Gilbertson FAQs

Here are common Frequently Asked Questions we get regarding the Gilbertson PVC Bluebird & Small Bird House.    Also, we have answers to common questions regarding how to attract bluebirds and other birds to nesting boxes, as well as problem solving common issues.

Q:  I’ve had my bird house up for several weeks and no birds have come to check it out.   What is the problem?

A:  There may be no problem.  Sometimes it can take a long time for birds to find a new nest box and use it.  If it’s later in the nesting season, many birds may have already found a suitable nesting site.  Also, what may seem like a good location to us, may not be to birds.  If there is no activity for several more weeks, try moving it to a new location.

Q.  I don’t want sparrows to nest in my box, but how do I tell a sparrow nest from a bluebird nest?

A.  Sparrows fill the entire box with a mixture of sticks, grass, plants, feathers, trash, and other debris.   Bluebirds on the other hand build a tighly woven nest made up almost entirely of grass and sometimes pine needles.  The nest probably sits 2 to 2 1/2″ high.  Also, bluebird eggs are light blue, whereas sparrow eggs are whitish with brown flecks.  Below, the bluebird nest is on the left, sparrow nest on the right:

Bluebird nest with eggsHouse sparrow nest with eggs

Q.  I’ve put up the Gilbertson box, but House Sparrows have still gone into it.  What should I do?

A.   Unfortunately, no bluebird house design has been developed that is 100% resistant to house sparrow (HOSP) incursions.  Sometimes there are sparrows that are more persistent than others or there are simply so few other nesting choices for them, they will still choose the Gilbertson box.  There are a number of actions you can try to try and get them to go away, but remember that it may be a trial and error process until you find a strategy that works.

First, try moving the box to a more open spot further away from any dense cover, feeders, outbuildings, or your home.   Also, make sure to plug up any crevices or open spaces on the exterior of your house to prevent sparrows from nesting there.  Examples are vents, gaps behind siding, crevices between board, etc.

Second, you can remove the lower section of the house for several days to see if the sparrows leave to look for another nesting spot.

Third, persistent removal of the sparrow nest/eggs may work after a while.  Or they may just keep rebuilding the nest.

Fourth, put up a 2nd more “standard” wooden box in the vicinity of the Gilbertson house.   In almost all cases, the HOSP’s will choose the standard wooden box to nest in.  However, if you do this, it is still strongly advisable to “evict” them from this house via trapping since they could still harass or attack the bluebirds in the Gilbertson box.   Remember that house sparrows are non-native, invasive species of birds that are not protected by federal or state laws.  So, you are free to trap/euthanize or shoot them if that is something you want to do.  However, you should always make sure there are no local ordinances that may affect these activities.  You can buy a sparrow trap made for the Gilbertson house on this site.  Click Here.

Fifth, a method that has had success in preventing house sparrow incursions is hanging two weighted 18″ lengths of fishing line or thin wire on either side of the entrance hole (about 1 1/2 to 1 3/4″ away) by afixing them to the edge of the roof with small tacks or nails.  You can use medium sized washers or fishing sinkers to weight the ends of the line.  This forces the birds to fly between the lines to enter the box.  Bluebird don’t mind doing this, but sparrows dislike it.  This method mainly works BEFORE the sparrows have claimed the box.  If you try putting them up after the sparrows have claimed the box, it will be less effective.

Sixth, if you’re feeding the birds, stop putting out seed until the nesting season is over.  Sparrows like birdseed and having it in your yard will increase the number of sparrows that are then likely to take over nest boxes.

 Q.  The bluebirds came in and built a nest, but now I haven’t seen them for a while.  What happened?

A.  It’s hard to say.  The birds may have found another nesting site nearby and chose that one.  Or something could have happened to one or both of the birds.  It’s OK to leave the nesting material in the box.

Q.  It’s almost the end of spring and I still haven’t gotten bluebirds to nest.  Is it too late to attract them this year?

A.  Not at all.  Depending on the weather and natural food supplies, bluebirds can have 2 or even 3 broods in a single season.  It’s very common to have them nesting in June and July, and even into August sometimes.

