SHEARWATERS & PETRELS Procellariidae There is just something about procellarids, the shearwaters and petrels. Perhaps it is their gliding flight  over the waves, covering huge distances without apparent effort. Perhaps it is the fact that we must venture away from our land habitat into the open ocean to observe them, and therefore rarely see them well from a constantly moving boat. Perhaps it is awe for their incredible transequatorial migrations, knowing that a bird seen in the Gulf of Alaska was nesting in the Southern Hemisphere just a month or so before. The Buller's Shearwater (left or above) is an example; it nests in New Zealand and then undertakes a great clockwise migration around the north Pacific, reaching Monterey Bay (as in this photo) every August-September (that's a Sooty Shearwater in the background).


Shearwaters and petrels have a remarkable following around the world; they are among the most sought after of birds. Just about 30% of procellarids are shearwaters (genera Puffinus & Calonectris). Aside from a handful of prions, fulmars and giant-petrels, the majority are petrels in 8 genera. Some 28 species are Pterodroma petrels, the really far-out procellarids ranging thousands of miles offshore and at home in the wildest sea and wind conditions. A Pterodroma arcing over the horizon is the epitome of the untamed ocean realm. They are just the classic seabird. A fine example from the Indian Ocean is Barau's Petrel (right). Almost nothing is known about its life at sea. It breeds only on the Mascarene Islands; this adult is heading ashore on Réunion Island late in the afternoon.

Virtually all procellarids breed on offshore islands, many of them using burrows or caves. Because they nest on the ground they are especially susceptible to ground predators. Dogs, cats, rats, weasels and the like are death of breeding adults and their young. Because there are so few predator-free islands, procellarids have declined in many places globally. Most nesting islets are barren and foreboding places. Because we encounter petrels almost always in the open ocean -- out of sight of land -- is always dramatic to see a petrel flying near a breeding island. I very much like these two following shots:
a Barau's Petrel heading up the St. Etienne River valley on Réunion (left) and Greg Lasley's dramatic shot of a Southern Giant-Petrel with its South Georgia island home dramatically in the background (right).

Although part of what shearwaters and petrels are about is lonely isolation against the endless sea, the group has its moments of true wildlife spectacle. These can include the hundreds of thousands of Sooty Shearwaters (below, top photo) that circle the shores of Monterey Bay, California, in the northern summer (here in a feeding frenzy with gulls and pelicans); or the array of species on Monterey Bay in the northern autumn [below, center; among Western Gulls Larus occidentalis are Buller's Shearwater, Pink-footed Shearwater (pale-based bills) and Sooty Shearwater]; or flights of Antarctic Prions (below, bottom) at high latitudes in the South Atlantic Ocean (in a photo by Greg W. Lasley).

Yet another aspect of procellarids that makes them fascinating is the fact that a fair number are difficult to identify at sea, and there has been a progression of knowledge in recent years as one after another seemingly intractable problem is worked out. There are six species of prions -- plus the tiny Blue Petrel Halobaena caerulea -- that pose challenges for those on subantarctic cruises. Some of these conundrums have yet to be resolved. But great progress has been made in separating the 7 tiny Pterodroma petrels in the tropical Pacific collectively known as the 'Cookilaria' petrels. I'm proud to have a been a part of pushing forward the "frontiers of bird identification" concerning them.


During four months at sea as a seabird researcher about the U.S. vessel MacArthur on a NOAA tuna-porpoise research cruise in fall 1989, I gained firsthand experience with five of the taxa and took copious notes and photos. On my return I received a Chapman grant to travel to the American Museum of Natural History in New York to examine their impression collection, take measurements (above; measuring the bill of a Cook's Petrel specimen), and do comparative studies. At that time there was no known field method to distinguish Cook's (a species breeding in New Zealand but ranging to California and Chile) from DeFilippi's Petrel (a species breeding on the Juan Fernandez Is. off Chile). In the basement of the American Museum I looked at rows of specimens of each as they lay on their backs in the museum drawers. Then I turned them all over and WOW! I made a discovery that was as exciting to me as anything I'd ever seen in the field. I could conclusively separate any age, any sex, any state of molt -- by the pattern at the tip of the tail. In P. cookii there was always a darker tip to the pale gray central rectrices. In P. defilippiana the pale gray color continued right to the tip. A true breakthrough, and one overlooked by Murphy (1936), by Harrison (1983, 1987), by everyone! The detail has since been field tested with great success (out of hundreds of each seen in the field, only one claimed DeFilippi's has not been immediately separable on this point; see Howell et al. 1987). Steve Bailey and I published this new character -- and many others -- in our major two-part paper on the identification and distribution of "Cookilaria" (Roberson & Bailey 1991) which includes the first accurate group painting by Keith Hansen (above right; top row are Stejneger's P. longirostris, Cook's, and Pycroft's P. pycrofti; bottom are White-winged P. leucoptera, DeFilippi's, and Black-winged P. nigripennis). [The 7th 'Cookilaria' is Collared Petrel P. brevipes, assuming one considers it a good species. It shows great variation on the underparts from all-white (like White-winged) to almost all dark. It otherwise acts like White-winged and the two have identical shapes and flight behaviors to my eye. I suspect that P. leucoptera is simply a polymorphic species.]

