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A male bluebird parent with his begging male offspring during feeding. Photo by Vickie Henderson.
Text and Photos by Vickie Henderson
The Eastern Bluebird needs little introduction for this species is not only one of the most celebrated birds known to humankind because of its color and song, but also the subject of one of the most heart-warming conservation stories in our nation’s history—the establishment of the “Blue Bird Trails” movement. This widespread grassroots effort that spread throughout the country in 1934 is attributed with saving the species by replacing disappearing natural nesting cavities with human-made nestboxes.
A brightly colored thrush species that prefers open, short cropped lawns and fields adjacent to woodlands, the bluebird is a secondary cavity nester, meaning they cannot excavate their own nest cavity but must rely on nesting holes abandoned by other species. These specific habitat requirements made the bluebird highly vulnerable to changes in farming practices, and the proliferation of exotic species, especially the European House Sparrow and European Starling that compete for natural nesting cavities.
The bluebird’s vulnerability, however, extends beyond the breeding season. Year-round residents of Tennessee, bluebirds use up their fat stores rapidly, within a day or so, and must replenish body fat with food in order to withstand extended periods of ice, snow and cold. This became evident in the winters of 1976-1977 and 1977-1978 when thousands of bluebirds died throughout their winter range due to extreme freezing temperatures and lack of food. The fortunate part of this story is that the bluebird population bounced back in a short period of time and human intervention can help during these unpredictable harsh times.
Besides its beautiful blue and rust colors and delightful warbling song, the bluebird has a companionable nature and readily tolerates human presence making ideal conditions for observation and enjoyment. The requirements for attracting bluebirds include the basics—food, shelter, and water—but the key and central ingredient is the nestbox. Because Tennessee has a moderate winter climate our bluebirds do not migrate, but remain with us all winter long, making the nestbox a central attraction throughout the changing seasons.
During fall and winter months, bluebirds check out nest boxes for cold weather shelter and future nesting sites and continue to examine nesting cavities throughout the non-breeding season. The breeding season begins early March and lasts through July and August in Tennessee. This means anytime is the right time to add a nest box to your backyard habitat.
The nesting box should be placed in an area of sparse vegetation with nearby tree limbs for perches and a clear flight path to the nestbox entrance. Bluebirds hunt from perches above ground and drop down to the ground to capture their prey which includes grasshoppers, crickets, beetles, caterpillars, grubs and spiders—prey that is most easily spotted in low vegetation. In winter months their diet is supplemented with wild fruit and berries, such as dogwood, holly, honeysuckle, poke berries and sumac.
Billie Cantwell, the current president of the Knoxville Chapter of the Tennessee Ornithological Society and an enthusiastic “bluebirder,” assisted me at Knoxville’s Wild Birds Unlimited in 2011 when I purchased my mealworm feeder and suggested I put mealworms out at a regular time each day and whistle. “The bluebirds will catch on,” she said. Being less than enthusiastic about handling mealworms and a historic failure at whistling, I listened doubtfully.
It wasn’t long before all hesitation evaporated as I witnessed a bluebird’s response to a dish of mealworms. One of my nesting females, in particular, chirped enthusiastically each time she encountered a dish of mealworms and would fly to me and land on a nearby perch wing-waving to solicit mealworms for an empty dish. Wing-waving is a series of alternating wing lifts used frequently by bluebirds in communication with mates and seems to convey greeting and encouragement. To be favored with such intimate communication from a bluebird is indeed an honor and a privilege.
Bluebirds have keen eyesight and their dedication to feeding their young makes them highly motivated to take advantage of an easy food source. To an unfamiliar bluebird, the mealworm feeder is a neutral addition to the landscape and the guard around the feeding dish can present a puzzle initially. By offering a dish of mealworms on the ground within full view and scattering a few mealworms on top of the feeder, bluebirds readily learn to navigate the feeder guard that is designed to keep larger birds out.
In the winter months, I supplement the mealworms with homemade peanut butter suet that provides a source of fat and protein during cold winter periods. Bluebirds do not readily recognize suet as food, but when crumbled and served in the same dish with mealworms, they pick up small amounts, discover they like it, and eat it from that point forward. This increases their likelihood of getting the fat and protein needed to replenish fat stores during harsh winter conditions.
During the nesting season only mealworms are fed and the mealworm feeder becomes a central place of activity. While bluebirds feed their young a variety of insects and spiders, they will also feed generous amounts of mealworms to supplement these feedings. After fledging, juveniles perch near the feeder to be fed and by watching their parents, learn to navigate the feeder guard and feed themselves.
You can find nest boxes and mealworm feeders at your local bird feed supply stores and at online sources. There are many designs for bluebird nestboxes and varying opinions about the best designs. The Frank Zuern Horizontal Bluebird House has come into favor recently. This horizontal design simulates a hollow tree branch, a widely used natural cavity for bluebird nesting, and offers protection against reaching predators, as well as, good ventilation for cold winter nights when dozens of wintering bluebirds may roost huddled together to sustain warmth during extreme cold.
Additionally, a predator guard is a must. The predator guard on my nestbox was designed by KTOS member, Colin Leonard, made from sturdy hardware cloth, and based on a raccoon’s arm length that is approximately nine inches. It has also been effective at deterring the reach of free-ranging cats and may deter snakes. I have had no loss due to predation in two seasons of four nest broods using this predator guard.
During the 2012 breeding season, while my bluebird pair were raising their second brood of five, just four days before the nestlings were due to fledge, the female disappeared. On the second day of her absence, the male was observed flying to the mealworm feeder in the company of his first brood male off-spring, wing-waving and chattering. The juvenile responded by feeding on mealworms. He then carried mealworms to the nestbox and fed the nestlings. In the days that followed, all three juvenile off-spring assisted the adult male in the care and feeding of the nestlings—protecting the nest area from intruders, bringing a variety of foods to the nestlings and removing fecal sacs from the nestbox.
The juveniles followed the male’s cues during the hours before the nestlings fledged, a quiet time that is punctuated by brief periods of soft contact calls that echo from the nest box and resound throughout the yard as the family practices calls that will help locate the nestlings after they fledge. These are the intimate observations that tug at the heartstrings.
In their need for human intervention to offset changes in their world, bluebirds invite us to enter their lives and become part of it. Accepting that offer is a decision that will not only brighten your life, it will forever deepen and enrich your appreciation of the natural world.
Here are some books and resources you may refer to for more information: Studying Eastern Bluebirds, A Biologist’s Report and Reflections by T. David Pitts, self published in 2011, ISBN 0615411339; or Bluebird Book, The Complete Guide to Attracting Bluebirds by Donald and Lillian Stokes, 1991, ISBN 0316817457.
For the Leonard Nestbox Predator Guard: visit the Web site: http://vickiehenderson.blogspot.com/p/bluebird-nest-box-predator-guard.html.
A peanut butter suet recipe can be found on the website: www.vickiehenderson.blogspot.com/p/bird-suet-recipee-loved-by-bluebirds.html.
Videos of juvenile bluebirds feeding nestlings on the website: www.vickiehenderson.blogspot.com/search/label/bluebird%20family.
For the Frank Zuern Horizontal Bluebird House, visit the website: www.savingbirds.org/PDFs/BlueBirdHouse.pdf.
(Vickie Henderson is an artist, writer and photographer residing in Knoxville. She is author and illustrator of Red-shouldered Hawk Territory, A Sketchbook Journey Through Nesting Season; the Tennessee Ornithological Society’s Discover Birds Activity Book; and Operation Migration’s Whooping Crane Activity Book. Visit her blog site: www.vickiehenderson.blogspot.com/.)