Q.  How can I protect my nesting box from climbing predators?

A.  First, all pole mounted nesting boxes are vulnerable to climbing predators like snakes, raccoons, opossums, and all types of squirrels.  The smooth metal pole is NOT enough to stop them from climbing up the pole.  You can try greasing or waxing the pole. This will be effective for a short time.  But eventually, the wax or grease will need to be reapplied and unless you’re vigilant in monitoring that, the box will be vulnerable again to predation.  A better method is to put a metal predator guard on the pole.  These can be either a metal shield type or the more common stove-pipe type.  (See the picture of one you can build yourself).  The stove type baffle is usually made of steel or aluminum, is about 24″ long, and from 6 to 8 inches in diameter.  These baffles are effective because the metal is smooth, can’t be chewed or provide a way for claws to get a grip, and are too wide for animals to shimmy up.  The baffle rests on a collar that makes it “tippy”.  This helps make the baffle harder to get by.  Baffles can be purchased commercially or you can make one for about $10 – $12 in material from the home center.  You can download a free PDF article MakeABaffleArticle that explains how to make one.

Q.  I checked my nest box and found all white eggs in the box, yet I know bluebirds are nesting there.  What is going on?

A.  Although most bluebird eggs are light blue in color, about 5-10% of them are white.  This is normal and nothing to be concerned about.

Q.   I’ve had a pair of bluebirds trying to nest, but a pair of swallows showed up and have been trying to chase the bluebirds away.  What can I do about this?

A.  Tree swallows and Violet Green Swallows (two species that nest in bluebird houses commonly) are native birds who are perfectly fine to have around.  But, a potential solution to this problem is to put up a 2nd nest box about 8 to 10 feet away.  The swallows will usually allow the bluebirds to nest in peace in one box, while they nest in the other one.  In this case, the swallows will also chase away other swallows that show up.

Q.  I put up my Gilbertson PVC nest box just like you said, but I noticed it keeps turning in a strong wind.  Is there some way to stop it from doing this so I can see the entrance hole more easily?

A.  Yes.  Sometimes the hole in the roof that receives the conduit pole can be a little loose.  There are a couple ways to solve this issue.  One is wrap the top of the pole with a little tape of some kind to snug up the fit.  Another solution is simply drill a hole through the 2×2 piece under the roof into the conduit pole.  Then, screw in a short wood screw to prevent any further turning.  A 3/4″ screw should be enough.

Q.  I keep finding my bluebird house filled with small sticks.  Is it bluebirds doing this or some other bird?

A.  This is almost certainly a House Wren nest.  House Wrens are tiny, brown birds that prefer brushy or thicket-filled habitats.  The male will often fill up every nesting cavity (including bird houses) in his territory with sticks, and then let a prospective mate choose one of them for an actual nest.  So, most of these stick-filled cavities will end up being dummy, unused nests.  Dummy nests (those with no eggs or lining of grass/mosses in the bottom) can be removed.  But because unpaired male wrens can exhibit destructive behavior to other birds eggs and hatchlings, it’s advisable to move your bluebird house away from dense cover to more wide open locations that are less attractive to wrens.

 Q.   We live in a very hot climate and I’m concerned about this nesting box getting too hot for the young and adults.  Is there anything I can do? 

A.   Yes.  You can put a “heat shield” over the roof that will help reflect more solar rays, provide more shade, and help keep the inside of the box cooler.  Make the shield out of 1/4″ plywood about twice as large as the roof of the house.  Cover the shield with heavy aluminum foil.  Then attach the shield to the roof with a couple short wood screws.

Q.   Should I clean out my bluebird house at the end of the nesting season?

A.  Yes.   If the house was nested in, it will likely be filled with wet, used nesting material, some droppings, and possibly insect parasites.  Remove all this material and scrub the house out with water and a brush.  Then let it dry before storing it for the winter.

Q.  I found a baby bluebird below the box and it’s still alive.  What should I do?

A.   If the bird appears healthy and OK, try putting it back into the nesting box – (NOTE:  this assumes the rest of the brood of young is still in the box and are OK)  Then watch for a little while to see if the adult birds are still coming by to care for the young.  If there is no activity for an hour or two, something may have happened to the female bluebird, or even both adults.  In this case, the only alternative will be to locate a local licensed wild bird rehabilitator, and take the birds to him/her.  DO NOT attempt to try and care for and feed the young birds yourself.  You may end up doing more harm than good.

Q.  How should the roof be installed on the Gilbertson Bluebird house body – there’s two ways to do it? 

A.  Put the body on the roof mounting screws with the entrance hole on the opposite side from the 2 X 2 mounting bracket with the hole.  See the picture below:

Mounting Gilbertson Bluebird House


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Cornell Lab of Ornithology