With bluebirds now nesting across the state, I am often asked, “Should I check my bluebird boxes?” When this question is posed I always tell folks that, if it done properly, checking bluebird nesting boxes can actually be beneficial to the birds. Let me explain.
Unlike many birds, the eastern bluebird is more tolerant of human activity around their nests than many other birds. This tolerance allows the close monitoring of the success of the birds’ nesting efforts. By so doing we can help thwart situations that can lead to the failure of a nesting attempt.
For example, we can keep house sparrows from taking over a box by tossing out the sparrow’s bulky nesting materials. If this is done enough times, the aggressive, unprotected, invasive house sparrows will finally give up and leave the box alone.
(Never remove the nest of a native cavity-nesting bird.)
Also, wasps will occasionally attempt to build a nest on the underside of the top of a box. If wasps are allowed to build a nest inside a box, bluebirds will abandon it. With that in mind, if you find a small wasp nest, remove it.
If you plan to monitor a box, make sure the box can be easily opened. Too often boxes are made in such a way that the box cannot be opened from the top or side.
Make every effort to make nest box checks as brief as possible. In addition, it is always best to check boxes when temperatures are mild, winds are calm, and it is not raining.
Checks can be safely performed weekly up until the hatchlings are 12 or 13 days old. Checks made after that time can result in the youngsters prematurely bailing out of their nests.
If you monitor you boxes on a weekly basis, you will know when a nest is built, when a female lays all of her eggs (females lay one egg a day until the clutch is complete), incubation has begun, the approximate age of the hatchlings, and how many young bluebirds successfully fledge.
Here are some facts that will help you understand what you will be observing. Typical clutch size is 4-5 eggs; Incubation lasts 12-14 days; Time of fledging: anywhere from 17-21 days.
The North American Bluebird Society recommends the nest be removed after the young fledge. If a bluebird wants to use the box later, a new nest will be constructed in short order.
However, dispose of the old nesting materials some distance from the nest site. This will help keep potential predators from discovering the location of the nest.
Keep in mind, eastern bluebirds will nest up the three times a year.
If you have additional questions about checking, please let me know.
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.
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.
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.