Skip to content
  • Home
  • About Us
    • About Us
    • About Our Staff
    • About Our Board
    • Our Commitment to Diversity
    • GGAS Code of Conduct
    • Strategic Plan
    • Annual Report
    • Job Opportunities
    • GGAS in the News
  • Blog
  • Osprey Cam
  • Contact Us
    • Contact Us
    • Join/Renew
    • Donate
    • Other Ways to Give
    • Planned Giving
    • Member Login
    • Corporate Partnerships
    • Violation Report
Golden Gate Audubon Society
Golden Gate Audubon Society
  • Education
    • Speaker Series
      • Past Speakers
    • Eco-Ed for Kids
    • Classes
      • Birding For Everyone Scholarship
    • Rotary Nature Center
  • Conservation
    • Conservation Info
    • Christmas Bird Counts
    • Bird-Friendly Coffee Club
  • Volunteer
  • Bird With Us
    • Birdathon 2023
    • Field Trips
    • Classes
      • Birding For Everyone Scholarship
    • Christmas Bird Counts
    • SF Bay Ospreys
    • Travel with GGAS
    • Birding Sites
    • Birding Resources
  • Archives
    • Trip Reports by Year
    • Past Speakers
    • The Gull Archives
    • GGAS Press Releases
    • Travel with GGAS – Past Tours
  • Log In
  • Donate
  • Become a Member
Golden Gate Audubon Society
  • Education
    • Speaker Series
      • Past Speakers
    • Eco-Ed for Kids
    • Classes
      • Birding For Everyone Scholarship
    • Rotary Nature Center
  • Conservation
    • Conservation Info
    • Christmas Bird Counts
    • Bird-Friendly Coffee Club
  • Volunteer
  • Bird With Us
    • Birdathon 2023
    • Field Trips
    • Classes
      • Birding For Everyone Scholarship
    • Christmas Bird Counts
    • SF Bay Ospreys
    • Travel with GGAS
    • Birding Sites
    • Birding Resources
  • Archives
    • Trip Reports by Year
    • Past Speakers
    • The Gull Archives
    • GGAS Press Releases
    • Travel with GGAS – Past Tours
  • Log In
  • Donate
  • Become a Member
 

Why birds in the coastal fog have smaller bills

  • August 22, 2012

By Jack Dumbacher 

Some bird species show tremendous geographic variation in plumage or body measurements.  For example, Fox Sparrows have a sooty Pacific form and a reddish Taiga form, Song Sparrows look different on the California coast than they do further north in the Pacific Northwest, and Dark-eyed Juncos – well, where does one begin…?

But most birders rarely consider that these subtle differences might be adaptations to local conditions. And it’s rarer still when there is scientific research suggesting how these differences evolve or make birds locally more fit.

Russ Greenberg, from the Smithsonian Institution’s Migratory Bird Center, has been studying differences in plumage and bill size in Song Sparrows and Swamp Sparrows for many years.  He has long understood that different populations of sparrows have significant variation in bill size and shape, but figuring out the evolutionary function of the variation has been difficult.

Greenberg’s research group recently made a huge breakthrough by examining how birds lose heat.  As we all know, birds’ bodies have a thick layer of feathers that provides superior insulation for heat and cold, so birds don’t lose much heat from their bodies.  However, birds’ exposed bills and legs can dissipate a great deal of heat.

Using stunning infrared photography, Greenberg and his colleagues showed that bird bills can work as an effective “radiator” that burns off excess metabolic heat [1].  And because radiating heat does not waste water from evaporation (as does panting or sweating), it is an especially effective means for dissipating heat in dry environments, such as our California deserts. Meanwhile, in cooler environments, a smaller bill may prevent heat loss, thus helping to keep the birds warmer.

Cold Sparrow: This image of an eastern Song Sparrow in a cold environment shows that the bill is 10 degrees above ambient temperature and is losing heat to the environment. Taken from Greenberg and Danner.

 

Warm sparrow: Eastern Song Sparrow imaged at 37 degrees C showing the bill and legs radiating heat to help cool the bird. From Greenberg et al.

So with this potential explanation, Greenberg’s team needed birds to study.  They turned to California Song Sparrows that are widespread and variable and live in a variety of habitats from the cooler coastal areas to the warm central valley, the Sierras and western deserts [2].  They measured almost 1,500 Song Sparrow bills from museum collections, including those at California Academy of Sciences and U.C. Berkeley.

