Category: Birds

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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.Why Some Birds Flock in the Vee Formation

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.

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

Video:

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

Van Ijken, Jan, Flight of the Starlings, National Geographic, Nov 15, 2016, https://youtu.be/V4f_1_r80RY
See also https://www.janvanijken.com/film-projects/the-art-of-flying/theartofflyingfullversion/

Additional Reading:

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

  • 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. https://www.researchgate.net/publication/51242928_Flying_in_a_flock_comes_at_a_cost_in_pigeons

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

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Dark-eyed Juncos

Click for a larger view of a Dark-eyed 'Oregon' Junco Male, Junco hyemalis montanus, Courtesy and copyright 2008 Ryan P. O'Donnell
Dark-eyed Junco “Oregon” Male
Junco hyemalis montanus
Courtesy & © 2008 Ryan P. O’Donnell 

Click for a larger view of a Dark-eyed ''Oregon'' Junco Female, Junco hyemalis montanus, Courtesy and copyright 2011 Ryan P. O'DonnellDark-eyed Junco “Oregon” Female
Junco hyemalis montanus
Courtesy & © 2011 Ryan P. O’Donnell 

Click for a larger view of a Dark-eyed ''Pink Sided'' Junco, Junco hyemalis mearnsi, Courtesy and copyright 2011 Ryan P. O'DonnellDark-eyed Junco “Pink Sided”
Junco hyemalis mearnsi
Courtesy & © 2011 Ryan P. O’Donnell 

Click for a larger view of a Dark-eyed ''Cassiar'' Junco, Junco hyemalis cismontanus, Courtesy and copyright 2011 Ryan P. O'DonnellDark-eyed Junco “Cassiar”
Junco hyemalis cismontanus
Courtesy & © 2011 Ryan P. O’Donnell 

Click for a larger view of a Dark-eyed ''Gray-headed'' Junco, Junco hyemalis caniceps, Courtesy and copyright 2011 Ryan P. O'DonnellDark-eyed Junco “Gray-headed”
Junco hyemalis caniceps
Courtesy & © 2011 Ryan P. O’Donnell 

My backyard bird feeders are a busy place this time of year. I enjoy keeping track of who visits – especially as a relative newcomer to the Utah bird scene. Last winter, however, I was baffled by the identity of what turned out to be a fairly ordinary bird.

Dark-eyed juncos are a common sight throughout the United States, but as it turns out, they exhibit an incredible geographic variation in plumage colors. There is a ‘slate-colored race’ which I was used to seeing in the Midwest – uniformly gray above with a white underbody. During Utah winters, the ‘Oregon race’ is common, with its black hood, brown back and peachy sides. Another ‘gray-headed race’ sports varying shades of gray with a distinct reddish brown patch on its back.

Depending on who you ask, there are up to fifteen different races, also called sub-species, of dark-eyed junco – all quite visually distinct, but all considered to be the same species. It wasn’t always this way, however. In the late 1950’s what we now call dark-eyed juncos were recognized as four different species, and in the 1890’s there were six.

These changes beg the question, at what point does speciation occur? And the answer lies in the ability of these birds to interbreed. One scientific definition of a species is those organisms or populations of organisms that are “potentially capable of interbreeding.”

Unique plumage patterns have evolved in a number of geographic locations across the junco’s range, however all of the dark-eyed junco variants could potentially interbreed if they happened to meet. Indeed in places where these geographic territories overlap inter-breeding does take place resulting in blends of the usually-distinct color patterns.

Juncos aren’t the only bird species with recognized color variants. Any raptor enthusiast will be familiar with variations in plumage colors that many birds of prey exhibit, such as merlins and red-tailed hawks. What makes dark-eyed juncos unique is that they are being studied as a possible case of speciation in progress. It turns out that there is more than just a difference in color among dark-eyed juncos. Some sub-species also exhibit variation in song patterns, social behavior, body size, and migration patterns, any of which may eventually cause these groups to stop interbreeding and allow a new species to emerge.

