Sooty shearwater

The sooty shearwater (Ardenna grisea), or tītī, or muttonbird, is a medium-large shearwater in the seabird family Procellariidae. In New Zealand, it is also known by its Māori name tītī, and as muttonbird, like its relatives the wedge-tailed shearwater (A. pacificus) and the Australian short-tailed shearwater (A. tenuirostris).

Sooty shearwater
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Class: Aves
Order: Procellariiformes
Family: Procellariidae
Genus: Ardenna
Species:
A. grisea
Binomial name
Ardenna grisea
(Gmelin, JF, 1789)
Range of the Sooty shearwater in dark blue and breeding sites in yellow

Taxonomy

The sooty shearwater was formally described in 1789 by the German naturalist Johann Friedrich Gmelin under the binomial name Procellaria grisea.[2] The shearwater had been briefly described in 1777 by James Cook in the account of his second voyage to the Pacific,[3] and in 1785 the English ornithologist John Latham had described a museum specimen.[4] The sooty shearwater is now placed in the genus Ardenna, that was introduced in 1853 by Ludwig Reichenbach.[5][6] The genus name Ardenna was used to refer to a seabird by Italian naturalist Ulisse Aldrovandi in 1603, and the specific epithet grisea is medieval Latin for "gray".[7] The species is considered to be monotypic; no subspecies are recognized.[6]

It appears to be particularly closely related to the great shearwater (A. gravis) and the short-tailed shearwater, all blunt-tailed, black-billed species, but its precise relationships are obscure.[8][9][10] In any case, these three species are among the larger species of shearwaters that have been moved into a separate genus Ardenna based on a phylogenetic analysis of mitochondrial DNA.[11][12][13]

Description
Up close, the chocolate-coloured plumage can be appreciated.

Sooty shearwaters are 40–51 cm (16–20 in) in length with a 94–110 cm (37–43 in) wingspan.[14] It has the typical "shearing" flight of the genus, dipping from side to side on stiff wings with few wing beats, the wingtips almost touching the water. Its flight is powerful and direct, with wings held stiff and straight, giving the impression of a very small albatross. This shearwater is identifiable by its dark plumage, which is responsible for its name. In poor viewing conditions, it looks all black, but in good light, it shows as dark chocolate-brown with a silvery strip along the center of the underwing.

Usually loud, sooty shearwaters coo and croak while on the breeding grounds.

In the Atlantic, it is the only such bird, whereas in the Pacific part of its range, other all-dark large shearwaters are found. The short-tailed shearwater in particular is almost impossible to tell apart from the present species at a distance.[15]

Distribution and habitat
Upper body of a bird swimming off the shore of California

Sooty shearwaters breed on small islands in the south Pacific and south Atlantic Oceans, mainly around New Zealand, the Falkland Islands, Tierra del Fuego, and in the Auckland Islands and Phillip Island off Norfolk Island. They start breeding in October, and incubate their young for about 54 days. Once the chick hatches, the parents raise their chick for 86 to 109 days.[14]

They are spectacular long-distance migrants, following a circular route,[16] traveling north up the western side of the Pacific and Atlantic Oceans at the end of the nesting season in March–May, reaching subarctic waters in June–July, where they cross from west to east, then return south down the eastern side of the oceans in September–October, reaching to the breeding colonies in November. They do not migrate as a flock, but rather as individuals, associating only opportunistically; in June 1906, for example, two were shot near Guadalupe Island off Baja California, Mexico, several weeks before the bulk of the population would pass by.[17] Likewise, the identity of numerous large, dark shearwaters observed in October 2004 off Kwajalein in the Marshall Islands remain enigmatic; they might have been either sooty or short-tailed shearwaters, but neither species is generally held to pass through this region at that time.[15]

In the Atlantic Ocean, they cover distances in excess of 14,000 km (8,700 mi) from their breeding colony on the Falkland Islands (52°S 60°W) north to 60 to 70°N in the North Atlantic Ocean off north Norway; distances covered in the Pacific are similar or larger; although the Pacific Ocean colonies are not quite so far south, at 35 to 50°S off New Zealand, and moving north to the Aleutian Islands, the longitudinal width of the ocean makes longer migrations necessary. Recent tagging experiments have shown that birds breeding in New Zealand may travel 74,000 km in a year, reaching Japan, Alaska, and California, averaging more than 500 km per day.[18]

In Great Britain, they move south in late August and September; with strong north and north-west winds, they may occasionally become "trapped" in the shallow, largely enclosed North Sea, and heavy passages may be seen flying back north up the British east coast as they retrace their path back to the Atlantic over northern Scotland.

