With bluebird nesting box cleanup and placement time upon us, I thought I’d discuss them and the other cavity nesting birds. The Eastern Bluebird, and the Western and Mountain bluebirds in fact, are the only cavity nesting thrushes.

When Pennsylvania, “Penn’s Woods,” was beginning to be settled, the first pioneering Pennsylvanians found the state almost completely forested. I can conjecture that the many beavers found in the state had flooded many small streams and killed off the trees there. These dams sometimes broke in floodwaters and what remained were the few grassy areas to be found. Bluebirds then were not as common as today with only these smaller meadow-like areas to feed and nest. Once Pennsylvania became more of an agricultural state, the bluebird populations increased, until starlings were introduced to New York City, with their rapid spread and bully-like dispositions, the bluebird numbers dropped. Thankfully, the popular bluebirds got help from nest box builders and the bluebird trails they established and they rebounded. We learned that a simple trick of making the entrance holes only 1½ inches in diameter, excluded these European imports.

We do have a few forest dwelling birds that nest in cavities too. Fortunately for them we have a number of woodpecker species that create most of these cavities. Downy, hairy, red-bellied, and pileated woodpeckers as well as northern flickers excavate a new nesting cavity each year. They seldom use the same cavity again.

These woodpecker nesting sites, and the occasional natural openings, offer great places for the following birds to nest: tufted titmouse, black-capped chickadee, white-breasted nuthatch, red-breasted nuthatch, and even one flycatcher species, the great crested flycatcher. Tree swallows that traditionally nest near or along water sources use the vacated woodpecker holes also

Pileated woodpeckers, which in my lifetime have been increasing in numbers, are particularly helpful. Their much larger and oblong shaped handiworks are of course used by the above-mentioned songbirds but one other larger bird really appreciates the larger cavity, the eastern screech owl. The screech owl needs an opening three inches in diameter or larger to nest

Of course, I listed the songbirds that are cavity nesters but all of our woodpecker species obviously nest in cavities. The strictly nocturnal flying squirrels will use the pileated woodpecker holes to hide in during the day, and when it is time for breeding, will raise their young there too. In suitable habitat, such as a fence row or field edge, American Kestrels will gladly use the abandoned pileated woodpecker holes. They, like the screech owl, need an opening greater than three inches.

Finally, before everyone started building or erecting bird houses, the house wrens used natural and woodpecker made cavities for their nest sites. But remember they are most likely found closer to humans, and not the larger forested areas of northern Carbon and Monroe counties.

Note: Now is the time for bluebirds to claim nesting sites. If building or buying boxes, make sure there is no perch, a 1½ inch opening, the cavity should be about 8 inches deep and have about a 4½ inch inside box dimension. Ideally, place them in the open, facing southeast, preferably on a galvanized pipe and about 5 feet from the ground. Use sources gleaned from websites for dimensions and specs for placing nesting boxes for the other songbirds I mentioned in this column. Enjoy those birds, they’ll be arriving in droves over the next 6 to 8 weeks.

Test Your Outdoor Knowledge: After being introduced to New York City’s Central Park in 1890, how long did it take starlings until they spread across America to the West Coast? A. 10 years; B. 30 years; C. 80 years; D. 125 years.

Last Week’s Trivia Answer: It is a fallacy that “whitetail” bucks lose their antlers because of extremely cold temperatures. Deer age, nutrition, and hormone levels all are factors. I have trail cam pictures of bucks as of March 5 still sporting both antlers although some have only one left attached.

Email Barry Reed at breed71@gmail.com.