To see pictures of dark-eyed junco subspecies, visit our website at www.wildaboututah.org. Thank you to Rocky Mountain Power Foundation for supporting the research and development of this Wild About Utah topic.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:

Photos: Courtesy & © Ryan P. O’Donnell
Text:    Andrea Liberatore, Stokes Nature Center, logannature.org

Additional Reading:

Atwell, J.W., O’Neal, D.M, and Ketterson, E.D. (2011) Animal Migration as a Moving Target for Conservation: Intra-species Variation and Responses to Environmental Change, as Illustrated in a Sometimes Migratory Songbird. Environmental Law. Vol. 41:289 p. 289-319, https://www.amazon.com/Animal-migration-moving-target-conservation/dp/B005C29H7I

Alderfer, Jonathan (editor) (2005) National Geographic Complete Book of Birds. National Geographic Press. Dark-eyed junco information available online at: https://animals.nationalgeographic.com/animals/birding/dark-eyed-junco/

Cornell Lab of Ornithology, All About Birds: Dark-eyed Junco. https://www.allaboutbirds.org/guide/Dark-eyed_Junco/id/ac

History of Name Changes for Juncos. Cornell Lab of Ornithology. https://www.birds.cornell.edu/pfw/News/junco_taxonomy.pdf

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Til Death Do Us Part

Audio:  mp3 Listen to WildAboutUtah

Tundra Swan Pair
Cygnus columbianus
Courtesy US FWS
Tim Bowman, Photographer

Hi, I’m Holly Strand.

Each year we celebrate Valentine’s Day by expressing our love and devotion to a significant other. While humans are the only species that actually celebrate it, we aren’t the only animals who bond together as couples. Monogamy–or long term pair bonding as animal behaviorists call it–is practiced by over 90 % of birds. Along with a modest number of mammals, including wolves, beavers, voles and gibbons. Even a few fish pair up.

Monogamy may have evolved for different reasons among different groups of animals. For some, female dispersal may have played a role. If females are few and far between–as is the case with white tail ptarmigans–there is a tendency to pair up. Perhaps additional potential mates are too far away too bother. For males, monogamy can save a lot of time and energy. Monogamous males don’t have to fight over females or bother with first time courtship rituals. And by closely guarding a single female , males can protect their genetic investment.

There are advantages for females too. With a mate, you can get a little assistance around the nest or den. Male partners can help incubate eggs, guard against predators and help feed the kids. The fact that male and females are equally suited to care for chicks may explain why monogamy is so much more common among birds. The male improves his chances for reproductive success by investing in just one female’s little ones. The situation is different in mammals. Mammal males just can’t step in and help as much with gestation and lactation. So perhaps that’s why only 3% of mammal species form pair bonds.

The offspring of monogamous pairs tend to be pretty helpless at birth. Having two caregivers means that the you can take more time to mature. This long, slow development leads to larger brain sizes. Humans demonstrate this phenomenon very well as we parent our children longer than any other species on earth!

The tundra swan is Utah’s best example of monogamy in the wild. Young tundra swans date around a bit when they are young, but they eventually settle down with a single mate for life. They build and defend a nest together and raise the kids. But then they stick together the rest of the year as well. Greetings and courtship rituals such as head bobbing and dipping and ritual bathing strengthen their commitment toward each other.

You can see these beautiful swans in massive numbers twice a year when they migrate through Utah. Tens of thousands of them stop by the Great Salt Lake on their way to either the Arctic tundra or to central California.

For sources, pictures, and archives of past programs, go to www.wildaboututah.org

For Wild About Utah, I’m Holly Strand.

Credits:

Image: Courtesy US FWS, images.fws.gov
Text: Holly Strand

Sources & Additional Reading

Limpert, R. J. and S. L. Earnst. 1994. Tundra Swan (Cygnus columbianus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: https://bna.birds.cornell.edu/bna/species/089

Mocka, Douglas, and Masahiro Fujiokab. 1990. “Monogamy and long-term pair bonding in vertebrates” Trends in Ecology & Evolution. Volume 5, Issue 2, February 1990, Pages 39–43

Reichard, Ulrich and Christoph Boesch. 2003. Monogramy: mating Strategies and Partnerships in Birds, Humans and Other Mammals. Cambridge University Press.

