The past two days we’ve had a male robin in our backyard who has been singing his heart out from one tree top and then another. He is calling for a mate (the mating call is quite different from the sound of a robin defending territory.
The first two pictures below are from a previous summer (hence the grass). The bottom two pictures show lover boy at work.
For more on robins see https://www.birds.cornell.edu/home/.
The Nature of Maine 