Our research made identifying photos much easier and we were able to re-evaluate and re-identify several photos in Harrison (1987). [Plate 129 is DeFilippi's Petrel not a Cook's, plate 135 is a Cook's not a Pycroft's]. The 'Cookilaria' shown at left is a DeFilippi's Petrel off Chile (photographed by Robert L. Pitman). Note not only the lack of a dark tip to the tail but the big gray wedge extending downward at the shoulder and the very crisp facial pattern. It is also much bigger-billed and shorter-winged that Cook's. Ironically, it and Pycroft's are the only 'Cookilaria' with which I lack field experience. One of my most important contributions to field identification was with a bird I've never seen!

Pterodroma petrels are also exciting because we are just learning their distributions at sea. In the Atlantic Ocean, observers have just recently discovered that Fea's Petrel P. feae, Trindade Petrel P. arminjoniana (the Atlantic Ocean version of Herald Petrel P. heraldica), and even the endangered Bermuda Petrel P. cahow may be regular in summer. Their identification has just recently been understood (Tove 1997, Wingate et al. 1998). In the North Pacific we have learned in the past 25 years that Cook's Petrel and Murphy's Petrel P. ultima are apparently regular well offshore, that both Mottled P. inexpectata and Stejneger's P. longirostris are likely regular in migration way out there (see McCaskie & Roberson 1992 for details of the first record of the latter species), and Great-winged Petrel P. macroptera visits on occasion.


Indeed, I found during a research cruise in April 1991 well offshore between Pt. Sur to Pt. Año Nuevo, California, in very rough weather, that Murphy's Petrel (left and above) was the commonest bird out there beyond 50 miles offshore! These two shots are from that cruise. Until very recently this was almost a complete mystery bird; "little known" in the words of Harrison (1983.) Both its identification (Bailey et al. 1989) and aspects of its biology (Zimmer 1992) have recently been worked out.

I could go on and on about the distribution and identification of petrels. So much of the literature has errors that have been recopied time and again that both the Handbook of the Birds of the World account of the Procellariidae (Carboneras 1992) and a recent photo i.d. book (Enticott & Tipling 1998) have conspicuous mistakes; among other points, they overlooked the fabulous mapping of seabird distribution by Pitman (1986). But perhaps it is more fun to focus on positive aspects. The influence of water temperature and salinity conditions on distribution is important (some aspects for the northeast Pacific have been summarized by Ainley 1976 and Briggs et al. 1987). Vagrancy among procellarids is indeed impressive, and was recognized a few decades ago by Bourne (1967). A substantial amount of wandering is influenced by conditions on a global scale. El Niño-Southern Ocellation conditions greatly impact bird distribution when they occur, and the "great" El Niños (like 1982-1983 and 1997-1998) engender distant incursions of warm water species, sometimes for years afterwards until a more "typical" balance is restored. One such example might be California's third Wedge-tailed Shearwater which was in Monterey Bay for several weeks in October 1998:

See Stallcup et al. 1988 for details of the first California record and some i.d. tips. I also co-authored a paper on the second state record of Streaked Shearwater Calonectris leucomelas (Roberson et al. 1987).

