Appropriateness of size considerations are vital to bird house success. First to attract the right birds and distract the wrong ones. Next to ensure that the parents and nestlings are safe from predators. And finally correct temperature and ventilation.

How elaborate you make your bird house depends on your personal sense of aesthetics. For the most part, all the birds care about is their safety and the right dimensions: box height, depth and floor, diameter of entrance hole, and height of hole above the box floor.

Nesting Box Dimensions

Minimize the Chance of Predator Access

Proper box depth, roof, and entrance hole design will help minimize predator (raccoons, cats, opossums, and red squirrels) access. Sometimes all it takes is an angled roof with a three-inch overhang to discourage mammals.

The entrance hole is the only thing between a predator and a bird house full of nestlings. By itself, the 3/4″ wall isn’t wide enough to keep out the arm of a raccoon or house cat.

Add a predator guard a 3/4 inch thick rectangular wood block, to thicken the wall, and you’ll discourage sparrows, starlings, and cats.

Refer to the above chart, keeping in mind that birds make their own choices, without regard for charts. So don’t be surprised when you find tenants you never expected in a house you intended for someone else.

Ventilation, Temperature and Drainage

Now that you have the correct dimensions for your bird house, take a look at how to make it safe: ventilation, drainage, susceptibly to predators, and ease of maintenance.

Without air vents, boxes can turn into bird ovens. There are two ways to provide ventilation: leave gaps between the roof and sides of the box, or drill 1/4″ holes just below the roof.

Water becomes a problem when it sits in the bottom of a bird house. A roof with sufficient slope and overhang offers some protection. Drilling the entrance hole on an upward slant may also help keep the water out.

Regardless of design, driving rain will get in through the entrance hole. You can assure proper drainage by cutting away the corners of the box floor and by drilling 1/4 inch holes in the box floor. Nest boxes will last longer if the floors are recessed about 1/4 of an inch.

Entrance Hole Sizes

Look for the entrance hole (and exit) hole on the front panel near the top. A rough surface both inside and out makes it easier for the adults to get into the box and, when it’s time, for the nestlings to climb out.

If your box is made of finished wood, add a couple of grooves outside below the hole. Open the front panel and add grooves, cleats, or wire mesh to the inside.

Never put up a bird house with a perch below the entrance hole. Perches offer starlings, house sparrows, and other predators a convenient place to wait for lunch.

Don’t be tempted by those beautiful duplexes or houses that have more than one entrance hole. With the exception of purple martins, cavity-nesting birds prefer not to share a house. While these condos look great in your yard, starlings and house sparrows are the only birds inclined to use them.

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Part of being a responsible bird house landlord is your willingness to look after your wild tenants. If you monitor your bird houses every week and evict unwanted creatures such as house sparrows, starlings, rodents, snakes, and insects, you’ll have much more success in the long run.

For your own safety, please be careful when you inspect those wild bird houses. You may find something other than a bird inside! Don’t be surprised to see squirrels, a mouse, a snake, or a nest of bees or wasps. As for insects, inspect the house for fleas, mites, larvae, and lice on the bottom panel.

If you find insects or parasites try to temper your first reaction to grab the nearest can of insect spray. If you use insect spray use only insecticides known to be safe around birds. An easy check is the label on the can; 1% rotenone powder or pyrethrin spray are known to be safe for wild birds. If wasps persist over time it will help to coat the inside top of the box with bar soap.

Here’s how to check your nesting boxes or bird houses:

Watch the nest for awhile. If you don’t see or hear any birds, go over and tap on the box. If you hear bird sounds, open the top and take a quick peek inside. If everything’s okay, close the box. If you see problems (parasites or predators), remove them and close the box.

This is one time when a bird house with easy access comes in handy! Most bird houses can be opened from the top, the side, the front, or the bottom. Boxes that open from the top and the front provide the easiest access. Opening the box from the top is less likely to disturb nesting birds. On the other hand, it’s absolutely impossible to open a box from the bottom without the nest falling out. Side and front opening boxes are convenient for cleaning and monitoring but they have one major drawback: the nestlings may jump out.

If this happens, don’t panic. Just pick them up and put them back in the nest. Don’t worry that the adults will reject the nestlings if you handle them. That’s an urban legend, old wive’s tale or myth. Most birds have a terrible sense of smell.

