From our Naturalist, Rosetta
This is a great time of year to hike the trails through the Flat Rock Brook forest. From now until the trees leaf out, there is much to see: several species of over-wintering birds can be found, and they’ll soon be joined by their migratory counterparts. But if you miss them, it’s easy to find signs that birds and other wildlife have been in the forest: just look at the trees – on the trunks are scratches, scars and patches that have been denuded of bark. Holes of all shapes and sizes are in the trunks and branches. Many of the holes were made by woodpeckers. I’m not going to attempt to identify which species has excavated each hole, but on your next hike, maybe you can determine which woodpecker has left its mark.
Four woodpecker species are year-round residents at Flat Rock Brook: the downy, hairy, and red-bellied woodpeckers are daily visitors to our feeders and the pileated woodpecker can be found in the forest. All four species breed here. The yellow-bellied sapsucker doesn’t breed this far south, but the species leaves plenty of evidence that it overwinters here, or at least passes through. And although the Northern flicker is a year-round resident in New Jersey, we don’t usually see them until spring arrives.
Pileated woodpeckers, the largest woodpecker species in North America, are master excavators with huge chisel-shaped beaks. They forage in standing dead trees, stumps, or logs lying on the forest floor, digging rectangular-shaped holes that can be a foot or more long. These are among the most easily identified holes along our trails. The entrance hole to the pileated woodpecker’s nest is somewhat oblong to roughly triangular rather than the circular shape of most woodpecker holes. They are roughly 3 1/2” across and typically found on the main trunk of a dead tree, 15-70’ above the ground.
Smaller birds make smaller holes. The nest hole of a hairy woodpecker is typically 1 ½ - 2” wide. The entrances to their nests are just large enough for them to fit through. They excavate in dead trees or dead branches, often placing the entrance to the nest on the underside of a branch or anywhere from 4 to 60‘ above the ground. They make smaller holes when foraging, too: they tear off bark and drill holes no more than ½”, making a wavy pattern as they weave back and forth on a trunk in search of insects.
Red-bellied woodpeckers drill nest holes about 2” wide, placed 12-20’ high. They also peck into trees as they forage.
The smallest woodpecker in North America, the downy woodpecker, drills an entrance hole about 1 ½” wide 12-30’ above the ground. They typically place the entrance hole on the underside of a dead branch or stub, often in wood that is infected with a fungus, making it soft and easy to excavate. Downy woodpeckers do not drill holes as they forage, instead they probe for insects along thin branches and stems of reeds.
Northern flickers generally excavate nest holes 6-20’ off the ground, but they can be as high as 100’. The entrance is of about 3” diameter. They will often reuse cavities that they or another species excavated in a previous year. The northern flicker is the only woodpecker that regularly probes along the ground for ants and other yummy food items.
Although the yellow-bellied sapsucker does not nest in New Jersey, there is ample evidence that it lives in the Flat Rock Brook forest during the winter. Not usually a visitor to our bird feeders, the sapsucker makes neat rows of round or squarish pea-sized holes in live trees to harvest sap. The holes are nearly always in a horizontal line, and they will drill more than one line of holes in a tree. Tree sap collects in these holes and sapsuckers lap it up with their tongues. Insects are attracted to and get stuck in the sap, providing a protein-rich meal to the birds.
By excavating dead wood as they do, woodpeckers provide important services to the forest and other living creatures. They control insect populations and speed up the process of forest decay and nutrient recycling, which provides foraging substrate to other species. The holes woodpeckers make for nesting can be used year after year, but they aren't always used by woodpeckers. Abandoned woodpecker nests provide nesting and shelter to other cavity-nesting birds such as wrens, chickadees, nuthatches, and bluebirds, or to mammals, such as flying squirrels.
Even humans are part of this cycle. By leaving dead trees, called snags, standing and not trimming dead branches, we provide the substrates for our resident woodpeckers to make their homes. As long as a dead tree or branch does not pose danger to our human visitors it is left standing. So too, are the dead trees and branches left on the forest floor, because you never know what will be foraging or living in them. And as they break down, their nutrients are returned to the soil to provide new growth and habitat.
