Great Shearwater (Puffinus gravis)

• Appearance: white head with dark brown cap, black beak and feet, white chest and belly, dark brown patch in center of belly, wings dark brown on top and fade to gray white, white underwings, dark brown tail

       ο Females larger than males, but have same coloration

• Length: 18-20 inches (about 1.5 feet)
• Wingspan: 42-45 inches    (about 2.5 feet)
• Status: common, could be vulnerable because of limited breeding range

• Habitat
  • Open ocean, stay above open water, occasionally return to shoreline to roost
  • Pelagic bird – spends much of its life over open water
  • Usually stay at least 50 miles off coast
  • Take shelter on land during large storms
  • Range extends from Greenland to southern tip of South America, may extend as far as coastal tip of Antarctica
    • This species is sometimes seen in coastal Europe and Africa as well
  • Shares range with sooty shearwater
• Diet
  • Feed on small fish, squid, and crustaceans that swim near surface of the water
  • Forages over open water
  • Unlike many other birds, great shearwaters have a great sense of smell, use smell rather than sight to detect prey
    • Shearwaters use their acute sense of smell to detect chemical signals released by algae as defense mechanism when fish/crustaceans feed on an algae-covered surface
  • Dive down at sharp angle to surface of water, enter up to a few feet down in water to catch prey
  • Great shearwater has large wingspan compared to body to help it perform skilled maneuvers over the water
  • Use wings to “swim” after prey up to 200 feet deep
  • Also scavenge fish scraps from fishing boats
  • Shearwaters have been known to consume PLASTIC
    • Common explanation is that shine of garbage in water attracts them
    • New studies suggest that as algae grows on sitting plastics, they actually emit a chemical called DMS (dimethyl sulfide), DMS is also released when algae are being consumed by animals that shearwaters eat – birds dive down and may not ever realize they ingested plastic
      • “Why Do Seabirds Eat Plastic? The Answer Stinks,” Kat Kerlin
        • https://www.ucdavis.edu/news/why-do-seabirds-eat-plastic-answer-stinks/
    • Although larger pieces of plastic can entangle marine and shoreline animals, smaller pieces are usually more dangerous because once they enter the stomach, they are not digested, and birds do not pass them
    • Metals are also dangerous because they poison animals if ingested – has neurotoxins (damage nervous system) and carcinogens (cause cancer)
• Migration
  • ‘Vagrant” bird – it does not stay in one place for long, this makes it hard to study
  • Look for warm waters – June travel from North-South Hemisphere, September travel opposite way
    • The North and South Hemispheres have opposite seasons based on the way the sun hits the Earth at a certain point in the year – shearwaters stay wherever it is “summer”
  • Follow Gulf Stream on east coast of U.S.
  • Migrate about 6,000 miles
    • Can travel about 700 miles in a single day
  • Cruise speed is about 30 mph, but can reach top speeds of at least 60 mph
• Nesting
  • Long breeding season – September to May
  • Nest in burrows on remote islands with wooded areas or large stretches of tall grass
    • Most commonly seen on Tristan da Cunha islands (about 10 million birds), but also common on Gough island (about 6 million birds), uncommon on Falkland islands
  • Social bird – forms large colonies
  • Only return to nest at night
  • Both parents care for young
  • Juveniles learn to fly at about 70-90 days
  • Not much else is known about this bird’s life cycle
  • Average lifespan unknown, but oldest great shearwater was 55 years old