If you clean out your nesting box after each brood has fledged, several pairs may use the nest throughout the summer. Many cavity nesting birds will not nest again in a box full of old nesting however so a good cleaning says “We’re open for business!”

In the fall, after you’ve cleaned out your houses for the last time, you can put them in storage or leave them out. Gourds and pottery nests will last longer if you take them in for the winter. You can leave your purple martin houses up, but be sure to plug the entrance holes to discourage starlings and house sparrows habitating the bird house before the martins return.

Leaving your wood and concrete houses out provides shelter for birds during the harsh months as well as flying squirrels.

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Well, perhaps not the only factor, but without considering the placement of the nesting box, you have minimal chance for success.

Where you put your bird house is as important as the design, entrance hole size, materials used, and construction of the box. Cavity nesting birds are very particular about where they live and begin their families. No matter how perfect your nest box, if you don’t have the right habitat, the birds aren’t likely to find it and use it.

Not everyone has the perfect habitat and location for a wood duck, purple martin, or screech owl. On the other hand, just about anyone can attract and entice a robin, titmouse, wren, or chickadee to their yard to rear nestlings.

If you’re reading this artilce I’m going to assume that you have either just built or bought the perfect bird house/nesting box.

But what happens when the birds don’t nest in it? After all it’s been sitting in your yard since February and now months have passed, and not one wild bird has landed on it much less been seen coming in and out of it. What could be wrong?

It may be that you don’t have the right habitat to attract the bird that would love the size and shape of your nesting box, or it may even be as simple as the height you’ve mounted it.

You have a lot of options but I’d always suggest starting with a good field guide or backyard birder’s resource. This will tell you the precise bird your box will suit, the precise bird house you need to attract the birds you’re after, as well as proper placement of the nesting box. You can also learn ways to make your yard more suitable to birds. This really can be as easy as adding a bird bath or planting fruit trees or berry shrubs in your yard.

Of course the easiest is to first identify the birds that are already pleased with your yard and then buy the appropriate nest box.

Should you hang it from a tree limb, nail it to a fence, or mount it on a pole or a tree trunk?

There’s a wide range between how high and low your preferred bird will want their nesting box.

Here are a few tips to get you started:

• bird houses mounted on metal poles are less vulnerable to predators than houses nailed to tree trunks or hung from tree limbs,
• use no more than four small nest boxes for any one species or one large box per acre
• put about 100 yards between bluebird boxes and 75 yards between swallow boxes (if you have both species, “pair” the houses with one bluebird box 25 feet from a swallow box. Put the “pair” 100 yards away.)
• don’t put bird houses near bird feeders
• don’t put more than one box in a tree, unless the tree is extremely large or the boxes are for different species
• if you have very hot summers, face the entrance holes of your boxes north or east to avoid overheating the box.

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Nesting materials can also be hung in a wire cage. These cages are especially popular in the spring when birds will come and choose those that are suitable for them. Try thin strips of clothing or rags, small twigs, wool, and even feathers.

There are more than two dozen birds in the USA and Canada that are happy to nest in bird houses. The most important measurement in any nesting box and the birds it attracts is the diameter of the entrance hole. An inch and a half is small enough to deter starlings. Starlings and house sparrows have been known to kill many baby birds as well as adults sitting on the nest.

Nesting birds have problems with other predators as well. The easiest way to discourage predatory cats, snakes, raccoons, and chipmunks is to mount the nesting box on a metal pole, or pick up a metal predator guard for wood post mounts.

Here are a few of the most common, and preferred, wild birds that you can help in your neighborhood:

Bluebirds – If you put up a bluebird house near an open field, orchard, park, cemetery, or golf course, you’ll have a very good chance of attracting a pair of nesting bluebirds. These beautiful and beneficial birds prefer nest boxes on a tree stump or wooden fence post, elevated to between three and five feet high. Bluebirds will also nest in the old nesting holes of woodpeckers so if a dead or dying tree isn’t posing any troubles and you see a woodpecker hole in the trunk you might like to leave it standing – at least until autumn.

Robins – Robins are our largest birds of the thrush family. They prefer to build their nest in the crotch of a tree or a nesting platform. These birds like to nest six feet or higher up in a shaded area. We get them under the overhang of our hay shed and front porch. Creating “mud puddles” nearby assists robins in the spring, as they use mud to line their nests.