Ecology and status
A small portion of a huge flock off the shore of California, United States in September

The sooty shearwater feeds on fish and squid. They can dive up to 68 m deep for food,[18] but more commonly take surface food, in particular often following whales to catch fish disturbed by them. They also follow fishing boats to take fish scraps thrown overboard. Isotopic analyses revealed significant niche overlap between sooty shearwaters and great shearwaters.[19]

They breed in huge colonies and the female lays one white egg. These shearwaters nest in burrows lined with plant material, which are visited only at night to avoid predation by large gulls. The architecture of sooty shearwater burrows can vary within and between breeding colonies, and is influenced by competition for breeding space and habitat type, with soil under dense tussac grass being easier to excavate than other substrates.[20]

In New Zealand, about 250,000 muttonbirds are harvested for oils and food each year by the indigenous Māori population.[14] Young birds just about to fledge are collected from the burrows, plucked, and often preserved in salt. in 2022, climate change was thought to be impacting this cultural harvest by Ngāi Tahu.[21]

Its numbers have been declining in recent decades, and it is presently classified as near threatened by the IUCN.[1] In 2009, the harvest reported record-low catches, on average a trapping cage yielded nearly 500 birds; in 2009, the number was estimated to be closer to 40 per cage.

Inspiration for Hitchcock's The Birds

On August 18, 1961, the Santa Cruz Sentinel reported that thousands of crazed sooty shearwaters[22] were sighted on the shores of North Monterey Bay in California, regurgitating anchovies, flying into objects, and dying on the streets. The incident sparked the interest of local resident Alfred Hitchcock, along with a story about spooky bird behavior by British writer Daphne du Maurier, helping to inspire Hitchcock's 1963 thriller The Birds, a cautionary tale of nature revolting against man.[23] The film is now ranked among the American Film Institute's top-10 thrillers of the last century.

Scientists looking at the stomach contents of turtles and seabirds gathered in 1961 Monterey Bay ship surveys have found toxin-making algae were present in 79% of the plankton[24] the creatures ate. "I am pretty convinced that the birds were poisoned," says ocean environmentalist Sibel Bargu of Louisiana State University. "All the symptoms were extremely similar to later bird poisoning events in the same area."

Plankton expert Raphael Kudela of USC points to leaky septic tanks installed amid a housing boom around Monterey Bay in the early 1960s as the ultimate culprit that may have fed the toxic algae:[25] "It is to some extent a natural phenomenon, and the best thing we can do is monitor for the presence of toxins, and treat impacted wildlife."

