It is well known that during the winter eastern bluebirds sometimes roost together in the same cavity or nesting box. Although much is yet to be learned about this behavior, observations of bluebirds roosting in a nest box in Indiana during a period of extremely cold weather provide us with insight into the fascinating roosting habits of this popular bird. The event I am describing here took place in Indiana during a period of extremely cold weather.
Throughout this spell of frigid weather, as many as 14 bluebirds used a single nesting box as their nighttime roost. It is interesting to note that while a number of other apparently suitable boxes stood nearby, all of these birds used the same box night after night.
The roosting birds did not simply pile atop one another after they entered the box. To the contrary, they carefully arranged themselves in two to three layers. The birds comprising each layer positioned themselves so they looked like spikes on a wagon wheel. Once each bird settled in, it faced toward the outside of the box.
Birds arranged in such a manner would have little chance of suffocating during the night. By so doing, the warm air expelled by each bird would also help keep the interior of the nesting box warm.
Since the weather has abruptly changed from being more like autumn than summer, my wife and I have been seeing eastern bluebirds inspecting some of our nesting boxes. I am certain the birds are not checking out potential nesting sites–it is much too early for that. The birds may be just curious, or perhaps the onset of cold nights has triggered a search for suitable roost sites.
In addition to the bluebird, a number of familiar backyard birds also roost in cavities and nesting boxes including screech owls, woodpeckers, tufted titmice, brown-headed nuthatches, and Carolina chickadees. In the case of the bluebird, they typically roost alone in warm weather. However, when temperatures dip below freezing, a cavity or nesting box might harbor anywhere from a couple to more than 20 bluebirds.
The advantage of nesting together is the birds share their body heat. During an extremely frigid night, the additional heat offered by a group of roosting birds may spell the difference between life and death.
With that in mind, as we enter the harshest portion of the year, keep an eye on your nest boxes. There is a good chance one more bluebirds or other cavity-nesting birds are roosting in a box erected to provide a place for them to nest.
The best times to look for such activity is late in the afternoon when the birds are going to roost, or first thing in the morning when they are leaving for a day of foraging.
You can also peek inside a box. If you see some downy feathers scattered about the bottom of a box, chances are birds are roosting there.
Although the Carolina wren is considered to be a cavity nesting bird I must confess I have never found a Carolina wren nest in a natural cavity or nesting box. In fact, when it comes to Carolina wren nests, I have learned to expect the unexpected.
I have found Carolina wrens nesting in my well house, beneath the cover of a propane tank as well as in a cardboard box sitting on a shelf in my garage. Others have discovered Carolina wren nests is strange places too.
For example, their nests have been located among the rocks of stonewalls, clothespin bags, hanging baskets, open paper bags, mailboxes, buckets, as well as in old hats and shoes.
One year Carolina wrens nesting in North Carolina chose as their nesting site a Jeep Wrangler. They constructed their nest where a shock absorber was attached to the frame of the vehicle. What makes this nesting so fascinating is the fact the vehicle made three trips before the nest was discovered.
Carolina wrens apparently have no problem nesting in vehicles that are driven about. Decades before the famous Georgia ornithologist, Thomas Burleigh reported that, in 1928, a pair of Carolina wrens nesting in Athens chose as their nesting site a touring car. The vehicle was left near a sawmill for two days. During this time, the wrens began building their nest beneath the hood of the car. When the car was driven away and returned the next morning, the unperturbed birds resumed construction of their nest.
If you have never located a Carolina wren nest on your property, perhaps you have been looking in the wrong places. This year focus your search on places you would never expect a self-respecting wren to nest and you just might find the nest that has been eluding you for so long.
I would venture to say most people would not think of putting up a bird box in November. However, if you stop and think about it, it is the perfect time to take on this labor of love.
This is a great idea because cavity nesting birds such as eastern bluebirds, Carolina chickadees, tufted titmice and the like use tree cavities and nest boxes for roosting and nesting. Consequently, by erecting a box at this time of the year you box will serve as a winter roosting site and be available for nesting next spring.
There are rarely enough winter roost sites available for the birds that use them. Take eastern bluebirds, for example. At this time of the year, your neighborhood can serve as the winter home for adult bluebirds that nested this year, their young and migrants from points north.
The ability of cavity nesting birds to find a winter roost site prior to a frigid winter night can be critical to their survival. Those that cannot locate such cover stand the chance of freezing to death before morning.
If you are going to erect a new box, here are a few things you can do to make it a bit cozier for winter occupants. First, place an inch or so of dry wood chips or dry grass in the bottom of the box.
Some folks even go to the trouble of covering the bottom of the box with a piece of Styrofoam. If you do so, bore a few holes in the Styrofoam for water to drain out of the box.
Another modification you might consider is plugging the box’s vent holes this prevents warm air from escaping the box. If you add a piece of Styrofoam and/or plug the vent holes, remove the insulation before spring.
You can also drill a couple of holes on either side of the box. A wooden dowel can be inserted through the holes. By so doing, you are providing roosting birds with a perch. At the end of the winter, the dowel can be removed before nesting season. Since upwards of 20 or more birds will sometimes roost in a bluebird nesting box on a cold night, the dowel will make it more comfortable for the birds escaping the cold.
If you are curious as to whether or not your box is being used as a winter roost site, simply inspect it for signs of use. If birds are roosting there, they often leave behind feathers, droppings, and sometimes food.
A word of caution: do not check a box at night. Birds disrupted during the night will often stop using the box from then on.
Finally, before putting up a box, place a metal hole guard around the entrance hole. This prevents squirrels from enlarging the hole and ruining the box.
