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Dawn Chorus

2009 January 14

Each week we write about the science behind environmental protection. Previous Science Wednesdays.

photo of author, Karl Berg, in the field About the Author: Karl Berg is currently a Ph.D. student at Cornell University in Ithaca, NY, and is looking forward to a career that will combine his interests in animal behavior and conservation. His master’s research was funded by an EPA Science to Achieve Results (STAR) Graduate Research Fellowship.

Bird populations have long been viewed as “canaries in the coal mine” for indicating changes in environmental health. As EPA’s Report on the Environment states, “changes in bird populations reflect changes in landscape and habitat, food availability and quality, toxic exposure, and climate.” Because this is so important, annual bird counts to document population changes are conducted by the North American Breeding Bird Survey.

If the timing of the species’ calls is staggered, birds could be undercounted, which is why I wanted to find an improved method to monitor bird populations to better understand how they are changing and why.

closeup photo of colorful bird with blue rings around the eye In my quest to understand the “dawn chorus,”—why different bird species chime in at different times—I chose my research site in the tropical forests of Ecuador where hundreds of bird species occur together. Tropical forests are the most threatened terrestrial ecosystems on Earth and have large and diverse bird populations. As more forests are cut one immediate change that takes place in remaining forests is the quantity and quality of forest light.

My study showed that common communicative and reproductive behaviors of forest birds are synchronized or have co-evolved with seemingly tiny changes in forest light.

My wife and I spent several months trudging up muddy, forested mountains in a tropical rainforest of Ecuador at 4:00 AM to make over 100 hours of recordings, synchronized with twilight, to determine if the birds had a singing schedule.

closeup picture of birds headBack at Florida International University, we identified 130 bird species from the recordings and logged the times of 25,000 songs. My research showed that tropical birds began to sing only when they saw light. Big-eyed birds that foraged high in the forest canopy sang earlier. The late risers were birds with small eyes in the dark, dense underbrush. The control mechanism then, was a combination of ecological and morphological traits synchronized with an atmospheric one.

In the future, I believe that automated birdsong monitoring, supplemented by the sophisticated understanding of birdsong timing, will help EPA and others better understand our changing environment.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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7 Responses leave one →
  1. Lina-EPA permalink*
    January 14, 2009

    That’s fascinating! Good luck with your research. For how long did you travel through the rainforest? Notice any changes during that time?

  2. Brenda-EPA permalink
    January 15, 2009

    This is a great post! I never thought about how the sounds of the birds are related to daylight. Around our house here in the beautiful lush karst zone of Puerto Rico non-native”guacamayos” like to fly as the sun rises and make a lot of noise. I have noticed however that smaller native species prefer broader light while others like owls prefer the night. I will be on the lookout! I learned something new today!

  3. Marcus permalink
    January 15, 2009

    It took me years to figure out that bird ‘watching’ should really be called bird ‘listening.’ A good ear is far more important than good binoculars. It’s great to see that a good ear may now be a clever way to monitor environmental change.

  4. Linda permalink
    January 16, 2009

    Awesome work; I don’t think I’m up to long treks in the jungle these days, but I’m thrilled to read about your discoveries.

    I’m usually up and on my way to work before the sunrise, but on those rare days that I can catch it, I love to listen to the dawn chorus; I’m fortunate enough to live in an area where the sounds of the birds are often louder than the hum of distant traffic. It makes for a longer commute, but it’s worth it to me. I’ll keep on listening as long as I can.

  5. angeles permalink
    January 30, 2009

    Great article!!!!!!!
    Thank yoou.

  6. Karl permalink
    April 1, 2009

    Prior to to this project in 2002-03, I lived in coastal Ecuador between 1991-2001 and worked in several reserves during that time. When I first arrived to the region there were few forest reserves established and an alarming rate of deforestation. Today there is of course less forest but many more forest reserves and people working to protect them. Thanks for your interest and sorry for the delay.

  7. dissertation writing permalink
    July 20, 2009

    No doubt very helpful for the readers! Most of the posts in the blog sparks some great knowledge… Thanks for the information!

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