Today is the day. I mean, unless it’s raining. Then tomorrow is the day. Unless that day is raining, in which case it’ll be the next one. Anyway, what I mean is: this is the time when pine warblers show up.

For those blessed with a cluster of mature white pines in the neighborhood, a trill from the treetops will start any minute now. About the third weekend of April, whenever the night is calm or winds are from the south, in they come.

Inbound migration has been going on for several weeks. It was a short winter, and many early birds are earlier birds. I expected turkey vultures about the third week of March, but they started arriving about the second week. An eastern phoebe turned up on my porch April 1, a week sooner than usual. Ospreys were on the power poles next to the highway in Clinton on April 1. That’s when I customarily expect them, but a long winter delayed them last year.

April 1 is when I expect song sparrows and American robins to pop up and start singing. They joined the chorus right on cue. A few song sparrows can be found in southern Maine in winter, and robins can be found almost anywhere. But on one particular day during the first week of this month, suddenly every lawn seemed to be covered in robins and every roadside ditch was alive with song sparrows. A warm southerly breeze had swept them into the state overnight.

Yellow-bellied sapsuckers are early. They began popping up two weeks ago. Now, they are waking me up in the morning with a loud stuttering drum on the most resonant piece of metal or wood they can find.

Today is the day yellow-rumped and palm warblers return. Ruby-crowned kinglets arrive today. None of these may sing much until they settle onto a nesting territory, but they should all make enough noise to be noticeable. They’ll be hungry after that long flight, so trees may be alive with the movement of foraging flocks.

Some birds beat them here, but they’ve been sneaky. Hermit thrushes and winter wrens typically return to Maine in mid-April, but they don’t sing much until things warm up a bit. On the other hand, bluebirds are back and won’t shut up. Cowbirds came back last week, tree swallows this week.

Early returnees generally have one thing in common: they weren’t far away to begin with. Few of the early warblers ever left the country for the winter. Most of the yellow-rumps spent the cold months along the mid-Atlantic coast. A few hardy souls didn’t even leave the state. In January, I had two on Matinicus Island. One yellow-rump managed to survive the entire winter in Aroostook County this year. Pine and palm warblers skedaddle below the Mason Dixon line, but not much farther.

Hermit thrushes and winter wrens barely leave the state. I had one of each on Matinicus. While most other thrushes go to the tropics, some hermit thrushes may go no farther than Massachusetts. Killdeer make Virginia and Tennessee a winter home, and they’re back to Maine before the snow is gone. American kestrels share the same winter home with killdeer and return about the same time.

So the earliest birds have already arrived, and the early birds arrive today. Meanwhile, you’ve got about two weeks to re-learn what you know about bird songs. The rest of the warblers will start trickling in soon. Warblers that spent the winter in Florida will begin to arrive around the first of May. Black-and-white warblers have a winter range that extends all the way from the Gulf Coast states to Peru, and it’s a safe bet that the closest ones will get here first.

When I walk the wooded trails in the Everglades in March, I encounter a few black-throated green warblers and northern parulas, so a few of those will be back in time for May Day. The rest winter on Caribbean islands or the northern tip of South America, and they will follow within a week.

You might guess that the birds will dribble in steadily. Guess again. For birds travelling a long distance, which is just about all of them, they will wait until conditions favor migration. Then, boom, they all go at once. One day, the woods are quiet. The next, noisy. This time of year, when winds are from the south, have morning coffee on the porch. Your friends may have returned overnight.

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.