Every spring the birds come to a sturdy yellow birch tree on the Boston Public Garden, a species of tree with which they must be familiar on their breeding grounds in the north. The sap flows plenteously in mid-April from the many punctures that the birds make; it wets a large portion of the trunk of the tree and often drips to the ground from the branches. The birds stand clear of the tree as they feed at the sap wells with only the feet and the tip of the tail touching the bark. The tail is braced against the trunk at an angle of about 45°, and the feet reach far forward to grasp the bark opposite the bend of the wing. I have never seen a sapsucker crouch against this wet bark as a downy woodpecker commonly does when digging out a grub—like a cat hunched up lapping a saucer of milk. When a bird wishes to move to a point below where it is perched, it jumps from the tree and floats in the air, then turning, with its wings held out somewhat, dives head-downward, drifting in an easy, leisurely manner as if moving under water; then, just before alighting, it rights itself. If you come too near, the sapsucker scrambles around to the rear of the limb, and if you step close up to the tree, the bird starts away in free, sweeping curves, like a skater over the ice, the white in the wing flashing out.
Eaton (1914) notes that “during the migration it is evident that the male birds arrive first, for during 15 years of continuous records which I have kept with this object in view I have found that male birds are the first to be seen each year and no females are seen for several days after the first males arrive.”
Audubon (1842) records the following unique observation:
While travelling I observed that they performed their migration by day, in loose parties or families of six or seven individuals, flying at a great height, and at the intervals between their sailings and the flappings of their wings, emitting their remarkable plaintive cries. When alighting towards sunset, they descended with amazing speed in a tortuous manner, and first settled on the tops of the highest trees, where they remained perfectly silent for awhile, after which they betook themselves to the central parts of the thickest trees, and searched along the trunks for abandoned holes of Squirrels or Woodpeckers, in which they spent the night, several together in the same hole.
A. B. Klugh (1909) reports a remarkably large gathering of sapsuckers on their northward migration. He says:
On the morning of April 17th, 1909, the city of Kingston, Ontario, was alive with yellow-bellied sapsuckers.
From my study window I saw some twenty of them on the trees at the lodge of the park and on going out to investigate I found from one to four on nearly every tree. As a conservative estimate I placed the number of birds in the park at three hundred. * * *
The probable cause of this immense wave of yellow-bellied sapsuckers striking Kingston lies in the strong gale from the north which was blowing on the night of April 16th, the birds apparently dropping as soon as they had crossed the lake.
Courtship.—Little has been recorded on the courtship of the yellow-bellied sapsucker, but we may get a hint of its early stages at least as the birds pass northward—the increased interest in each other shown by their lively pursuits and their rapid whirlings among the branches, as noted under “Spring.”
George Miksch Sutton (1928b) speaks thus of the birds on their nesting ground in Pennsylvania: “In late May and June the mewing cry was familiar and they occasionally indulged in strange courtship antics, flashing through the tops of the trees, calling excitedly in tones resembling those of a flicker, and dancing about with wings and tail spread in a manner utterly foreign to the usually stolid bearing of migrant individuals.”