April signals the beginning of the spring migration of birds. First, in the Deep South and Southwest as a trickle, but soon as a torrent as waves of warblers, thrushes, swallows, flycatchers, buntings, hummingbirds and waterfowl surge northward as the minutes of daylight increase throughout the Northern Hemisphere. By mid- and late-April, hundreds of millions of birds are on the move through North America, headed northward, ever northward.
Some migrants fly by night, others all day and all night, driven by the need to get to the breeding grounds, establish a territory, and attract mates.
Among the first to arrive in the North are the red-winged blackbirds, followed by robins, orioles, hummingbirds, and waves of wood warblers. Green oases, like Central Park in the heart of New York City, are migration hotspots. Tried and hungry warblers, tanagers, grosbeaks, vireos, and many others, stop to rest and feed in the green vegetation where insects, tree blossoms and leftover fruit and seeds restore the energy needed to complete the journeys. Refueling stations for migrating birds are also the millions of backyards across North America where thirsty passersby hesitate at bird baths, and hungry travelers stop for fruits, berries, mealworms and sugar water. Most will not stop, as they pass in waves of color through trees, shrubs and vines, in search of insects on fresh leaves and flowers.
Birders experience the passing parade with binoculars and field guide at the ready, and food, water and cover in place to delay the movement north, if only for a few seconds.
-- George H. Harrison