Each spring we anxiously await the first returning robin in the hope of warmer weather. That is a phenological event. It happens every year but the return date depends a lot on the weather. Migration and flowering are two more examples of phenological events. OK, here's your challenge.
Deciduous trees leaf out and create shade.
In Wisconsin, many dragonfly nymphs change into adults in the spring. Listen for a chorus of frog calls at dusk. In late May, watch for Karner blue butterflies to emerge from their cocoon-like chrysalis and feed on the nectar of wild lupine plants. Fuzzy yellow-brown sandhill crane chicks hatch this month. Watch the skies for warblers as they return from their winter habitats.