Community column: His dedication branches out from bluebird boxes

Carl Hansen’s rounds start this month, with pre-season box checking. Photo by Catherine Van Noy

For 40 years, Carl Hansen conducted genetic research with the National Institutes of Health. Retired and living in Radford, Dr. Hansen continues his investigative ways, but in a completely different lab. What began as a simple volunteer gig has generated five years of nesting data on bluebird and other cavity dwellers in the New River Valley.

Hansen’s introduction to his current experiment occurred at a Pathways for Radford meeting. A call for help to check bluebird houses in Bisset Park seemed like a good way to spend time outdoors and help the community. But the scientist could not be suppressed. “After about two or three weeks, I began to dimly realize that there was something more than counting birds here,” Hansen recalls. “I was really interested in the patterns.”

Four species dominate the nesting boxes along the Riverway Trail in Bisset Park — bluebirds, tree swallows, house wrens, and chickadees. The same goes for the houses Hansen now tends at nine other locations. He began with 17 boxes in 2006. In 2011, he monitored 276 and is adding two new trails this spring. Monitoring involves visiting the sites weekly and recording his findings: species nesting, eggs present, number of nestlings, next clutch, and so on. Activity runs from March 15 for 26 weeks. The collective number of data points is astounding: over 7,000 for this past year.

And it’s the statistics that keep Hansen going. Once a month, he “downloads” the information collected — in a small field notebook carried on his daily jaunts — to an Access database. When the season is over, Hansen crunches the data, pouring his notes into Excel spreadsheets that graphically reveal how these four species interact, their waxing and waning, high points and low points from week to week, and year to year.

For example, according to Hansen’s charts, Radford’s Riverview Park has a high occupancy rate of tree swallows for most of the summer season. In Pulaski County’s Randolph Park, house wrens dominate the early spring months. At Childress 1 (our farm), chickadees rule the day in April, followed by house wrens. Bluebird fledgling peak for all trails is around Week 12, at mid-June.

Hansen’s data also reveals an interesting, and possibly distressing, pattern with the bluebird population in Bisset Park. Something happened in the summer of 2007 after which egg and hatchling counts have dropped each year.

Chickadees should be the first visitors to most nesting boxes in the area Carl Hansen tracks. Photo courtesy of Bob Abraham

Such findings can be discouraging; Hansen’s interest persists. Through rain and other natural hazards, he is dedicated to keeping the project going. “Finding a snake in the box tends to wake one up,” he admits. His rounds start this month, with pre-season box checking, repair if needed, to make sure all is set for the first visitors, which, according to his records, should be chickadees at most locations.

Hansen will present his findings during today’s Radford’s Fifth Annual Roosting Festival. The birding extravaganza hatched as a celebration of the local vulture population, but has evolved into a well-rounded feting of feathered friends.

A bird walk at 9 a.m. led by Clyde Kessler starts at the Sundell/Park Road entrance to Wildwood Park. Hansen’s talk along with presentations by the Virginia Wildlife Center and a local raptor rehabilitation team run at the McHarg School from 1 to 5 p.m. Kids will love the crafts and other surprises, such as the giant bird’s nest. Find a complete schedule of events here.

By Catherine Van Noy
Special to The Burgs | 639-3330

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