The vernal equinox, the first day of spring. The moment when the sun is directly above the equator, and day and night are nearly equal all over the world. Yet birds sense the growing hours of daylight through a surge of hormones. It’s time to sing! Both science and folklore tie spring to the renewal of nature, as the world awakens from the long cold winter. Listen carefully, and you might hear the bubbling song of a tiny Ruby-crowned Kinglet, or a Bewick’s Wren tuning up, or a towhee — like this beautiful Eastern Towhee — shouting out its whistled notes. Learn more at BirdNote.org.