Taxonomic issues in the Procellariidae are legion and provide much entertainment. Carboneras (1992) begins his discussion of this family by saying: "The taxonomy of the Procellariidae is extraordinarily complex, and it is consequently subject to frequent revisions, and more than its fair share of polemic." Roberson & Bailey (1991) discussed the tangled nomenclature of the small Pterodromas that includes a profusion of scientific names that confused authors up to today. Just one of numerous other examples are the small black-and-white shearwaters in the genus Puffinus. Murphy (1952) lumped many around the world as "Manx Shearwater P. puffinus." This was well wide of the mark and the modern trend is to separate isolated island populations in different oceans as distinct species. But even then there remains debate: should Newell's Shearwater P. newelli in Hawaii be lumped with Townsend's Shearwater P. auricularis of the Revillagigedos Is., Mexico? Jehl (1982) argued they should be lumped (mostly on vocalizations) but most recent authors do not agree, including those who have published on identification topics as I have done (Roberson 1996; see also Howell et al. 1994). And what of the populations in the Mediterranean? Yésou et al. (1990) had some answers. Then there is the additional problem of claims of new species of small black-and-white shearwaters (Shirihai et al. 1995; see also Enticott & Tipling 1998) whose breeding grounds are unknown. These claims have been subject to criticism recently but it does seem likely that the Audubon's Shearwater group has been overlumped.

These taxonomic issues sometimes overshadow the truly impressive range expansion in the last half-century by the Manx Shearwater of the North Atlantic. Once restricted as a breeding species to islands off nw. Europe (Scotland, etc.) it first colonized n.e. North America and then began an explosion of vagrancy that took birds all the way to New Zealand and Australia (see Kinsky & Fowler 1973 for details of a bird banded in Britain being picked up in Australia). The first vagrants to the n.e. Pacific were in the late 1970s; by the 1990s Manx Shearwater had become a regular migrant and winterer in small numbers in Monterey Bay. They must be nesting somewhere around the Gulf of Alaska now as we see young birds in the fall (many more details are in Roberson 1996). This is as impressive a range expansion as any species on earth!

The plumage of shearwaters and petrels is often dominated by patterns of black, white, or gray. These can be very dramatic at sea against the deep blue or green ocean, and providing an impression that can be as memorable as the most colorful toucan or parrot. Here are three of my favorites in terms of dramatic pattern: the stylish Dark-rumped Petrel (below left) is sleek and long-tailed (there are populations in the Galapagos where this shot was taken, and in Hawaii, that could represent separate species); the pure white Snow Petrel of the highest southern latitudes (below center in a shot by Greg W. Lasley; I've not seen this species but those who have speak of it with affection); and the bold pied patterning of the Cape Petrel (below right), a widespread southern hemisphere procellarid that ranges to the Equator in the Peru Current.

I haven't even touched on breeding biology or foraging ecology. Many details are packed into Warham (1995) and summarized by Carboneras (1992). But I did want to mention the amazing interaction between some petrels and cetaceans. Juan Fernandez Petrels and Wedge-tailed Shearwaters are among the foraging seabirds regularly found around tuna-porpoise assemblages in the eastern tropical Pacific (see Au & Pitman 1986). My four months at sea in 1989 included studying these associations. Even more specific and dramatic is evidence that the New Zealand breeding Parkinson's Petrel Procellaria parkinsoni consistently forages with pods of Melon-headed Whale Peponocephala electra and False Killer Whale Pseudorca crassidens in the tropical Pacific. Nearly two-thirds of all observations on multiple research cruises were in direct association with these two species (Pitman & Ballance 1992). On my cruise in fall 1989, I noticed that the few Phoenix Petrels seen were often associated with large cetaceans. Below is my shot of a Phoenix Petrel in the wake of an Orca (Killer Whale) way offshore in the eastern tropical Pacific. Yes, there is still much to be learned about procellarids....

