People often say that spring “bursts” forth. But this seasonal change isn’t like flipping a switch. It’s more like a series of waves breaking slowly. Robins and bluebirds return north in March. During April, more songbirds migrate north from the tropics, adding to spring’s growing chorus. As late as June, birds such as Willow Flycatchers and this Mourning Warbler arrive from South America. By this time, those early robins may be feeding their second brood. For them, spring has been bursting for over three months.More info and transcript at BirdNote.org. Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.