While spring migration in the Adirondacks begins as a trickle in March and then grows through April, May is marked on the calendar of every birdwatcher in the North Country. They have waited through the cold and often quiet winter for this time of year when a windfall of migratory landbirds arrive enmass to the Adirondacks. Birds suddenly fill the woods and yards, just as they fill birders with joy. Many of these species will stay and breed for the summer, while others just pass through briefly.