Male white-crowned sparrows around the San Francisco Bay Area exploited the sudden drop in anthropogenic noise when the region went on strict lockdown in April and May. From their field observations during previous years, the researchers had lots of data to show that urban birds sacrifice song quality for higher amplitudes—basically, they’re yelling to be heard in a noisy environment. When that din suddenly died down, the birds switched to songs that more closely resemble the softer, higher-quality calls of their nearby rural counterparts. – Wired