Photos: The Buller's ShearwaterPuffinus bulleri was photographed on Monterey Bay on . Both shots of Barau's PetrelPterodroma baraui were at the St. Etienne R. mouth, Réunion I., Indian Ocean, on 9 Dec 1992. The Southern Giant-Petrel Macronectes giganteus was photographed by Greg W. Lasley off South Georgia I., South Atlantic Ocean, on 26 Jan 1999. The swarms of Sooty Shearwater  Puffinus griseus were just off the Salinas R. mouth, Monterey Co., California, on . The mixed flock of Buller's, Sooty, and Pink-footed ShearwaterPuffinus creatopus were Monterey Bay on 29 Sep 1989. The flock of Antarctic PrionPachyptila desolata were shot by Greg W. Lasley off South Georgia Island, South Atlantic, Ocean, on 26 Jan 1999. Although the Cook's Petrel Pterodroma cookii specimen illustrates the discussion of the AMNH research that led to the paper with Keith Hansen's fine painting, the actual specimen shown here is at California Academy of Science, San Francisco, and it represents the first specimen record for California (found ashore in Santa Cruz 17 Nov 1983; #CAS71447). Robert L. Pitman photographed the DeFilippi's Petrel Pterodroma defilippiana off Chile in June 1986. Both shots of Murphy's Petrel Pterodroma ultima were on 8 Apr 1991 about 100 nmi WSW of Pt. Año Nuevo, San Mateo Co., California. The dark-morph Wedge-tailed Shearwater Puffinus pacificus was in Monterey Bay, Monterey Co., California, on 11 Oct 1998. The Dark-rumped Petrel Pterodroma phaeopygia was between Isabella & Santa Cruz Is., Galapagos, on 23 Sep 1989. Greg W. Lasley photographed the Snow Petrel Pagodroma nivea in the Scotia Sea near South Georgia I. on 2 Feb 2000. The Cape Petrel Daption capense was off the Paracas Peninsula, Peru, in July 1987. The interaction between the Phoenix Petrel Pterodroma alba and the Orca Orcinus orca was at 7°30'N, 144°30'W, on 5 Sep 1989.  All photos © 2001 Don Roberson except those attributed to Greg W. Lasley and Robert L. Pitman who hold those copyrights (used with permission), all rights reserved.

Bibliographic essay

Family Book: II rating (out of 5 possible; see below)

There are many seabird books but apparently none that can strictly be called a family book on the Shearwaters and Petrels. A very fine introduction to the family, with a selection of nice photos, is in Carboneras (1992). There is much to glean from the beautifully written prose in Murphy (1936) but it is limited to the waters off South America. Warham (1995) summarizes behavior and physiology but does not do so species-by-species; it is not a "family book." Photographs of all species are in Harrison (1987) and in Enticott & Tipling (1998), and art and text in Harrison's earlier work (Harrison 1983). Harrison's efforts were monumental for their time but one must now be very careful in using the text (esp. of the earlier book) which is riddled with errors.

The sea-birder cannot rely on any standard text for shearwaters and petrels. Information about taxonomy, distribution, and identification is being learned and revised so quickly that books are often out-of-date by the time they are published (sadly, this means the species summaries in Carboneras 1992, Enticott & Tipling 1998, and others are misleading). A good local text is often best. In the Monterey Bay area especially useful books on seabirds (including all the shearwaters) are by Stallcup (1976, 1990). But for the difficult groups, see some of the literature listed below. For North Atlantic Petrodromas, Tove (1997) and Wingate et al. (1998) are a must. For the 'Cookileria' Pterodromas of the Pacific, Roberson & Bailey (1991) is essential. For the dark Pterodromas of the Pacific, Bailey et al. (1989) is key. For good tips on separating the Tahiti/Phoenix petrels and on other tropical Pacific problems, see Spear et al. (1992). On the small black-and-white shearwaters of the eastern Pacific, one must read Howell et al. (1994) or Roberson (1996). I am not as well-versed in the literature of Australasian and subantarctic problems but, as in the northern hemisphere, I suspect the real gold lies in articles and papers and not in books published to date.

Other literature cited:
Ainley, D. G. 1976. The occurrence of seabirds in the coastal region of California. W. Birds  7:33- 68.

Au, D. W. K., and R. L. Pitman. 1986. Seabird interactions with dolphins and tuna in the eastern tropical Pacific. Condor 88: 304-317.

Bailey, S. F., P. Pyle, and L. B. Spear. 1989. Dark Pterodroma petrels in the North Pacific:   identification, status, and North American occurrence. Am. Birds 43: 400-415.

Briggs, K. T., W. B. Tyler, D. B. Lewis, and D. R. Carlson. 1987. Bird Communities at Sea off California: 1975 to 1983. Studies in Avian Biology 11.

Bourne, W. R. P. 1967. Long-distance vagrancy in the petrels. Ibis 109:141-167.

