I can see spring on the way, but not because of the weather. Last week’s 40-degree days were quickly followed by colder temps, and snow and ice remain.

Because this is Maine, spring needs to sneak in through a side door. And sneak she does. Gradually, I realized the lengthening days (it is still light out when I leave work – what a difference that makes in my attitude!), but I am only just noticing what the birds have realized weeks ago.

It was a mourning dove that first tipped me off. I had been hiking along a snowy forest trail when I heard the sad cooing this for which this bird was named. Rather than sounding mournful, however, to my ears it sounded like soft sighs of relief, and I smiled.

The melancholy-like song, “oahow, oo, oo, oo,” is most often sung by males that are trying to attract a mate. Many people hear it during early morning or late evening and mistake it for an owl’s hooting. The difference between the two is cadence and quality.

Owl vocalizations are staccato, quick and bold. The dove’s voice, on the other hand, seems to be created by indrawn whispers. The notes sound as if they are floating and gradually fading away.

It seems the dove is also capable of fooling people with its courtship flight. Noisily flapping his wings, the male takes off from his perch and ascends 100 feet or more with deep-wing strokes. He then descends by slowly circling on slightly down-turned wings. This is when his profile resembles that of a sharp-shinned hawk or American kestrel. It’s as if he tries to attract mate by imitating a raptor.

Fascinating.

The length of a male’s cooing is an indication of the beginning of nest-building. It is he who selects a site by giving a shortened version of his long courtship coo. In this way he calls to the female until she flies up to join him, after which he begins collecting nesting material to pass along to her. It seems he is so intent on starting a family; he actually may stand on her back and pass her the material over her shoulder, as if to hurry her along. He may even alight in the nest and rearrange it to suit himself.

The male shares equally in the raising of the young as well. He incubates the eggs from dawn to dusk, only being relieved at night by the female, who then incubates them until morning. Once the young hatch, both parents feed them “pigeon milk,” a highly nutritious liquid that is secreted by the lining of the crop. This substance has more fat and protein than either human or cow milk, and is only fed for three days. After that, regurgitated insects and seeds make up the bulk of the diet.

Distinguishing between the sexes isn’t difficult, although the differences are subtle. The male has a rosy tinted breast and a gray-toned head, while the female is drabber. Juveniles can be identified by the absence of the black spot behind their eyes, their shorter tails, and their breast feathers edged with a light buff color.

Chris Corio’s column on birds is published each Saturday. Corio, a volunteer at Fields Pond Nature Center in Holden, can be reached at fieldspond@juno.com