Chickadees, Nuthatches, and Titmice These smaller birds share the same food, feeders, and habitats. If you put a properly designed nest box in a wooded yard, at least one pair is sure to check it out and one may stay to grace you with babies that return year after year! Chickadee nesting boxes are perfect at 6′ elevation. Nuthatches can be between 5-6′ elevation. You can hang them from limbs or secure them to tree trunks. The entrance hole should be 1-1/8″ to attract chickadees yet exclude house sparrows. Encourage these birds to stay in your yard by continuing to fill your suet and peanut feeders through the summer and keep a bird bath or dripper going at all times for them.

Brown Creepers and Prothonotary Warblers – Brown creepers generally like to nest behind the curved bark of tree trunks. If your yard or garden is heavily wooded, slab bark houses will appeal to creepers. Prothonotary warblers also prefer slab bark houses, but they will only nest in boxes positioned over water.

Wrens – Wrens don’t seem to be very picky about where they nest and are a beautiful wild bird to watch rear their young. Try nest boxes with a 1″ x 2″ horizontal slot (larger for the Carolina wren) instead of the standard circle shape entrance as these rectangular openings are easier for the wrens to use. Wrens are notorious for filling up any conceivable nest cavity with twigs, regardless of whether they end up using the nest or not. Since male house wrens build several nests for the female to choose from, hang several nest boxes at eye level on partly sunlit tree limbs. Wrens have always been one of my personal favorites because they are not ‘put off’ by humans being near their homes so they can be poisitioned quite close to the house and are perfect for smaller lots.

Tree and Violet-green Swallows – Beautiful white-bellied birds with iridescent blue-green backs and wing, are a joy to have nearby. They’re also beneficial as they are insect eaters. Tree swallows prefer nest boxes attached to dead trees. Space the boxes seven feet apart, the ideal setting is on the edge of a field near a lake, pond, or river. The gorgeous violet-green swallows from the west, nest in forested mountains. Nesting boxes placed on large trees in a semi-open woodland attracts them.

Barn Swallows and Phoebes – Barn swallows and phoebes are another easy and beneficial bird to attract. It’s their nesting behavior, not their plumage or song, that you’ll fall in love with over and over again. These birds tend to nest where you’d rather not have them: on a ledge right over your front door or at the far entrance to the barn. To avoid a mess by your door, offer the birds a nesting shelf nearby where it’s more convenient and you may get lucky if they prefer it. These birds are not bothered by human activity nearby.

Purple Martins – Many people want martins because, it’s been said, each bird can eat 2,000 mosquitoes a day. While it’s true that Purple Martins eat flying insects, don’t expect purple martins to wipe out your mosquito population. Martins actually prefer dragonflies, which are far more benefical for mosquito control as they prey on mosquito larvae. Don’t cross martins off your list because they don’t live up to their mosquito killing reputation though, these gregarious wild birds from the swallow family put on quite a show for human observers! Martins prefer to nest on the edge of a pond or river, surrounded by a field or lawn. As they nest in groups, the houses you may purchase for a colony are often the most elaborate. Look for a house with a minimum of four large rooms, 6 or more inches on all sides, with a 2 1/2″ entrance hole. You might also like to check out bird house gourds as purple martins seem to prefer these.

Flycatchers – The Great Crested Flycatcher and its western cousin, the Ash-Throated Flycatcher, are common in wooded suburbs. Their natural nesting sites are abandoned woodpecker holes (see note on dead or dying trees above). Flycatchers may nest in a bird house if it’s elevated about ten feet up, in a tree in an orchard, or at the edge of a field or stream.

Woodpeckers – Beautiful and funny wild birds that are easily attracted with suet feeders. However, only the flicker and the red-bellied woodpeckers are likely to use a nesting box to rear their young. These birds prefer a box with roughened interior and a floor covered with a two-inch layer of wood chips or coarse sawdust. Flickers are especially attracted to nest boxes filled with sawdust, which they “excavate” to suit themselves. For best results, place the box in direct sunlight.

Owls – Owls seldom build their own nests. The Great horned Owl and the Long-Eared Owls prefer abandoned crow and hawk nests. Other owls (barred, barn, saw-whet, boreal and screech) will nest in tree cavities and bird houses though. Barn owls are best known for selecting nesting sites near farms. Where trees are sparse, these birds will nest in church steeples, silos, and hay mows. If you live near a farm or a golf course, try fastening a nest box about 15 feet up on a tree trunk to see if you can attract them onto your property (they’re great to keep the rodent population down!). Screech owls prefer abandoned woodpecker holes at the edge of a field or neglected orchard. They will readily take to a nesting box if you line it with an inch or two of wood shavings. If you clean the box out in late spring after the young owls have fledged, you may attract a second tenant–a kestrel. Trees isolated from larger tracts of woods have less chance of squirrels taking over, and often ruining the nesting box.

