In the mountains where humans have disappeared, an eagle baby boom was occurring ─ The power of "silence" revealed by the COVID-19 pandemic

During the lockdowns of the COVID-19 pandemic, large wings quietly soared over the mountains where human presence had vanished.

The Bonelli's eagle, which claims the cliffs and gorges of Andalusia in southern Spain as its territory, experienced a "baby boom" during the 2020 lockdowns caused by the novel coronavirus, as revealed by long-term research from the University of Granada (UGR) in Spain.Phys.org

31 Years of Data Show the "Effectiveness of Silence"

The research team has been tracking the breeding of Bonelli's eagles in the province of Granada, southern Spain, for over 30 years. The study covered more than 1,200 breeding attempts, divided into three periods: pre-COVID (1994–2019), lockdown (2020), and post-COVID (2021–2024).Phys.org

Analysis of the extensive records revealed that the average number of fledglings per pair in 2020 reached the highest level in 31 years. Researchers pointed out that the lockdown led to a sharp decrease in human activity, coinciding with the

• late incubation

• chick-rearing period

, which is the most delicate time for breeding, resulting in an unusually quiet environment around the nests.Phys.org

They described this situation as a "natural experiment," a rare opportunity to compare the impact of human activity with a "human-free state."Phys.org

The Fact That "Humans Are Scarier Than Predators"

Interestingly, the study concluded that the improvement during the lockdown was not due to climate conditions or food availability, but rather the "presence of humans."

According to the research, the biggest hindrance to the breeding of Bonelli's eagles was not natural factors, but human activities such as:Phys.org

• Partridge hunting using decoys

  • Accidental shooting of adult birds and chicks near nests

  • Risk of lead poisoning from lead bullets

• Traffic from vehicles and recreational activities

  • Frequent human passage near nests due to hiking, mountain biking, and climbing

  • Increased time away from the nest due to continuous noise and human presence, raising the risk of chick mortality

The research team points out that partridge hunting using decoys, although a long-standing cultural practice in southern Spain, is actually prohibited under European law.Phys.org

In other words, the "greatest predator" for Bonelli's eagles was not other birds of prey or natural disasters, but humans themselves—a rather shocking message emerges.

Lockdown Was "Ideal Experimental Conditions"

Creating experimental "human presence/absence" conditions for rare species at risk of extinction is almost impossible both ethically and practically. Therefore, the lockdowns provided scientifically valuable comparative material.Phys.org

Since the early 1990s, the research team has been meticulously monitoring the territories of Bonelli's eagles annually,

• recording how many pairs successfully fledged chicks

• and how many chicks fledged per nest

as basic indicators of "breeding success."Phys.org

During the 2020 lockdown, researchers were able to continue field surveys thanks to special permission from the university. Without this permission, the chance to scientifically record "how birds changed in a human-free landscape" might have been lost.Phys.org

Thus, the combination of years of diligent monitoring and the serendipitous lockdown provided a concrete answer to the question,

"How well can Bonelli's eagles breed without humans?"
for the first time.

Researchers Seek a "Quiet Season"

The paper proposes two priority measures to protect Bonelli's eagles in the future:Phys.org

1. Ban on partridge hunting using decoys

   • Clarify that it is already illegal under European law and enforce effective regulations.

2. Restrict access near nests during the breeding season

   • During the breeding season, roughly December to May, regulate and guide hikers, cyclists, and climbers.

The research team stated, "Until now, we could only speculate on which measures would be most effective, but this study has scientifically established the priorities."Phys.org

Finally,

they emphasized that the responsibility to implement this lies not only with environmental authorities but with society as a whole,
calling for the creation of rules to "coexist" with nature rather than just "use" it.Phys.org

The "Memory of Silence" and "Boomerang to Humans" Spread on Social Media

When this news was reported, various reactions spread on social media. Here, we summarize the types of responses observed (specific account names are omitted, and content is rewritten).

1. Posts reflecting on "Humans were indeed the biggest source of stress..."

   Many recalled hearing birds more clearly in urban areas during the lockdown, realizing it wasn't just their imagination.
   Many felt confronted by the stress they impose on nature, with comments like "I'll walk more quietly next time I go to the mountains."

2. Realistic comments on "We can't replicate the lockdown, but..."

   We can't have another lockdown, but we can promote telework or reroute trails during breeding seasons to create partial "quiet times."
   Many posts considered realistic ideas on how to return "moderate quietness" to nature without halting society and the economy.

3. Threads with mixed opinions on hunting culture
   The proposal to ban partridge hunting using decoys sparked heated debates.

   • Voices saying "If it's illegal, it should be stopped immediately"

   • Counterarguments saying "Don't vilify traditional culture"

   • Compromise suggestions like "If it's to be preserved as culture, rules need updating, such as banning lead bullets and limiting locations"
     , leading to long threads.

4. Voices discussing the "link" with urban birds
   Some users cited previous studies showing increased bird sightings in urban areas in North America and Europe during lockdowns, noting, "It's not just about Bonelli's eagles."Popular Science
   Discussions linking the "comeback of nature" reported worldwide during lockdowns with this baby boom.

5. Summarizing with "We don't need another pandemic, but we want to keep this lesson"
   Finally, notable posts included

   "I never want another lockdown, but it's true that nature seemed happy then."
   "Can't we intentionally create a 'slightly quieter world' next time?"
   These posts suggested creating a wildlife-friendly environment through policy and lifestyle changes, rather than in exchange for disease.
   A positive summary advocating for creating a wildlife-friendly environment through policy and lifestyle changes, rather than in exchange for disease.

Considering Future Rules from the "Side Effects" of Lockdowns

Of course, no one wants to return to the pandemic itself.
However, this study provides concrete numbers showing the impact those months of forced societal slowdown had on nature.Phys.org

From this, we can learn points such as:

• Telework and digitalization can also contribute to nature conservation

  • Reducing commuting and travel can decrease "incidental leisure" in mountains and seas, creating rest periods for wildlife.

• A little creativity in the "timing, season, and route" of leisure can help endangered species

  • By closing specific trails only during breeding seasons or guiding routes to maintain a certain distance from nests, a "quiet core area" can be secured for birds.

• Traditional hunting and outdoor culture can be updated based on scientific knowledge

  • Instead of a binary choice between complete prohibition or preservation, there is an option to create "rules for coexistence" together, such as stopping the use of lead bullets or refraining during breeding seasons.

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