This is Bird Note.

We often hear it said that spring bursts forth as if winter is leafless trees suddenly

shimmer with green.

Flowers pop, birds start singing with all their hearts.

But this seasonal change isn't instantaneous, it's a series of waves, slowly breaking waves

that sweep up from the south to the north right over the continent.

Early spring migrants like Robbins and Bluebirds return north in March, some even in February.

Across the whole of April, week after week, new songbird migrants work north from the

tropics, adding bit by bit to spring's ever-growing soundtrack.

By May, birds continue flooding into northernly states in Canada.

And even as late as June, birds like Willow flycatchers and morning warblers are just completing

the trek to northern breeding sites from South America.

By this time, those early Robbins may already be hard at work feeding their second brood.

For them, spring has been bursting for over three months.

For Bird Note, I'm Mary McCann.