Building Tree Swallow Nest Boxes

Why do Tree Swallows use nest boxes?

Cavity-nesting birds like Tree Swallows, that can't make their own cavities,
usually face a shortage of nest sites.
Competition for cavities can be intense, even a matter of life and death, since
failing to reproduce is a critical failure for short-lived songbirds.
Tree Swallows must compete for nest sites with other Tree Swallows and also
with other cavity-nesters like bluebirds, wrens, starlings and house sparrows.

Since natural cavities are scarce Tree Swallows quickly accept nest boxes, and
unlike many other cavity nesting species they aren't picky! They'll use just
about any box they can get into.
Tree Swallow nests have been found in large houses for Purple Martins, Wood
Ducks and Screech Owls, and in such unlikely spots as drain pipes, mailboxes
and newspaper tubes (see the photo below by Laura Niang in Maryland).
Sadly, they'll also try to nest in unsuitable tiny or flimsy boxes where few if any
young survive.

Be sure to build boxes designed specifically for Tree Swallows.

You'll want boxes built carefully of good materials, where your swallows will be
safe from predators and protected from rain and heat, ones roomy enough so
parent swallows can raise strong, healthy young.

WE RECOMMEND THE FOLLOWING TWO TREE SWALLOW DESIGNS:

Click this link the plan for the GOLONDRINAS BOX. This box (see below) is easy
to make and is used by scientists of the Golondrinas de las Americas (Swallows
of the Americas) project coordinated by Cornell University.
The Golondrinas project is a unique hemisphere-wide effort conducting
research into the comparative biology, ecology, and behavior of Tree Swallows
and the eight other species in genus Tachycineta.
Thousands of Golondrinas Boxes are in use at the 50 or so research sites
throughout North and South America (see map).
If you decide to make Golondrinas boxes we have two suggestions. Make the
top wider and longer for increased protection against bad weather and
predators, and be ready to block the ventilation openings on the upper sides
during cold windy and rainy spells (see below).

Click these links for the LONG POINT BOX: INCHES or CENTIMETERS. This is
the box pictured below and elsewhere on this web site.
We saw this design at the Long Point Bird Observatory in Ontario, Canada, liked
it, and modified it a bit. It differs somewhat from the Golondrinas Box and is
harder to make, but we've used it at Salmon Creek since 2003 and are very
satisfied.
The above links take you to printable files containing introductions to the Long
Point Box and its features, construction suggestions, and a detailed plan for
cutting and assembling these boxes.

No matter what design you use all Tree Swallow boxes should have:

Sturdy wood construction using 1" rough-cut boards or exterior-grade plywood
at least 1/2" thick.
1-3/8" to 1-1/2" entrance holes to keep larger birds out.
Entrance holes centered about 7" above floors.
Floors never smaller than 5" x 5".
Roofs that slope down and overlap sides and fronts, reducing exposure to rain
and making it harder for predators to reach inside.
Sides that swing open for easy checking of box contents and cleaning.
Floors recessed to minimize interior wetness.
Unpainted interiors.
Roughened, kerfed, or cleated front interiors to provide nestling footholds.
No outside perches at the entrance holes that could aid predators.

WARNING! DON'T MAKE OR BUY BOXES THAT ARE TOO SMALL!

Many published box plans and boxes sold in stores are intended for bluebirds,
which although larger than swallows average fewer nestlings per brood.
Recently some bluebird hobbyists have advocated using very small boxes in a
well-intended but futile attempt to prevent box use by House Sparrows.
DON'T use these boxes for Tree Swallows! They often have interior
dimensions that are far too small for swallow broods of up to seven young.
You may meet people who say the small bluebird boxes are just fine for Tree
Swallows. They are NOT ok! While it is true Tree Swallows will eagerly accept
small boxes, their nestlings may not thrive or fledge successfully.
Boxes with small internal volumes put nestlings at risk of death from
overheating during hot spells because the nestlings can't spread out to cool.
Smaller nestlings may get trampled by larger siblings, have their feathers soiled
with feces, and be unable to reach food brought by parents.
Swallow nestlings also require space to exercise their wings so they can fly
strongly when they fledge, and it's possible lack of space may even interfere
with proper bone and feather development.
Imagine six or seven swallow nestlings trying to survive in the tiny bluebird
tube below! (Photo from Craig A. Mullenbach of Mully410*Images*).

