Partnership That Works
tiny holes drilled by this Yellow-bellied Sapsucker are an important
source of sweet fluid for Ruby-throated Hummingbirds in early spring
the only ones who love sweet syrup! Yellow-bellied Sapsuckers time their
migration to return north right when sap is running. These special woodpeckers
tap little holes in a circle around the trunk or a higher limb. Then they
come back over and over again to lap up the sap with their brushy tongues
and to pick up insects that are drawn to the sweet liquid.
Eventually the trees make "scabs," closing off the holes. So
the sapsuckers make another ring of holes right above or below the first
ring. They might choose maple syrup if healthy maple trees didn't have
such hard wood. Instead, they tap the sap in softer trees, especially
The Sapsucker Connection
other birds love sap and the insects that collect near it, but most don't
have the beaks to get at it. Sapsucker holes are an important food source
for at least 35 species of birds.
Sapsuckers winter in the southern United States. They are one of the first
migrants to appear in northern states and provinces in early spring —
right when sap is running strong. They migrate about two or three weeks
before hummingbirds do. They often rest for a week or two in spots between
their winter and summer homes. As they do, they make temporary feeding
stations. Sapsuckers spend much of their time drilling holes, usually
going back and forth working on two or three different tree branches at
a time. One migrating sapsucker drilled 286 tiny holes in a pine tree
in 9 1/2 hours one April day, providing a bounty of food for itself —
and for other birds!
While sapsuckers are guarding and feeding at one set of
holes, a host of other birds may visit their other sets of hole in search
of sap and insects. Sapsuckers only drill holes during the spring and
summer while sap is running. As sap dwindles, the sapsuckers turn to flying
insects, ants, fruits, and nuts for food.
Hummingbirds in Pursuit
first Ruby-throated Hummingbirds to return north in the spring, usually
when weather is still cold, often depend on sapsucker holes for their
food. Once enough flowers bloom, they no longer need to "get by with
a little help from their friends."
Ruby-throated Hummingbirds have been seen actually following
sapsuckers as these woodpeckers visit their sap trees. Do you think this
may help the hummingbirds learn the location of these trees? As long ago
as 1891, a scientist named Frank Bolles noticed that hummingbirds visit
sapsucker holes more than any other birds. He saw them come to these holes
throughout the summer, but especially in early spring. Experts who have
analyzed sap say it is remarkably like flower nectar. Both contain sucrose
and traces of amino acids. So sap is a perfect substitute for nectar in
areas where few nectar-rich flowers are blooming and where sapsuckers
When two species associate closely with one another, benefiting at least
one without harming either, the relationship is called symbiosis.
Hummingbirds get an obvious food benefit from sapsuckers, but sapsuckers
may also get help from the hummers.
Hummers Return the Favor
In northern Wisconsin one May, ornithologist Laura Erickson spent many
hours studying some sapsucker trees. The woodpecker had drilled circles
of holes in three different aspen branches for feeding. While the sapsucker
fed or rested on one branch, Laura watched other birds
— Ruby-crowned Kinglets, Cape May Warblers,
Yellow-rumped Warblers and Eastern Phoebes
— come to the holes in the other two branches.
Most of the time, two or three birds gorged themselves at each feeding
spot. But whenever a hummingbird visited, it pugnaciously chased away
any birds that happened to be there
— except the sapsucker. While hummingbirds
eat a lot of food compared to their body weight, they don't eat much compared
to warblers and phoebes. Therefore, hummingbirds may be helping sapsuckers
by defending the sapsucker's hole borings from other larger, hungrier
species. It may be a partnership that works both ways!
binoculars, look very carefully at the top branch tips of different
kinds of trees. Do you see any with tiny insects swarming at the newly
running sap? Can you find any birds up there?