Why Some Birds Flock in the Vee Formation

Why Some Birds Flock in the Vee Formation: Canada Geese Flying in a V Formation. Courtesy & Copyright, Brenda Bott, Photographer
Canada Geese Flying in
a V Formation
Courtesy & Copyright © Brenda Bott, Photographer

Spring is that magical season when avian migrants return north from more balmy climates. Utah’s migrants range from ponderous pelicans to tiny hummingbirds, honking geese to crying curlews. Many arrive as they departed, in flocks.

(Kevin Colver: Songbirds of Yellowstone, Canada Goose)

But why fly in a flock at all? One reason is predator evasion, the same reason that minnows school and elk, bison and deer bunch in herds. Embedded in a swirling mass of birds called a swarm flock, an individual bird is less likely to be picked off by an aerial predator, such as a falcon or a Cooper’s Hawk. A raptor diving into a swarm flock risks collision and injury. Targeting a bird in a swirling group is visually difficult too. Flying in a flock gains safety, but at what cost? Pigeons flying in a swarm flock take shallower, more frequent wing strokes than a solo bird. Faster wing beats probably provide more control to better negotiate turbulent aerial traffic, but extra flapping costs more in energy.

In contrast, pelicans and other big birds often fly in tidy formation flocks. Flying in a vee formation, a trailing pelican’s heart beats 13% slower than the lead bird. That’s because a trailing pelican flaps less than the leader. Unlike pigeons, then, a pelican flying in a formation flock uses less energy, not more. Big birds with slow wing beats share aerodynamic attributes with airplanes. Some of the air under their wings swirls out from under the tips, creating a spiraling vortex that trails the wing tip. Flying in a tight vee formation, each trailing bird gets a bit of lift from the upwash created by that vortex, and so it can flap a little less and glide a little more. Lead birds tire more quickly, so leaders change periodically. Leaders lose their zip, not their way. In a vee, birds also have their flock mates in good view, which is needed for the tight precision of a formation flock.

(Kevin Colver: Songbirds of Yellowstone, Sandhill Crane)

Pelicans, swans, geese, cranes, ibis, ducks, godwits, they all ply the Utah sky in formation flocks. They may be bird-brained, but our bigger migrants know a thing or two about aerodynamics.

Images: Courtesy & Copyright Brenda Bott, Photographer
Text: Jim Cane, Bridgerland Audubon Society http://www.bridgerlandaudubon.org


Spectacular flock (called a “murmuration”) of starlings, Sophie Windsor Clive & Liberty Smith, http://www.youtube.com/watch?v=iRNqhi2ka9k As viewed from Islandsandrivers.com. Contains advertisements.

Additional Reading:

Avian flight by John J. Videler. 2005. New York, Oxford University Press. 258 pp.

  • Acquisition of knowledge
  • The flight apparatus
  • Feathers for flight
  • Aerodynamics
  • Evolution of bird flight
  • Bird flight modes
  • The bird flight engine
  • Energy required for flight
  • Comparing the metabolic costs of flight

Usherwood JR, Stavrou M, Lowe JC, Roskilly K, Wilson AM. 2011. Flying in a flock comes at a cost in pigeons. Nature. 2011 Jun 22;474(7352):494-7.

Weimerskirch H; Martin J; Clerquin Y; Alexandre P; Jiraskova S. 2001. Energy saving in flight formation. Nature. 413: 697-698. http://eol.org/data_objects/16885552

Heading South

US Flyways
Courtesy US FWS

Hi I’m Holly Strand.

Every fall, I scan the sky for the fluid lines of birds heading south to their winter homes. Although the flocks are fascinating to watch, I get a bit melancholy. I imagine the warm and balmy weather ahead of them and the frigid temperatures that are in store for me.

Migration behavior in birds –and other animals– evolved to help them cope with a scarcity of resources during a particular time of the year. Severe weather and lack of food are characteristic of winters in the far north of the Northern Hemisphere. Therefore almost all of the birds migrate. Although more hospitable than the arctic, Utah winters are no picnic. Therefore, birds that breed in Utah have also bought heavily into migration.

Huge numbers of Wilson’s Phalarope
gather at the Great Salt Lake
before migration.(female)
Photo courtesy and
Copyright © 2008 Stephen Peterson

Looking at a map of Western Hemisphere migration routes –or flyways—you might be reminded of the route map of a major airline. There are short regional flights, say to an adjacent state to the south or sometimes just to a lower altitude. There are medium distance flights to Mexico or Central America. And then there are the long haul flights, with birds flying from northern tundra all the way to Argentina, Chile or Antarctica.

Wilson’s phalarope is one of Utah’s long-distance migrators. After the breeding season, about 500,000 birds form the largest staging concentration of phalaropes in the world at the Great Salt Lake. After fueling up on brine shrimp and brine flies, the birds head off to wetlands in Bolivia and Argentina.

