Great Shearwater Diet and Size: Feeding Habits, Predators, and Measurements
The Great Shearwater (Ardenna gravis) is a remarkable seabird that undertakes one of the longest migrations of any bird species, travelling thousands of miles across the Atlantic Ocean each year.
These oceanic wanderers are known for their distinctive appearance and impressive flying abilities, playing a vital role in marine ecosystems.
This article talks about their dietary habits, physical characteristics, and conservation status, providing valuable insights into these fascinating seabirds!
Table of Contents
The Dietary Habits Of The Great Shearwater
Great Shearwaters are skilled hunters of the open ocean, employing various techniques to capture their prey in deep waters.
What Does A Great Shearwater Eat?
Great Shearwaters primarily feed on fish and squid, which they catch by plunge diving up to 2 metres deep into the ocean. Their diet also includes small crustaceans and occasionally fish offal from fishing vessels.
These birds are opportunistic feeders, often following fishing boats to scavenge discarded fish. They are known to gather in large, noisy groups during these feeding sessions, showcasing their social nature when food is abundant.
Their hunting technique involves a combination of surface seizing and plunge diving, allowing them to exploit different prey depending on availability and ocean conditions. They are particularly active during dawn and dusk when their prey tends to be closer to the surface.
What To Feed A Baby Great Shearwater?
Baby Great Shearwaters are fed regurgitated fish and squid by their parents. The parents alternate feeding duties, making long foraging trips to gather food for their chick.
The chicks receive a diet rich in oils and proteins, essential for their development and the formation of waterproof feathers. Parents continue feeding their single chick until it reaches fledging age, approximately 80 to 90 days after hatching.
Breeding Habits Of Great Shearwaters
Great Shearwaters have unique breeding behaviours adapted to their oceanic lifestyle.
Do Great Shearwaters Mate For Life?
Great Shearwaters typically maintain long term pair bonds, often returning to the same nesting sites year after year. However, they are not strictly monogamous for life, and pairs may change if breeding success is poor.
These birds breed on remote islands in the South Atlantic, particularly in the Tristan da Cunha archipelago. They nest in burrows, which they either dig themselves or modify from existing ones, working predominantly at night to avoid predation.
The Size & Weight Of Great Shearwaters
Great Shearwaters are substantial seabirds with impressive dimensions suited to their oceanic lifestyle.
How Much Does A Great Shearwater Weigh?
Adult Great Shearwaters typically weigh between 715 and 950 grams. This weight range allows them to maintain the perfect balance between efficient flight and diving capabilities.
Their weight can fluctuate throughout the year, particularly during their long distance migrations when they may lose body mass. They regain weight during periods of abundant food availability.
How Big Is A Great Shearwater?
Great Shearwaters measure 43 to 51 centimetres in length, with an impressive wingspan ranging from 100 to 118 centimetres. These dimensions make them well adapted for long distance flight and ocean soaring.
Females tend to be slightly smaller than males, though this difference is not readily apparent in the field. Their size allows them to handle challenging ocean conditions while maintaining efficient flight during their extensive migrations.
Are Great Shearwaters Under Threat?
Great Shearwaters are currently classified as Least Concern on the IUCN Red List, though they face several conservation challenges. Their main threats include plastic pollution, fishing gear entanglement, and climate change impacts on marine ecosystems.
What Eats A Great Shearwater?
Adult Great Shearwaters have few natural predators at sea, but they are vulnerable to skuas and large gulls.
Their eggs and chicks face predation from rats and mice on breeding islands, particularly where these invasive species have been introduced.
Where Can I See Great Shearwaters In The UK?
Great Shearwaters can be observed in UK waters primarily between August and October, particularly off the southwest coast. The best viewing opportunities are during seabird watching trips from coastal locations in Cornwall, the Scilly Isles, and southwest Ireland.
These birds are typically seen during their northward migration, when they move through British waters following their figure of 8 migration pattern across the Atlantic. Stormy conditions can sometimes push them closer to shore, providing excellent viewing opportunities for birdwatchers.
SEE ALSO: Great Shearwater Life Cycle: Nest Building To Fledging (and everything in between)
Frequently Asked Questions
Great Shearwaters can reach speeds of 30 to 40 miles per hour during regular flight, but they can achieve higher speeds when riding ocean winds and currents.
Great Shearwaters typically live between 15 to 20 years in the wild, though their survival depends heavily on ocean conditions and food availability.
Yes, Great Shearwaters undertake one of the longest migrations of any bird, travelling over 14,000 kilometres in a figure of eight pattern across the Atlantic Ocean annually.
Great Shearwaters can dive up to 2 metres deep to catch their prey, though they typically feed closer to the surface.
