For us who have known the frigid mornings, the deep February snow and the short dark days in long shadows, the melody of the first songbird of spring is a joyful moment not soon forgotten. It is the bright promise of the new season.

I experienced that moment on March 25, when from somewhere far off within the matrix of tree limbs silhouetted against the glow of the fading evening sun came the song of a single robin. It sang early in the spring, as robins will do; faint at first, then rich and clear. Its fluid notes sounded like melting ice, and I knew that somewhere in the darkening sky more songbirds were on their way.

In fact, thousands of birds of all kinds are taking to the sky and flying beneath the stars back to our region to join the robin in proclamation of the breeding season. Although some birds migrate by day, the majority of songbirds fly here by night.

Finding the answer to why birds migrate at night has not been so easy for ornithologists; however, through observation of daytime hawk migration one explanation seemed clear. At midmorning when most nocturnal migrants are resting, hawks are floating effortlessly in circles above them on their migration routes. They are riding the updrafts of warming air masses or thermals, which allow them to soar efficiently without expending all their energy.

It is this energy, created by the sun, that is precisely why, in part, so many non-soaring birds choose to migrate at night. For them, thermals mean turbulence, which demands more energy to fly through. Migrating in daylight also means there is the threat of hyperthermia. Night migration eliminates the threat of heat exhaustion and frees the migrant from having to land to recover. The night skies are generally free of the chaotic effects of the sun, providing smooth flying conditions.

Night migration makes foraging for food in daylight possible, too. Most neo-tropical migrants look for a suitable stop-over site just before sunrise, feed during the late morning, and then rest. They are safer from predation this way, a real problem when landing in unknown terrain.

These are just a few of the reasons why so many birds migrate at night. It seems other explanations have much to do with how they find their way.

For birders, night migration means we don’t see the birds en route but only find them at their stop-over sites. This is good news for us in New London County where hungry tired migrants arrive across Long Island Sound and settle down at the first green patches of land. Places such as Groton’s Bluff Point act as land bridges that attract migrants and make for great spring birding.

Whether you visit Bluff Point or another coastal site, be sure to get there early when the migrants descend from the night sky. Though many will take back to the sky a day later, some will stay to fill the morning air with song while the last snow bank from winter 2015 melts from memory.

Robert Tougias is a Colchester birding author. He is available for color presentations and will take your questions at rtougias@snet.net.