Huge numbers of Wilson’s Phalarope
gather at the Great Salt Lake
before migration.(male)
Photo courtesy and
Copyright © 2008 Stephen Peterson

Swainson’s hawk travels farther than any other North American hawk. It migrates to the Argentinian pampas in huge flocks with as many as 5,000–10,000 individual. If a Swainson’s hawk begins migration in the northern part of its range, total round trip distance will exceed 20,000 km.

The rufous hummingbird doesn’t breed in Utah but flies though on its remarkable journey from the northwest and Alaska to Central America. If you measure its travel in body lengths as opposed to distance, this tiny little aviator makes world’s longest known migration.

For pictures and sources please go to www.wildaboututah.org

Thanks to the knowledgeable folks on the UtahBirds chatline for their help in developing this story.

The Swainson’s hawk photographed
in Starr, UT will overwinter
in Argentina.
Photo courtesy and
Copyright © 2006 Lu Giddings

For Wild About Utah, I’m Holly Strand

Photo: Courtesy US FWS National Digital Library
Swainson’s Hawk: Courtesy and Copyright 2006 Lu Giddings
Text: Holly Strand

Sources & Additional Reading

Bechard, Marc J., C. Stuart Houston, Jose H. Sarasola and A. Sidney England. 2010. Swainson’s Hawk (Buteo swainsoni), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/265

With a length of 9.5 cm,
the rufous hummingbird
has the longest migration
in the world in relation to its size.
Photo courtesy and
Copyright © 2010 Michael Fish

Berthold, Peter. 2001. Bird Migration: A General Survey (second edition). Oxford Ornithology Series. Oxford University Press. http://www.amazon.com/Bird-Migration-General-Survey-Ornithology/dp/0198507879

Colwell, M. A. and J. R. Jehl, Jr. 1994. Wilson’s Phalarope (Phalaropus tricolor), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/083

Elphick, Jonathan, Ed. The Atlas of Bird Migration. 1995. NY: Random House. http://www.amazon.com/Random-House-Atlas-Bird-Migration/dp/0679438270

Healy, Susan and William A. Calder. 2006. Rufous Hummingbird (Selasphorus rufus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/053

A Rufous hummingbird
collects nesting material
Photo courtesy US FWS
George Gentry, Photographer

USGS. Northern Prairie Wildlife Research Center Migration of Birds. http://www.npwrc.usgs.gov/resource/birds/migratio
[ Accessed October 28, 2010]

Weidensaul, Scott 1999. Living on the Wind. NY: North Point Press http://www.amazon.com/Living-Wind-Across-Hemisphere-Migratory/dp/0865475911

Spring Migration

Dolichonyx oryzivorus
Courtesy: U.S. Fish & Wildlife Service
Steve Maslowski, Photographer

Hi, I’m Holly Strand from Stokes Nature Center in beautiful Logan Canyon.

As temperatures warm and spring flowers appear, Utahns will hear an increasingly diverse choir of twitters, whistles, chatters and coos filling the air. Continuing over the next few weeks, thousands of migratory songbirds will mingle with our year-round avian residents in fields, forests, and wetlands.

No road maps or GPS units guide these migrants to their desired destinations. Scientists continue to marvel at how the birds know exactly where to go. There is evidence that magnetic fields of the Earth, landmarks, the Moon and stars—even specific  odors– may guide their flight.

Most songbirds migrate during the night. Cooler air helps keep the birds from overheating.    Also, night air tends to be less turbulent, so birds are less likely to be blown off course.  Just like humans stuck in an airport, birds can be grounded for hours or days during bad weather.  Birds may die of hunger, fly into objects, or be eaten en route.  Obviously the benefits of the destination must outweigh the risk of travel or birds simply wouldn’t bother.

So where are these migrant birds coming from?  Well, not unlike some Utahns, many birds spend the colder months in Arizona or New Mexico.  Others overwinter south of the border in Mexico or Central America.

Bobolinks have one of the longest annual migrations of any North American songbird. These Neotropical migrants travel over 12,000 miles from their North American breeding grounds to their “wintering” grounds in Argentina or Paraguay. This means they spend about half of each year in migration. They typically arrive in Utah in early to mid May..  Even after such a long flight, there’s no time for rest.  The weary, soon-to-be- parents must busily prepare for the arrival of hungry offspring.   Then  around mid August or September it’s time for the long flight back to the southern hemisphere.

No longer common, bobolinks are now  spotted in isolated patches primarily in the northern half of the state.  Look for them nesting or  foraging in wet meadow and  grasslands, and irrigated agricultural fields.

Frank Howe and Mary-Ann Muffoletto provided text and background information for this piece.

Thanks to the Rocky Mountain Power Foundation and the  USU College of Natural Resources for supporting research and development of Wild About Utah topics.

For Wild About Utah and Stokes Nature Center, I’m Holly Strand.


Text: Stokes Nature Center: Holly Strand with text from Mary-Ann Muffoletto, Frank Howe