They found an elegant correlation between bill size and average monthly high temperatures in the hottest month of the year.  Bird populations on the cool coast have smaller bills to prevent heat loss; those in the warmer regions have larger bills to dissipate heat and keep birds cool.

The results suggest that there is a basic amount of heat that sparrows lose through their body, and so the primary means of adapting to new temperatures involves changing their bill size.

Move over, Darwin’s Finches – bill size isn’t just about what you eat.

————————–

[1]  Greenberg, R., V. Cadena, R.M. Danner, and G. Tattersall, “Heat Loss May Explain Bill Size Differences between Birds Occupying Different Habitats.”  PLoS ONE, 2012. 7(7): p. e40933.

[2]  Greenberg, R. and R.M. Danner,  “The Influences of the California Marine Layer on Bill Size in a Generalist Songbird.”  Evolution, 2012.

—————————

Jack Dumbacher, a board member of Golden Gate Audubon Society, is Chair of the Department of Ornithology and Mammalogy at California Academy of Sciences.

PrevPreviousFirst of season
NextThe nymph Syrinx and Swainson’s ThrushesNext
Facebook Instagram Youtube Twitter

Follow Golden Gate Birder by email

Click to follow our blog and receive notifications of new posts by email.

Subscribe

Loading...
Audubon — the man and the meaning
March 24, 2023
Bay Birding Challenge Returns on April 1st
March 20, 2023
From new birder to Birdathon maven
March 15, 2023
The Audubon Name Issue Heats Up
March 8, 2023
One Step Closer to Bird Safe Buildings in Berkeley
March 3, 2023
San Francisco Christmas Bird Count 2022
January 18, 2023
Calling All CBC Yard Watchers
December 16, 2022
Meeker Slough
December 6, 2022
Lands End
December 6, 2022
Corona Hill
December 6, 2022

Our Mission

The Golden Gate Audubon Society engages people to experience the wonder of birds and to translate that wonder into actions which protect native bird populations and their habitats.

Home page photo of a Bald Eagle by Rick Lewis. Home page photos rotate on an occasional basis. If you have a Bay Area bird photo you would like us to consider, email us at rnakano@goldengateaudubon.org.

Home page bird illustrations by Tex Buss. We are grateful for her generous donation of time and talent!

Facebook Instagram Youtube Twitter

Contact Us

Golden Gate Audubon
2530 San Pablo Avenue, Suite G
Berkeley, California 94702

Phone: 510.843.2222

Office hours: Monday-Thursday, 10 a.m. to 5 p.m.

The Golden Gate Audubon Society  is a not-for-profit 501(c)(3) organization. Our federal tax ID number is 94-6086896

Manage your GGAS account online

Now you can manage all your GGAS business online — renew your membership, update your contact information, view past donations, or sign up for events such as classes, Birdathon or the Christmas Bird Count. Click here to access your account. (You’ll need to create a login name and password if you don’t have one already. If you forget your password, click on the “forgot your password” link.) You can also sign up for our new GGAS Chat to get updates on trips, talk with other members, and more!

© 2023 Golden Gate Audubon Society | All Rights Reserved
All photos on this site belong to the photographers and may not be used without written permission.
  • About Us
    • About Our Staff
    • About Our Board
    • Our Commitment to Diversity
    • GGAS StrategicPlan
    • GGAS in the News
    • Job Opportunities
  • Education
    • Speaker Series
      • Past Speakers
    • Classes
      • Rotary Nature Center
    • Eco-Ed for Kids
  • Volunteer
  • Conservation
    • Bird-Friendly Coffee Club
  • GGAS Archives
    • The Gull Archives
    • GGAS Press Releases
    • Travel with GGAS – Past Tours
    • Past Speakers
  • Bird With Us
    • Field Trips
    • Travel with GGAS
    • SF Bay Ospreys
    • Christmas Bird Counts
    • The Gull
    • Golden Gate Birder Blog
      • Birdathon 2021
    • Corporate Partnerships
    • Member Login
    • Trip Reports by Year
    • Contact Us
      • Join/Renew
      • Other Ways to Give
      • Planned Giving
    • Member Login
    • Volunteer Hours Reporting
    • Birding Resources
      • Conservation Info
  • Blog
  • Donate