Nest boxes with small interiors can also be detrimental to adult swallows.
Note the badly damaged flight feathers of the swallow below that nested in a
small bluebird box. (Photo used with permission of Charles G. Summers, Jr.).

To avoid potential problems be certain your floors are at least 5" x 5".
Narrow, cramped designs like the Peterson, Gilbertson, Gilwood, and Troyer
Bluebird Boxes are totally unacceptable in a Tree Swallow project, and in our
opinion the North American Bluebird Society and any of its member clubs and
individuals that continue to promote the use of boxes with small interiors
show a blatant disregard for the lives of other native songbirds.
The same dimensions and standards apply if you purchase kits or ready-made
birdhouses. If you plan to buy from a store, bring a ruler along. Many of the
boxes you'll find will be too small for Tree Swallows (no matter what the clerk
says). If they don't measure up (literally), don't buy!
Compare the four nest box floors below. Which provide enough space for the
typical brood of six tree swallow nestlings shown? They are 12 days old and
must stay and develop inside their box for another six to ten days before they
can fledge safely. How many would you think could survive in the two lower
bluebird-type boxes?

But why would Tree Swallows ever attempt to nest in such cramped boxes?

We really don't know why. They certainly don't seem to use "selective
judgement" in their choices.
Perhaps the shortage of natural cavities drives the tendency of Tree Swallows
to accept anything they can claim. But since we know they will use them, we
should never put out miserable little death traps like many bluebird designs!
And what about bluebirds? They're even larger than Tree Swallows! How could
boxes with tiny interiors possibly be better for bluebirds? If this question
interests you, click here to read Linda Violett's treatment of the subject.
The fact is that the larger-interior box designs we recommend for Tree
Swallows are also very acceptable for bluebirds, and for many years 5" x 5"
interiors were standard for bluebird boxes. (However, if you use the
Golondrinas or Long Point box and live in Mountain Bluebird range, make your
entrance holes 1-9/16" to allow them to enter).

Don't be afraid to improvise.

Since Tree Swallows are so very accepting in their choice of box designs you
can be creative, just as long as you follow the minimum size guidelines
presented above.
For example note the clever box below, designed and made by Irena of Ottawa,
Canada. It features feeding holes that can be opened to prevent one large
nestling from monopolizing the food supply, a flip-up roof overlap, and a hinged
side door. It is waterproofed on all outer surfaces except the front with
candle wax, first rubbed on and then melted in with a heat gun. If you would
like to try her design, click here: IRENA'S SWALLOW BOX.

Consider installing a Nest Camera inside a box.

Tree Swallows are so easy to watch we sometimes forget many vital behaviors
and actions occur inside their nesting cavities. But the advent of tiny remote-
control cameras presents you the opportunity to view even those.
We have never used nestcams ourselves, but we know persons who have
enjoyed them tremendously, who've spent many fascinating hours observing
live video on their TV's or computers as their swallows built nests, incubated
eggs and raised young.
To get a sense of what can be seen using nestcams click here for the Cornell
Lab of Ornithology's NestCam site. Be sure to visit Explore Archives.
To learn about nestcam hardware and installation click here for the bluebird
hobbyist web site Sialis' excellent page on the subject.
Be aware you may have to tweak your box design to accommodate a nestcam.

How many boxes should you build?

The best number depends on your habitat's quality, the size of your field, and
your energy and budget.
4 to 8 boxes is good for starters. That's enough so you can see how individual
swallows vary in behavior and nesting, but not so many that record keeping
and box maintenance is a chore.
But if you want to start with just one that's perfectly ok. Just start. If you
enjoy your swallows (and we know you will) you can always expand next year.
Picture below from Jennifer Stanley in Kentucky.