Over the years, I have encountered eastern bluebirds nesting in a variety of locations, however, recently I was shown a bluebird nesting site like no other. Beyond a shadow of a doubt, it is the most colorful and unique nesting location I have ever come across.
This nesting box is situated in a forest of trees. This is not a forest of pines or hardwoods; this forest is composed of a kaleidoscope of more than 140 bottle trees. Dr. Jerry Payne, the creator of this fanciful forest, has dedicated one of his beautiful creations to the eastern bluebird. Bluebirds must have found this special tree as pleasing to their eyes as we do. During each of the three years the box has hung on a bottle tree nestled between an array of colorful bottles, bluebirds have successfully fledged young.
If you have encountered an unusual bluebird nesting site, I would like to hear about it.
It seems like everyone wants a pair of bluebirds to nest in their yard.Consequently, it is not surprising that far more bluebird nesting boxes are sold across the country than those designed to attract other cavity nesting birds.However, for many, whether or not bluebirds will use a box is often a hit and miss proposition.If you are one of those folks that have not been fortunate enough to have bluebirds use a box you provided for them, it might be because bluebirds may not consider your yard to be prime breeding habitat.
In the world of the bluebird, the male selects the breeding territory and the female picks the place where she will nest.In Georgia, male bluebirds may begin scouting for spots to stake a claim on a breeding territory as early as February.These territories can range anywhere from two to twenty-five acres in size.
If a male bluebird decides that your yard is part of his nesting territory, you are half way home.Nesting will not take place until the female also agrees with his choice.Part of this process takes the form of the male carrying nesting material into and out of each potential nesting cavity in the breeding territory. After the female inspects all of the sites, she may actually build her nest in a number of cavities before making a final decision and begin laying eggs.
The eastern bluebird will not nest just anywhere.When it comes to backyards, they prefer those that are open and park like. If trees and shrubs are present, they should be scattered and interspersed with low-growing vegetation.
The male is looking for an area that contains at least one potential nesting site.These can be abandoned woodpecker holes, cavities in wood posts, hollows in trees or nesting boxes.Some territories harbor numerous nesting sites.
In suburban/urban landscapes, bluebirds seek areas that feature open lawns and suitable nearby perches.The perches are used for a variety of purposes such as hunting, defending a breeding territory, from other bluebirds, as well as spotting approaching danger.
Bluebirds prefer to hunt for insects and other prey on or near the ground within a twenty-foot radius of their perch.As such, your yard should have several perches.Power lines and tree limbs serve as ideal perches.With that in mind, trees pruned so that there are no leaves and branches within eight to ten feet of the ground.
Also, the quality of the feeding habitat can be greatly enhanced if a weedy border is maintained around the perimeter of a yard.These areas harbor far more food than vast expanses of manicured lawn.
Water is also a critical component of a bluebird’s breeding territory.If a stream or pond is not nearby, install and maintain a birdbath.When selecting a bath, choose one that is an inch to an inch and a half deep.Such baths are used for both drinking and bathing.
If this description of ideal backyard bluebird breeding habitat does not describe your yard, do not despair; other cavity nesting birds need places to nest too.My recommendation is to go ahead, put up a box, and see what happens.It is possible that another bird such as a brown-headed nuthatch, tufted titmouse, Carolina wren, or Carolina chickadee will find your backyard to be perfect for its needs.
If you erect bird nesting boxes, invariably there will come a time when a woodpecker, gray, or flying squirrel takes it upon itself to enlarge the entrance hole on one of your bird boxes.When this happens the perpetrator might enlarge a 1.5-inch entrance hole to one that is now is 3-4 inches in diameter.
Whenever a bird or mammal remodels the entrance hole in a nesting box, the structure is often destroyed or, at the very least, puts any bird that tries to nest in the box at risk.
A bigger hole allows larger birds to nest in the box.Most boxes erected in Georgia are designed to help alleviate the eastern bluebird’s housing shortage.A box equipped with a 1.5-inch hole, prevents larger, more aggressive European starlings from nesting in the box.Without such protection, bluebird numbers would plummet.
A larger hole also allows nest predators such domestic cats, raccoons, and even opossums to reach into a box and snatch out nesting adults, their eggs, and young.
I have found that one of the best ways thwart unsolicited attempts to alter the size of entrance holes is to equip nesting boxes with a simple, inexpensive device called a hole guard.
The hole guard is nothing more than a piece of metal that is attached around the entrance to a nest box.They are available in various sizes.For example, if you want to encourage birds the size of a bluebird or smaller, install a hole guard featuring a 1.5-inch opening.Likewise, if your goal is to encourage smaller birds, such as Carolina chickadees to nest in your boxes cut a one-inch entrance hole in your box and protect it with a one-inch hole guard.
Believe me these simple devices work. In fact, they are so effective, I will not erect a new box without one.
In all the years that I have used them, I have seen a hole guard fail only once.In that case, the hole guard actually worked, however, an unknown critter almost totally destroyed the entire box. In spite of this all out attack, the hole guard remained in place.
Hole guards can be purchased are stores that specialize in birds. If you try one, you will not be disappointed.
A number of backyard birds nest in tree cavities. The list of these birds includes the eastern bluebird, tufted titmouse, Carolina chickadee, great crested flycatcher, screech owl, brown-headed and white breasted nuthatches, purple martin, tree swallow, Carolina and house wrens.
The problem is there are rarely enough natural cavities to go around. In addition, the suitable cavities that do exist are often taken over by aggressive introduced species such as house sparrows and European starlings. As a result, often few, if any, native cavity-nesting birds nest in Georgia’s backyards and neighborhoods.
Fortunately, many cavity-nesting species will nest in nesting boxes, Consequently, by erecting one or more nesting boxes in your yard, you will help alleviate this severe housing shortage and increase the diversity of birds using your yard.