.

(3) Side view in black-and-white. Photograph by Alan Brady, taken in 1993 and posted on the Focus on Nature Tours (FONT) web site.
(4) Another side view by Alan Brady, showing the increadibly long legs and feet.
(5) Here is a color photo, possibly of the same bird, carrying a tasty lump of shark's liver. Photograph by Laurie Larson and again posted on the FONT web site.

Tony Palliser has posted a couple of images from the southeastern Australia, presumably representing the subspecies P. m. dulciae:

(6) Pinsharp study of the upper surface and head. Notice the difference in facial pattern and bill length compared to the north Atlantic birds. Photograph by Tony Palliser and taken off Sydney, NSW in September.
(7) Another uppersurface shot, possibly of the same bird as above?


Figure 4. White-faced Storm-petrel photographed on 29 August 1999 in cooler water just northwest of the Gulf Stream off Oregon Inlet, North Carolina, USA. Another side view showing more detail of the long narrow bill, strongly downcurved at the tip. The raised nostril is also quite prominent as is the steep forehead. Copyright of Angus Wilson©
 

Literature

Bourne, W.R.P. (1953) On the races of the Frigate Petrel (Pelagodroma marina, Latham) with a new race from the Cape Verde Islands. Bull. Brit. Ornith. Club 73: p79-82.

Buckley, P.A. and Wurster, C.F. (1970) White-faced Storm-Petrels Pelagodroma marina, in the North Atlantic. Bull. Brit. Ornith. Club 90: p35-38.

Marchant and P. J. Higgins (1990) Handbook of Australian, New Zealand and Antarctic Birds. Vol 1 (Ratites to Ducks).

Mlodinow, S. G. and O'Brien, M. (1996) America's 100 Most Wanted Birds: Finding the lower 48's rarest species. Falcon Press, Helena and Billings, Montana.

Morzer Bruyns, W.F.J. and Voous, K.H. (1964) White-faced Storm-petrels (Pelagodroma marina) in the Indean Ocean. Ardea 52: p223-224.

Roselaar, C.S. (1975) A record of the Frigate Petrel Pelagodroma marina off the Altantic coast of North America. Ardea 63: p152-153.

Watson, G.E., Lee, D.S., and Backus, E.S. (1986) Status and subspecific identity of White-faced Strom-petrels in the western North Atlantic Ocean. American Birds 40(3): p401-408.
 


Figure 5. White-faced Storm-petrel photographed on 29 August 1999 in cooler water just northwest of the Gulf Stream off Oregon Inlet, North Carolina, USA. Banking away, showing details of the upper surface of the wings, including the warm brown mantle and scapulars. The upper tail coverts are light gray with paler bases. The tail feathers are dark brown. Pale tips to the greater upperwing coverts great a narrow pale bar contrasting with the brown median and lesser coverts as well as darker primaries and secondaries. Copyright of Angus Wilson©



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