Nature Changes Faster Than We Imagine - Transforming in Just a Few Years: What the Pandemic Revealed About "Nature with Humans/Nature without Humans"

1) What Was the "Empty City" to Nature?

In 2020, the world suddenly became "quiet." Travel restrictions, campus closures, and the disappearance of tourism. While it was a crisis for humans, it created a massive "experimental condition" for living creatures. Scientists have referred to this period as the Anthropause, observing changes in the behavior, distribution, and reproduction of wildlife. Nautilus

However, the focus this time was not just on "behavior." There is a report that the very "shape of birds' bodies" changed and then reverted back . SMC España

2) The Protagonists: "Familiar Birds" Living in Cities

The subject of the study was the dark-eyed junco, a small bird widely seen in North America and observed in urban areas. The key point is that there was a long-term trackable population of this bird adapting to "urban life." Wikipedia

Urban birds have different food and environments compared to the "wild." Processed foods dropped by humans, trash bins, leftovers from outdoor meals—these resources change the survival strategies of urban creatures. In fact, it was suggested that before COVID-19, the beak shape of urban juncos differed from non-urban ones, potentially related to **human-derived food resources (such as leftovers of processed foods)**. Wikipedia

3) The "Rewind" of Beaks Triggered by Lockdown

According to an explanation by the Science Media Centre, this study compared data from before, during, and after the lockdown on a population in urban Los Angeles, showing that the size and shape of beaks changed "quickly" and "reversibly" . SMC España

Particularly symbolic is the point that the beaks of individuals born during the Anthropause shifted towards a shape closer to non-urban (wild environment) individuals . However, as campus activities and human presence returned, they reverted back to the "urban type" shape within a few years . SMC España

The sample size was not small. The explanation mentions measurements on a scale of 626 adult birds and 1,067 chicks . OUP Academic

4) What Moved the "Beak": Evolution or Plasticity?

The important thing here is not to jump to the conclusion that "a shape that changed in a short period = immediate evolution." The study indicates a phenomenon where morphology changes according to the environment and can revert , with multiple possible mechanisms.

• Developmental plasticity (phenotypic plasticity)
  If the type of food (hardness, granularity, nutritional composition) changes during the growth phase of chicks, the beak, as a feeding organ, may change its "growth pattern." If human activity decreases, access to leftovers and waste from processed foods becomes difficult, and the diet reverts to a more wild type—this makes it easier to explain the "rewind" during the Anthropause. SMC España

• Changes in population composition (immigration/emigration, differences in reproductive success)
  If human traffic decreases, movement within and outside the city, predation pressure, and nesting success also change. The average morphology can shift depending on which individuals increase or decrease.

• (If any) Changes due to selection
  However, considering the "reversion" within a few years, it is prudent to be cautious about explaining it solely through genetic fixation. This is why the interest of this study lies in presenting the fact that "urban environments might affect even the shape of bodies." SMC España

5) We Have Underestimated the "Urban Food Web"

Cities are not just concrete blocks; they are also massive "feeding devices." The way garbage is disposed of, the amount of outdoor dining, cleaning frequency, the structure of trash bins, and human density—all these elements shape the main course, side dishes, and desserts for birds.

A summary on Wikipedia notes the possibility that the difference in beak shape among urban individuals is related to a diet centered on "leftovers of processed foods eaten by people on campus," and that during the lockdown, they approached non-urban individuals and reverted after the lockdown was lifted. In other words, our "everyday eating and disposal habits" can influence the physical design of wildlife . Wikipedia

6) Reactions on Social Media: Surprise → Ethics → Debate on "Feeding"

When this kind of news spreads on social media, reactions typically deepen in three stages.

(1) First, surprise: "Can it change that quickly?"
The pure surprise of "Can the shape of the body change just because the number of people decreases?" has been repeated in discussions about the Anthropause in general. Nautilus

(2) Next, it hits: "So how much does the usual city change living things?"
The fact that it "reverted" highlights that human impact is not one-directional but closely tied to daily life. Here, many people begin to redraw the line between their own lives (dining out, garbage, pets, gardens) and the wild.

(3) And then to debate: "Is feeding good or bad?"
On platforms like Reddit, topics about bird health, infectious diseases, and how "feeding stations affect behavior and physical characteristics (beak shape)" are often discussed alongside personal experiences. In one thread, comments expressed surprise with **"beak shape! Really!"** while touching on the risk of disease spread among birds and the problem of feeding stations "attracting too many" birds. Reddit

In the same flow, a self-critical perspective emerges: "Even if we think we are doing good for the birds, isn't it more about human satisfaction?" Reddit

This is important. What this study suggests is not a simple conclusion like "let's stop feeding." Rather, the design of urban resources (waste management, outdoor dining, green space design) shapes wildlife , which is a larger point of discussion. SMC España

7) So What Can We Change?

The boundary between urban and wild is drawn more by "human behavior" than by laws or maps.

• Whether trash bins are open or closed

• Whether leftovers remain on the street or are collected

• Whether green spaces are "corridors" or "habitats"

These small differences might connect to changes in birds' feeding, reproduction, and even morphology as seen in this study. The Anthropause was a tragic era. Nonetheless, it was a period that made it clearer than ever that we are the "influencers." SMC España