Quick Answer
The main types of birds that fly in a skein formation are geese and ducks. Skeins are the distinctive V-shaped flocks these birds form while migrating. The skein allows the birds to fly long distances efficiently by reducing air resistance. The lead bird breaks the headwind, allowing the birds behind to conserve energy as they ride the updraft. When the lead bird tires, it rotates to the back of the V while another takes the front position.
What is a Skein?
A skein is the recognizable V-shaped flying formation of migrating birds like geese, ducks, and some other waterfowl. The skein formation allows these birds to fly long distances with the least effort as a group.
The lead bird flies at the front of the V shape breaking the headwind. This creates an updraft behind it. The other birds fly slightly above and behind the lead bird, riding the updraft and avoiding the full force of wind resistance. This allows the trailing birds to conserve energy and fly with less effort.
When the lead bird tires, it will rotate back into one side of the V while another bird takes over the front position. The birds take turns cycling from the front to the back of the skein, which allows them to maintain the formation over long migrations.
The inverted V shape creates a short, efficient route for each bird while maximizing the lift from airflow. The shape is believed to allow the birds to communicate and coordinate while flying at a fast pace. Skeins may include just a few birds up to hundreds flying together in formation.
What Types of Birds Fly in Skeins?
The most common types of birds that fly in skeins are:
Geese
Geese are one of the most well-known birds to fly in a skein formation. Canada geese and snow geese especially are sighted frequently flying in V-shaped flocks across the sky during their migrations.
Ducks
Many duck species also flock and migrate in skeins including mallards, pintails, wigeons, teals and other common ducks. They form orderly skeins and swap the lead position while flying south for winter and north for summer.
Swans
Large birds like trumpeter swans sometimes migrate in smaller skeins with their young. Mute swans may also form some loose skein formations, especially small family groups led by the cob (male swan).
Cranes
Some crane species like the endangered whooping crane fly in crafty, sparse skeins during seasonal migrations often led by elders. Sandhill cranes may also occasionally form into a loose V-shape in the right conditions.
Pelicans
Flocks of American white pelicans and brown pelicans may sporadically organize into basic skein arrangements during migrations. However, they most often fly in straight lines or amorphous groups.
Benefits of the Skein Formation
Flying in a skein formation provides a range of benefits that help birds migrate efficiently over immense distances:
Aerodynamics
The V shape significantly improves aerodynamics for the flock. The lead bird breaks the headwind while the others ride the updraft, reducing drag and allowing them to fly faster with less effort. Evolving to fly in skeins allows birds to migrate extremely long distances.
Energy Saving
Birds flying in the skein formation save a significant amount of energy. Studies estimate that birds may conserve up to 20% of their energy by drafting in the skeins rather than flying independently. This energy saving is vital for powering their long migrations.
Communication
The skein allows birds to communicate during flight through vocalizations or visual cues. This lets them coordinate speed, direction and positional rotations. Birds alert each other to dangers or resting spots.
Navigation
Experienced adult birds guide the flock along migration routes in the front and rear positions of the skein. The formation helps them navigate and stay on course to reach their destination.
Thermoregulation
Flying together in close formation allows birds to share body heat and stay warmer in cool temperatures at high altitudes during migration. Warmth reduces energy expenditure.
How Do Birds Coordinate Flying in a Skein?
Flying in coordinated skein formations requires complex signaling and communication between birds:
Lead Bird
The lead bird guides the flock and breaks the headwind. It initiates changes in speed or direction. Leads vocalize to signal position shifts.
Position Shifts
Birds cue each other with honks or other calls as the lead bird prepares to rotate back from its tiring position. The new lead accelerates to the front point of the V.
Spacing
Birds space themselves close enough to gain lift from the updraft but avoid collisions. New flyers learn the optimal position from older flock members.
Velocity Matching
The skein coordinates speed, staying in sync by keying off the lead bird’s velocity. Sudden movements could disrupt the crucial formation.
Navigation
Experienced veterans fly at the front and rear to guide the flock’s navigation along traditional seasonal routes. Their knowledge keeps the skein on course.
Interesting Facts About Skeins
Some fascinating facts about the skein flying formations of migrating birds:
- The V shape optimally fits aerodynamics of flapping wings – birds don’t create perfect triangles.
- Geese fly in a steeper V formation than ducks and other waterfowl.
- The most effortful positions are at the front and very back of the skein.
- Fighter pilots use V formations inspired by migrating birds to reduce drag.
- Large skeins may have subgroups arranged in adjoining V shapes.
- Swans adopt loose, informal skeins – unlike the precise formation of geese.
- Birds communicate headings and resting stops to the skein through honking.
- Migrating birds likely rely on the earth’s magnetic fields to help guide navigation.
- Younger inexperienced birds learn skein positioning from older flock members.
- Larger birds create stronger uplift – allowing them to lead mixed flocks.
Conclusion
In summary, skeins are the distinctive V-shaped flocks formed by migrating birds like geese, ducks, swans, cranes and pelicans. The skein allows them to draft off each other, reducing wind resistance and saving vital energy. Birds coordinate position changes and velocity matching through vocalizations and other signaling. The skein formation provides crucial aerodynamic, energetic, navigational and thermoregulatory benefits that allow birds to complete their long seasonal migrations.