Birdbaths, Bugs, and Bird-health: parallels in the US and Amazon reveal the consequences of human activity on birds


by

Hannah Stewart

2021 Intern

I am a recent graduate of Millbrook School in New York and will be attending St. Andrews University. I grew up in rural Connecticut where I was raised to value and respect nature and find joy learning from it. Moving forward, I plan on studying Sustainable Development in the Sciences at university in an effort to apply my love feature and passion for science to pressing global and local issues.

Learn more about Hannah Stewart


August 9, 2021

Birdbaths, Bugs, and Bird-health: parallels in the US and Amazon reveal the consequences of human activity on birds

 

Birds drinking from bird bath

Busy birdbaths such as this could be dangerous transmission sites that enable the spread of the disease between bird populations. 

This May amidst the blossoming new life of spring, something ominous emerged. In the Washington D.C. area, veterinary offices and wildlife management centers’ phones were ringing off the hook with reports of dizzy, unresponsive birds with crusty, swollen eyes. The culprit: a new disease of unknown cause. 

3000 miles away in the depths of the untouched Brazilian Amazon, bird populations are also suffering. A look at bird populations in an area of preserved rainforest about 50 miles away from Manuas, Brazil revealed several species of birds that have become less abundant compared to previously recorded numbers. 

Although not directly related, these parallel instances of health decline in bird populations serve as a powerful reminder of the impact that human activity can have on ecosystems. An investigation into the root cause of each population’s plight reveals a valuable lesson about the possibility of the indirect consequences of negligent human behavior. 

As the disease continues to spread, residents of impacted areas are being urged to retire their birdbaths and feeders; places of congregation like backyard feeders can act as hotspots of infection as diverse groups of birds come together. 

In the US, the new disease has spread swiftly, with sightings and reports of sick birds popping up throughout the Mid-Atlantic and Southeastern regions of the country. Prominent among young Blue Jays, American Robins, and European Starlings, this disease affects many common songbird species that are beloved staples of backyards, parks, and forests throughout the US. As the disease continues to spread, residents of impacted areas are being urged to retire their birdbaths and feeders; places of congregation like backyard feeders can act as hotspots of infection as diverse groups of birds come together. 

The search for the cause of the mysterious and swift spreading disease is ongoing. Scientists and researchers continue to gather information about the transmission and symptoms of the illness.  However, beyond ruling out several common pathogens as the culprit, investigations into the cause are inconclusive. 

Meanwhile in the Brazilian Amazon, biologist Philip Stouffer and fellow researchers observed a noticeable decline in sightings of a variety of already rare birds in the depths of untouched forest. The results of an ensuing study tracking bird population numbers between 2006 and 2016 indicated 9 species have become at least 40% less common since the early 1980s; furthermore, it seems that eight of these nine are more than 50% less abundant. Notably, the species in decline were all insectivores as opposed to the fruit eating bird species, which boasted much more stable and even rising population levels.

Obviously, such a striking decline in numbers was concerning and indicative of an underlying issue, but the question that remained to be answered was: what is the issue? These species live in the midst of a sprawling and healthy section of the Amazon rainforest, surrounded by a seemingly unscathed environment, the birds ought to be thriving as well. 

Back in the States, the hunt for the source of the new disease continues. Although it is too soon to definitively state the cause, several hypotheses have been developed. One hypothesis that has gained traction is that the disease could be linked to the use of pesticides. The most recent cicada brood, ‘Brood X’, may be a food source for many birds and emerged from the ground around the same time that sightings of sick birds began. In an NPR interview bird ecologist, Brian Evans suggested that after 17 years under the ground the cicadas could easily be a cache of poisons such as pesticides. The neurological symptoms displayed in ailing birds could be linked to the consumption of toxin ridden insects. 


After 17 years in the ground the ‘Brood X’ cicadas emerged this spring and have become a new food source for wildlife, including many birds. 

For Stouffer and fellow scientists in the Amazon, the final step in their research was to identify the origin of the nine species’ population decline. In a paper published in 2020 in Ecology Letters, Stouffer and ten other authors offer an explanation linked to climate change. After rejecting several other possibilities, the paper argues that impacts from climate change such as lowered abundance of food sources (insects) are likely the cause of population decline.

With every action we take, we are not just directly, but indirectly affecting the animals around us.

These two snapshots of bird health from across the world, an unsolved mystery in the US and an alarming discovery in the Amazon, are harmonious notes to an ominous tune. With every action we take, we are not just directly, but indirectly affecting the animals around us. These two examples of declining health in bird populations are reminders of the valuable and complex systems of interaction that are the basis of life on earth. A disruption of these systems at any level can be detrimental; harmful chemicals found in pesticides passed from insect populations to birds could be a possible cause of the devastating illness in the US, likewise, in the Amazon, insect reduction caused by the climate crisis has thrown previously untouched bird populations into sharp decline. 

Whether the information in this post is shocking, or all too familiar, let it serve as a reminder of the impact you have on the ecosystems that you are a part of and recall that this impact also gives you agency to do good. 

Sources:

Brady, Jeff. (July 2,2021).“A Mystery Illness Is Killing Mid-Atlantic Songbirds.” NPR,  Retrieved from https://www.npr.org/2021/07/02/1012541984/a-mystery-illness-is-killing-mid-atlantic-songbirds

Evans, Brian. (June 28, 2021). “Correlation, Not Causation: Brood X Cicadas and Regional Bird Deaths.” NPR, Retrieved from https://www.npr.org/transcripts/1011043752

Grossman, David. (October 6, 2020). “Nine insect-eating bird species in Amazon in sharp decline, scientists find.” The Guardian, Retrieved from https://www.theguardian.com/environment/2020/oct/26/nine-insect-eating-bird-species-in-amazon-in-sharp-decline-scientists-find

Kindy, David. (July 16, 2021). “Mysterious Bird-Killing Illness Spreads to More Mid-Atlantic States.” Smithsonian Magazine,  Retrieved from https://www.smithsonianmag.com/smart-news/mysterious-bird-killing-illness-spreads-more-mid-atlantic-states-180978199/

Rubiano A, Maria Paula. (June 2, 2021). “Birds Are Declining in a Supposedly ‘Untouched’ Region of the Rainforest.” Audubon,  Retrieved from https://www.audubon.org/news/birds-are-declining-supposedly-untouched-region-amazon-rainforest

Stouffer, P.C., et al. (2021), Long-term change in the avifauna of undisturbed Amazonian rainforest: ground-foraging birds disappear and the baseline shifts. Ecol. Lett., 24: 186-195. https://doi.org/10.1111/ele.13628

Thompson, Joanna. (July 8, 2021). “Scientists Still Searching for the Pathogen Behind the East’s Songbird Epidemic.” Audubon,  Retrieved from https://www.audubon.org/news/scientists-still-searching-pathogen-behind-easts-songbird-epidemic

 

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