Schultz, Susanne and Robin I.M. Dunbar. 2010. “Bondedness and sociality”
Behaviour, Volume 147, Number 7, 2010 , pp. 775-803(29).

Schultz, Susanne and Robin I.M. Dunbar. 2010. Social bonds in birds are associated with brain size and contingent on the correlated evolution of life-history and increased parental investment. Biological Journal of the Linnean Society. Volume 100, Issue 1, pages 111–123, May 2010.

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Hearts

Hearts abound this time of year – gracing cards, storefronts, and of course, chocolates. And while the heart symbol bears little resemblance to the organ itself, their abundance of late has caused me to consider my own heart, beating away largely unacknowledged all these years.

In its simplest form, the heart is a pump. Its sole function is to keep the blood in your body on the move, partnering with your lungs to deliver life-giving oxygen to each and every hard-working cell, from the top of your head to the tip of your pinky toe. Most hearts have two distinct features – an atrium where blood collects on its way into the heart and a ventricle which pumps the blood back out.

But even with these shared components, not all hearts are alike. Throughout the animal kingdom, hearts take on a variety of forms. Fish, for example, have a two-chambered heart: one atrium that collects blood and one ventricle that pumps it back out. Blood journeys from the heart to the gills, where it picks up oxygen and then continues on its way, delivering its cargo to the body before making its way back.

Amphibians and reptiles, with the exception of the crocodile, have a three-chambered heart consisting of two atria and one ventricle. One atrium is designated for the oxygen-poor blood that is headed towards the lungs while the other is reserved for oxygen-rich blood coming back from the lungs and headed out into the rest of the body. In the shared ventricle, blood from both atria mix slightly, resulting in a somewhat inefficient system that nonetheless seems to meet the needs of the animals it serves.

Mammals and birds have taken the heart one evolutionary step further with the development of a four chambered heart that fully separates oxygenated and deoxygenated blood. Blood flowing in from the lungs enters the left atria and is pumped out to the body by the left ventricle, while blood returning from the body enters the right atria and is pumped to the lungs via the right ventricle. Because of this total separation, the blood leaving a mammal’s heart contains more oxygen than a reptile’s – a huge metabolic advantage that helps support our warm-blooded fast-paced lifestyle.

Two-, three- and four-chambered hearts are considered closed circulatory systems, meaning the fluid, or blood, is fully enclosed within blood vessels. Insects, on the other hand, have an open circulatory system which means that they don’t have blood vessels at all. Instead their bodies are simply full of fluid that is continually circulated with the help of multiple simple hearts that pass liquid through as they contract and relax.

Lastly, there are some organisms that don’t need hearts at all! These creatures absorb oxygen through their skin and are small or thin enough that oxygen easily diffuses to all parts of the body. Some jellyfish, for example, have a body wall only two cells thick that separates their internal body space from the water around them.

Without our comparatively complex hearts, we probably wouldn’t be able to do what we do as humans and mammals. So take a moment during this Valentine’s season to acknowledge your amazing heart. Throughout the course of your lifetime it will beat upwards of 2 billion times and will pump as much as 100 million gallons of blood through its chambers. A pretty amazing feat for something we only celebrate once a year.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:
Text:     Andrea Liberatore, Stokes Nature Center in Logan Canyon.

Additional Reading:

Campbell, N.A. (1996) Biology, Fourth Edition. Benjamin/Cummings Publishing Company, Menlo Park CA

Bailey, Regina (2013) Circulatory System: Types of Circulatory Systems. https://biology.about.com/od/organsystems/a/circulatorysystem.htm

Meyer, J.R. (2005) Insect Physiology: Circulatory System. North Carolina State University. https://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html