How do I know Spring is here?

Pussy-willows send out their downy canary blooms in otherwise empty forest edges.  The hooded mottled flowers of skunk cabbage emerge from muddy banks.  Early brown stoneflies crawl to shore, molt, and take flight, hovering over riffles as trout eagerly devour those that stray to slack water.  I become so absorbed in the movement of the stream that the swift whistling flight of two male common mergansers catches me off guard.  Song sparrows and red-winged blackbirds drown out the sounds of blaring canada geese in wetlands still cluttered with dormant cattails.  These are the first novel colors and movements of the year, revealed only by the absence of foliage, yet to conceal.