Carboneras, C. 1992. Family Procellariidae (Petrels and Shearwaters) in Handbook of the Birds of the World (J. del Hoyo, A. Elliott, & J. Sargatal, eds). Vol. 1. Lynx Edicions, Barcelona.

Enticott, J. and D. Tipling. 1998. Photographic Handbook of the Seabirds of the World. Rev. ed. New Holland, London.

Harrison, P. 1983. Seabirds: an Identification Guide. Boston: Houghton Mifflin.

Harrison, P. 1987. Seabirds of the World: a Photographic Guide. Bromley, England: Christopher Helm. [Published in the U.S. as Field Guide to the Seabirds of the World,   Lexington, MA.: Stephen Greene Press]

Howell, S. N. G., L. B. Spear, and P. Pyle. 1994. Identification of Manx-type Shearwaters in the eastern Pacific. West. Birds 25: 169-177.

Howell, S. N. G., S. Webb, and L. B. Spear. 1996. Identification at sea of Cook’s, De Filippi’s, and  Pycroft’s petrels. W. Birds 27: 57-64.

Jehl, J. R., Jr. 1982. The biology and taxonomy of Townsend's Shearwater. Le Gerfaut 72: 121-  135.

Kinsky, F. C., and J. A. Fowler. 1973. British-ringed Manx Shearwater in Australia. British Birds   55: 86-87.

McCaskie, G., and D. Roberson. 1992. First record of the Stejneger's Petrel in California. W.   Birds 23: 145-152.

Murphy, R. C. 1936. Oceanic Birds of South America. 2 vols. Amer. Mus. Nat. Hist., New York.

Murphy, R. C. 1952. The Manx Shearwater as a species of world-wide distribution. Amer. Mus. Novitates 1586: 1-21.

Pitman, R. L. 1986. Atlas of Seabird Distribution and Relative Abundance in the Eastern Tropical Pacific. La Jolla, California: NOAA, NMFS, Southwest Fisheries Center    Administrative Report LJ-86-02C.

Pitman, R. L., and L. T. Ballance. 1992. Parkinson's Petrel distribution and foraging ecology in the eastern Pacific: aspects of an exclusive feeding relationship with dolphins. Condor 94: 825-835.

Roberson, D. 1996. Identifying Manx Shearwaters in the northeastern Pacific. Birding 28: 18-  33.

Roberson, D. and Bailey, S. F. 1991. Cookilaria petrels in the eastern Pacific Ocean: identification and distribution. Am. Birds 45: 399-403 (Part I); 45: 1067-1081   (Part 2).

Roberson, D., J. Morlan, and A. Small. 1977. A Streaked Shearwater in California. Am. Birds   31: 1097-1098.

Shirihai, H., I. Sinclair, and P. R. Colstron. 1995. A new species of Puffinus shearwater from the western Indian Ocean. Bull. Brit. Ornith. Club 115: 75-87.

Spear, L. G., S. N. G. Howell, and D. G. Ainley. 1992. Notes on the at-sea identification of some Pacific gadfly petrels (genus Pterodroma). Colonial Waterbirds 15: 202-218.

Stallcup, R. 1976. Pelagic birds of Monterey Bay, California. Western Birds 7: 113-136.

Stallcup, R. 1990. Ocean Birds of the Nearshore Pacific. Pt. Reyes Bird Observatory, Stinson Beach, CA.

Stallcup, R., J. Morlan, and D. Roberson. 1988. First record of the Wedge-tailed Shearwater in California. W. Birds 19: 61-68.

Tove, M. H. 1997. Fea's Petrel in North America. Birding 29: 206-214 (Part 1), 29: 309-315 (Part 2).

Warham, J. 1995. The Behaviour, Population Biology and Physiology of the Petrels. Academic Press, London.

Wingate, D. B., T. Hass, E. S. Brinkley, and J. B. Patteson. 1998. Identification of Bermuda Petrel: new light on an endangered species. Birding 30: 18-36.

Yésou, P., A. M. Paterson, E. J. Mackrill, and W. R. P. Bourne. 1990. Plumage variation and identification of the 'Yelkouan Shearwater.' British Birds 83: 299-319.

Zimmer, K. J. 1992. Murphy's Petrels on Ducie Atoll: another piece of the puzzle. American Birds 46: 1100-1105.

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