References
  1. BirdLife International (2019). "Ardenna grisea". IUCN Red List of Threatened Species. 2019: e.T22698209A154440143. doi:10.2305/IUCN.UK.2019-3.RLTS.T22698209A154440143.en. Retrieved 12 November 2021.
  2. Gmelin, Johann Friedrich (1788). Systema naturae per regna tria naturae : secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Vol. 1, Part 2 (13th ed.). Lipsiae [Leipzig]: Georg. Emanuel. Beer. p. 564.
  3. Cook, James; Furneaux, Tobias (1777). A Voyage Towards the South Pole, and Round the World : performed in His Majesty's ships the Resolution and Adventure, in the years 1772, 1773, 1774, and 1775. Vol. 2 (2nd ed.). London: W. Strahan and T. Cadell. p. 258.
  4. Latham, John (1785). A General Synopsis of Birds. Vol. 3, Part 2. London: Printed for Leigh and Sotheby. p. 435.
  5. Reichenbach, H. G. Ludwig (1853). Avium systema naturale. Dresden and Leipzig: Expedition der vollständigsten naturgeschichte. p. IV. The title page has 1850 (original title page missing in the BHL scan but available from BSB). The Preface is dated 1852 but was not published until 1853.
  6. Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (July 2021). "Petrels, albatrosses". IOC World Bird List Version 12.1. International Ornithologists' Union. Retrieved 3 February 2022.
  7. Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 40, 54, 179. ISBN 978-1-4081-2501-4.
  8. Austin, Jeremy J. (1996). "Molecular Phylogenetics of Puffinus Shearwaters: Preliminary Evidence from Mitochondrial Cytochrome b Gene Sequences". Molecular Phylogenetics and Evolution. 6 (1): 77–88. doi:10.1006/mpev.1996.0060. PMID 8812308.
  9. Heidrich, Petra; Amengual, José F. & Wink, Michael (1998). "Phylogenetic relationships in Mediterranean and North Atlantic shearwaters (Aves: Procellariidae) based on nucleotide sequences of mtDNA" (PDF). Biochemical Systematics and Ecology. 26 (2): 145–170. doi:10.1016/S0305-1978(97)00085-9.
  10. Austin, Jeremy J.; Bretagnolle, Vincent & Pasquet, Eric (2004). "A global molecular phylogeny of the small Puffinus shearwaters and implications for systematics of the Little-Audubon's Shearwater complex". Auk. 121 (3): 847–864. doi:10.1642/0004-8038(2004)121[0847:AGMPOT]2.0.CO;2. S2CID 86177092.
  11. Penhallurick, John & Wink, Michael (2004). "Analysis of the taxonomy and nomenclature of the Procellariiformes based on complete nucleotide sequences of the mitochondrial cytochrome b gene". Emu. 104 (2): 125–147. doi:10.1071/MU01060. S2CID 83202756.
  12. Rheindt, F. E. & Austin, Jeremy J. (2005). "Major analytical and conceptual shortcomings in a recent taxonomic revision of the Procellariiformes – A reply to Penhallurick and Wink (2004)". Emu. 105 (2): 181–186. doi:10.1071/MU04039. S2CID 20390465.
  13. "Proposal (647) to South American Classification Committee: Split Ardenna from Puffinus". South American Classification Committee. Retrieved 23 January 2016.
  14. McGonigal, David (2008). Antarctica: Secrets of the Southern Continent. Buffalo, NY: Firefly Books. p. 220. ISBN 978-1-55407-398-6.
  15. VanderWerf, Eric A. (2006). "Observations on the birds of Kwajalein Atoll, including six new species records for the Marshall Islands" (PDF). Micronesica. 38 (2): 221–237.
  16. "Longest Animal Migration Measured, Bird Flies 40,000 Miles a Year". Archived from the original on 2014-02-21. Retrieved 2013-10-19.
  17. Thayer, John E. & Bangs, Outram (1908). "The Present State of the Ornis of Guadaloupe Island" (PDF). Condor. 10 (3): 101–106. doi:10.2307/1360977. hdl:2027/hvd.32044072250186. JSTOR 1360977.
  18. Shaffer, S.A.; Tremblay, Y.; Weimerskirch, H.; Scott, D.; Thompson, D.R.; Sagar, P.M.; Moller, H.; Taylor, G.A.; Foley, D.G.; Block, B.A. & Costa, D.P. (2006). "Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer". PNAS. 103 (34): 12799–12802. Bibcode:2006PNAS..10312799S. doi:10.1073/pnas.0603715103. PMC 1568927. PMID 16908846. Supporting figures
  19. Carvalho, Paloma C.; Davoren, Gail K. (2020). "Niche dynamics of sympatric non-breeding shearwaters under varying prey availability". Ibis. 162 (3): 701–712. doi:10.1111/ibi.12783. ISSN 1474-919X. S2CID 203409303.
  20. Clark, T.J.; Bonnet-Lebrun, A.S.; Campioni, L.; Catry, P.; Wakefield, E. (2019). "The depth of Sooty Shearwater Ardenna grisea burrows varies with habitat and increases with competition for space" (PDF). Ibis. 161 (2): 192–197. doi:10.1111/ibi.12631.
  21. Corlett, Eva (9 July 2022). "'Like going back 1,000 years': ancient Māori bird hunt faces uncertain future". The Guardian. London, United Kingdom. ISSN 0261-3077. Retrieved 2022-07-10.
  22. Live Science. "Hitchcock's Crazed Birds Blamed on Toxic Algae". Livescience.com. Retrieved on 2013-04-03.
  23. American Film Institute. Afi.com. Retrieved on 2013-04-03.
  24. Vergano, Dan. (2011-12-28) Detroit Free Press. "Mystery of incident that inspired Hitchcock's 'The Birds' solved?" December 28, 2011. Freep.com. Retrieved on 2013-04-03. Archived January 7, 2012, at the Wayback Machine
  25. Kudela, R.; et al. (2005). "Harmful Algal Blooms in Coastal Upwelling Systems" (PDF). Oceanography. 18 (2): 184–197. doi:10.5670/oceanog.2005.53.

Further reading
  • Bull, John L.; Farrand, John Jr.; Rayfield, Susan & National Audubon Society (1977): The Audubon Society field guide to North American birds, Eastern Region. Alfred A. Knopf, New York. ISBN 0-394-41405-5
  • Harrison, Peter (1988): Seabirds (2nd ed.). Christopher Helm, London. ISBN 0-7470-1410-8
  • Gillson, Greg (2008): Field separation of Sooty and Short-tailed Shearwaters off the west coast of North America Birding 40(2): 34–40.
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