Bar-tailed godwits can fly about 12,000 km at one time – further than any other known bird. This recent discovery excited ornithologists1 around the world. Dr Phil Battley from Massey University’s Ecology2 Group and PhD3 student Jesse Conklin (now Dr), have been tracking and researching godwits’ flights from New Zealand.
The flight path
The researchers found that godwits leave New Zealand from various estuaries4 (Manawatū, Miranda, Golden Bay, Christchurch, Otago and Southland) from the second week of March to the end of the month. It seems they fly direct from New Zealand to eastern Asian estuaries (Japan, Korea and China). The birds leave Asia for breeding grounds in Alaska in May. After breeding, they refuel on the coastlands of south-western Alaska (Yukon-Kuskokwim delta and Alaska Peninsula). They then return to New Zealand on a non-stop flight across the Pacific Ocean, taking 7–9 days, from September to mid-October.
Preparing for flight
To prepare for the flight, the godwits need fuel5. The average godwit normally weighs about 300 grams. After fuelling for the trip, they weigh about 600 grams – doubling their weight6 in fat. Even their kidneys, liver7 and intestines shrink to make room for more fat (so they don’t exceed maximum weight for efficient flight). Their fuel (food) is predominantly marine polychaete worms, which they extract from muddy sediments8 using their long bills. They also eat small bivalves9 and crabs.
While in New Zealand, birds also replace their flight feathers10, growing new ones so that they will be strong enough to last them 30,000 km flight.
You can tell if godwits are getting ready to take off on migration. They become more active than usual, walking around, fluffing their feathers, having a bath and calling to others with a very distinctive call – it’s as if they’re asking the others who else is coming on this trip. They leave in groups.
The flight
Godwits fly extraordinary distances yet they aren’t particularly different from other migrating birds. It’s just that they do everything really well. Structurally, they have a wing shape designed for fast, efficient long-distance flight. Their feathers are very sleek so that the wind can pass over as smoothly as possible.
The birds also counteract wind resistance11 (drag12) by flying in flocks. The benefit of flying in a flock is that they fly in a V-formation. This means the bird at the front cuts into the wind first so that there is less wind resistance for the other birds. This makes flying easier for them, and as a result, the whole flock benefits by not becoming so exhausted. The birds have turns at taking the lead because the lead bird encounters the most drag and has to work the hardest.
Godwits fly at about 60 km/h, flapping their wings most of the way. They do not have completely waterproof feathers, so they can’t stop for a rest at sea. During the flight, they use up the fat they have stored plus some of their muscle13 tissue, which increases before the flight to cope with their extra weight. As they get lighter, the muscles do not need to work as hard and therefore don’t need to be as big.
Migration timing
In his PhD research, Jesse explored the relationship between when godwits leave New Zealand and when they return. It appears groups of godwits return to New Zealand in the same order as when they left.
Jesse discovered that migration timing is linked to the breeding grounds in Alaska. The birds seem to know exactly when to leave, and they leave at much the same time every year.
Alaska is frozen over for about 6 months of the year. As it thaws out, millions of birds come from all over the world to breed. Each latitude14 throughout Alaska starts summer at a different time. The southern parts thaw first followed by the more northern parts. It appears godwits always go to the same breeding grounds.
The godwits that leave New Zealand in early March breed in the south, where the ice melts first, and birds that leave at the end of March breed in the north, where the ice melts last.
Nature of science
Sometimes it’s hard to get funding for science projects that don’t seem to have a benefit for people. Funding that enabled the discovery of godwits’ flight distances was initially granted because of a concern that godwits may spread bird flu around the world. Without this link to a benefit for people, the research may never have happened.
Related content
Dr Phil Battley and Dr Jesse Conklin are two scientists who study and track godwits.
Activity idea
In this activity, students explore the incredible flight of a special bird known as E7 to learn about the migratory flight of bar-tailed godwits from New Zealand.
Useful links
In Your flight itinerary has changed Dr Jesse Conklin shares his 14-year journey studying Bar-tailed Godwits.
Alison Ballance joins a team catching and tagging 45 godwits to find out the sleep secrets of the kuaka, find out more in this RadioNZ Our Changing World programme from March 2024.
Watch this fascinating documentary from the TVNZ Sunday programme, which followed a team from Pūkorokoro Miranda Naturalists’ Trust on their visit to DPRK – North Korea to count godwits in April 2018.
Visit the website of the Pūkorokoro Miranda Shorebird Centre.
- ornithologists: People who study birds.
- ecology: The study of the interactions of living organisms with each other and their environment.
- PhD: Abbreviation of Doctor of Philosophy – a degree normally obtained after a concentrated period of research. This is the highest level of degree that involves supervision by academic staff at a university.
- estuary: A partially enclosed body of water where freshwater mixes with saltwater from the sea.
- fuel: 1. A combustible substance that provides energy. 2. A body fuel such as fat, carbohydrates and protein that supplies energy for animals’ activities.
- weight: Force due to gravity acting on an object, measured in newtons.
- liver: A vital organ situated beside the stomach. It is the body’s largest internal organ and plays a major role in metabolism as well as other important and complex functions.
- sediments: Material that settles to the bottom of a liquid. In geology, it describes the solid fragments of inorganic or organic material that come from the weathering of rock and are carried and deposited by wind, water or ice.
- bivalve: 1. Any mollusk, of the class Bivalvia, which has a soft body within two hinged-shells. Examples include mussels, oysters and scallops. 2. Having two similar parts hinged together.
- flight feathers: Long, stiff, asymmetrically shaped but symmetrically paired feathers on the wings or tail of a bird. Those on the wings are called remiges while those on the tail are called rectrices.
- resistance: 1. The opposition to the flow of electric current through a circuit. 2. The ability to withstand harmful or unfavourable conditions, such as an infectious disease.
- drag: Sometimes called air resistance or fluid resistance, drag refers to forces that oppose the relative motion of an object through a fluid (a liquid or gas).
- muscle: The tissue that makes it possible for an animal to move and to maintain its posture. Muscles also make the heart beat, force blood to circulate and move food along the digestive system. The human body has more than 600 muscles.
- latitude: A geographic co-ordinate that specifies the north-south position of a point on the Earth’s surface. Lines of constant latitude (or parallels) run east-west as circles parallel to the equator. Latitude is used with longitude to specify the precise location of features on the surface of the Earth.
