By mid March most of our resident songbirds have paired off and are engaged in courtship behavior. As far as we know, they have no personal feelings for one another. Rather, they are responding to the lengthening daylight, which triggers their instinct to breed.
Mourning doves huddle together in the trees while cardinals, house finches and blue jays (yes, even the macho jays) offer morsels of food to one another. Most birds are not monogamous but will stay together for the breeding season, cooperating to build the nest and feed their ravenous offspring. Once the young are independent, the parents go their separate ways; some birds, such as robins, will stay together long enough to raise a second brood.