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Did you know that almost two dozen species of North American wild birds will consider a human-made nesting box? It’s true, but how on earth can you be sure that the bird you want will use your nesting box?

There is only one way and even that way will not guarantee success. After all, birds are wild creatures (as are the animals that harass them) and have minds of their own.

First, learn all you can about the birds you want to attract and offer them an appropriate box. All nesting boxes are not created equal, you want the right size with the right sized opening for your preferred bird. It’s also helpful to you to have one that opens at the top, and the front or side (I’ll tell you why later).

You’ll need to monitor the nest box once you place it in a suitable location (again, birds do have preferences about these things), and you’ll also want to be tough enough to evict starlings and house sparrows. These two are not native North American birds and have done considerable damage to our eco-system so it is wise not to assist them in their breeding habits.

Perhaps one of the biggest responsibilities is ensuring that the boxes don’t become infested with insects. If this happens you’ll want to physically remove the insects and soap the inside top of your nesting box. Of course you can’t do this if you currently have inhabitants. If insects infest the box during nesting, simply apply a light dusting of rotenone or pyrethrin (available at your country supply or home hardware store). Do not use chemical sprays.

Next you’ll have to watch out for the wild predators, namely snakes and climbing rodents. An ounce of prevention is worth a pound of cure – set up physical barriers to these pests to deter them right from the start! You could try inserting a PVC pipe over your metal bird house pole, or add metal sheeting to a wood pole. Smear the PVC or metal with Vaseline laced with hot (cayenne) pepper. Avoid automotive grease, it can be lethal to wildlife. You could also put a predator guard over the nest entrance hole. Finally, do not use bird houses with perches below the entrance hole.

If you find other bird species attacking the nesting adults, eggs or nestlings, you’ll have to take a different action dependant on the attackers. Eliminate house sparrows and starlings. All other birds are protected by federal and state laws such as hawks, owls, falcons, crows, grackles, jays and shrikes.

Finally, when your babes have flown the coop (so to speak) remove and thoroughly clean the nesting, soap up the lid again and replace for the next season.

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The chapter I’m on now is discussing nesting box success (dimensions, placement and predator prevention), but the fact that escaped me on the first read, and that shocked me the most is this:

“Everyone engaging their lives with the lives of birds should understand that 90 percent of the birds born in any given year fail to see the next. Nest failure is the first major cut on the way to maintaining the population at a healthy level that does not outstrip resources.”

You see 90% of the birds born this year won’t make it to the next year and nest failure is the biggest reason for the mortality rate.

90%!

Nest failure takes the most, with these secondary causes: natural predators, starvation, hypothermia and insect infestation (these ‘killers’ can be kept at bay with your intervention as well – all with correctly placed and maintained bird houses).

Those numbers are shocking, but I don’t doubt Pete Dunne for a moment. As Vice-President of the New Jersey Audobon Socieity and the director of the Cape May Bird Observatory, I’m sure he has his numbers right.

With all the adversity our wild birds have to cope with in North America I think the more we can help our wild birds, the better.

Providing, maintaining and protecting nesting boxes is one huge step in the right direction and it serves us as well. More birds in our backyards and gardens means less bugs and insects. It’s fun and rewarding to know that we helped a few birds get their start – many of which (if all goes well) will return to our property the following year.

Now is the time, in fact it may even be a little late for the first clutch of some species.

• With the return of spring and warmer weather most wild birds have already scouted out their nesting selection, if you’ve got boxes get them cleaned or re-hung.
• If you don’t have nesting boxes you can buy some really cheap (here’s a $10 off coupon – use promo code: SW-8937 in the category Bird Houses).
  Even if the birds don’t arrive on your doorstep for a few weeks you are still helping. Many birds will have two or more clutches per season and may be looking for a more suitable spot than they had on round one.

I thank you all, who happen upon these pages, and who make a concerted effort to assist our backyard birds, both at the feeding stations and with their nesting needs.

Veronica

p.s. Here is the Pete Dunne book that I reference above, just for your info. If you don’t have this, but love birds, you’ll enjoy this book for years to come.

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